Britain's Anti-submarine Capability 1919-1939 (Cass Series: Naval Policy and History)

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BRITAIN’S ANTI-SUBMARINE CAPABILITY 1919–1939

Copyright © 2003 George Franklin

CASS SERIES: NAVAL POLICY AND HISTORY Series Editor: Geoffrey Till

ISSN 1366–9478 This series consists primarily of original manuscripts by research scholars in the general area of naval policy and history, without national or chronological limitations. It will from time to time also include collections of important articles as well as reprints of classic works. 1. Austro-Hungarian Naval Policy, 1904–1914 Milan N.Vego 2. Far-Flung Lines: Studies in Imperial Defence in Honour of Donald Mackenzie Schurman Edited by Keith Neilson and Greg Kennedy 3. Maritime Strategy and Continental Wars Rear Admiral Raja Menon 4. The Royal Navy and German Naval Disarmament 1942–1947 Chris Madsen 5. Naval Strategy and Operations in Narrow Seas Milan N.Vego 6. The Pen and Ink Sailor: Charles Middleton and the King’s Navy, 1778–1813 John E.Talbott 7. The Italian Navy and Fascist Expansionism, 1935–1940 Robert Mallett 8. The Merchant Marine and International Affairs, 1850–1950 Edited by Greg Kennedy 9. Naval Strategy in Northeast Asia: Geo-strategic Goals, Policies and Prospects Duk-Ki Kim 10. Naval Policy and Strategy in the Mediterranean Sea: Past, Present and Future Edited by John B.Hattendorf 11. Stalin’s Ocean-going Fleet: Soviet Naval Strategy and Shipbuilding Programmes, 1935–1953 Jürgen Rohwer and Mikhail S.Monakov 12. Imperial Defence, 1868–1887 Donald Mackenzie Schurman; edited by John Beeler 13. Technology and Naval Combat in the Twentieth Century and Beyond Edited by Phillips Payson O’Brien 14. The Royal Navy and Nuclear Weapons Richard Moore 15. The Royal Navy and the Capital Ship in the Interwar Period: An Operational Perspective Joseph Moretz 16. Chinese Grand Strategy and Maritime Power Thomas M.Kane 17. Britain’s Anti-submarine Capability, 1919–1939 George Franklin


Britain’s Anti-Submarine Capability 1919–1939

GEORGE FRANKLIN

FRANK CASS LONDON • PORTLAND, OR


First published in 2003 in Great Britain by FRANK CASS PUBLISHERS Crown House, 47 Chase Side, Southgate London N14 5BP and in the United States of America by FRANK CASS PUBLISHERS c/o ISBS, 5824 N.E.Hassalo Street Portland, Oregon, 97213–3644 Website: www.frankcass.com Copyright © 2003 George Franklin British Library Cataloguing in Publication Data Franklin, George D. Britain’s anti-submarine capability 1919–1939.– (Cass series. Naval policy and history; 17) 1. Anti-submarine warfare—Great Britain—History 2. Great Britain—History, Naval—20th century I.Title 359.9'3'0941'09042

ISBN 0-7146-5318-7 (cloth) ISSN 1366–9478 Library of Congress Cataloging-in-Publication Data Franklin, George D. Britain’s anti-submarine capability, 1919–1939/George D.Franklin. p. cm.—(Cass series-naval policy and history; 17) Includes bibliographical references and index. ISBN 0-7146-5318-7 (cloth) 1. Anti-submarine warfare—Great Britain-History-20th century. 2. Great Britain. Royal Navy-History—20th century. I. Title. II. Series. V214.F73 2003 359.9'3–dc21 2002035056 All rights reserved. No part of this publication may be reproduced, stored in or introduced into a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher of this book.


Some were brave, some were not, all were human. To the men who went to sea and faced the U-boats. But, first among them, to my father. As he asked us to write on his gravestone CAPTAIN RICHARD FRANKLIN CBE RN MARINER


Contents

Page List of Illustrations

viii

List of Figures and Tables

ix

Series Editor’s Preface

xi

Acknowledgements

xiii

List of Abbreviations

xv

Introduction

1

1

Strategy

9

2

Organisation

28

3

Sensors

57

4

Weapons

72

5

Platforms

87

6

Tactics

112

7

Wartime Experience

162

8

The System

176

Conclusion

186

Appendix A: Theory of Asdic

191

Appendix B: Portland Exercise Success Criteria

196

Bibliography

198


Illustrations

Between pages 80 and 81 1. Bridge repeaters and asdic communications on a destroyer, c. 1932. 2. A 1922 photograph of HMS Rocket’s asdic control position. 3. A First World War hydrophone operator training the equipment to obtain the bearing of a contact. 4. HMS Rocket’s transducer. 5. Retractable streamlined dome for type 121 asdic. 6. Asdic control position on a trawler. 7. A Sa Ro London small flying boat. 8. Pre-war Avro Ansons flying in formation. 9. Two A/S bombs fitted to a Sa Ro London. 10. Short Sunderland flying boat. 11. Marshal of the Royal Air Force Lord Trenchard. 12. Marshal of the Royal Air Force Sir Arthur Harris. 13. Admiral of the Fleet Lord Chatfield. 14. Captain ‘Jonny’ Walker directing an attack. 15. HMS Stork. 16. HMS Ibis. 17. HMS Enchantress. 18. HMS Stork. 19. Loading a depth-charge thrower. 20. A depth charge in the air, having been fired from its thrower. 21. Detonation of a single depth charge. 22. Anti-submarine nets during the Seawolf trials. 23. HMS Seawolf on the surface, after having become entangled during indicator net trials. 24. Heavy anti-submarine nets being laid near Rosyth for the Seawolf trials.


Figures and Tables

FIGURES Page 1. Sea Lords and Sections of the Naval Staff Concerned with AntiSubmarine Warfare. 29 2. Employment of Specialist A/S Officers, and Total Personnel Strength of the Navy. 39 3. Type 114 Asdic Set, Showing Typical Arrangement of Equipment. 59 4. Depth Charge Thrower. 74 5. Standard Depth Charge Pattern. 74 6. Depth Charge Chute. 76 7. Depth Charge Rail. 77 8. The Submarine Approach Problem. 119 9. Asdic Sweep Pattern. 122 10. Battle Fleet Asdic Screen for Exercise RZ, August 1933. 138 11. Convoy Night Asdic Screen for A/S Defence only: Exercise MA, 1929. 144 12. Percentage of Success Rates in Asdic Hunting Exercises, 1925–38. 157 13. Subaqueous Sound Paths. 194 TABLES 1. 2. 3. 4. 5. 6. 7. 8.

Bearing and Requirement of A/S Specialist Officers, 1922. Training of A/S Officers at Portland, 1935–38. Training of SD Ratings at Portland, 1929–38. Depth Charge Armaments, 1939. Escort and Patrol Vessel Particulars. Particulars of A/S Vessels Built 1919–39. Convoy Defence Exercises. Ships Sunk in Convoys, 3 September 1939–31 May 1940.


Page 35 36 43 79 92 95 114 169

Series Editor’s Preface

In his charmingly modest memoirs1 Admiral Harris Laning, US Navy, reflecting on his time at the US Naval War College in the early 1930s, refers to the widespread view that sailors are intrinsically resistant to new ideas, often through having some ulterior motive. In Laning’s time, the particular complaint was that hidebound battleship admirals were reluctant to admit the extent to which technology in the shape of aircraft and submarine was threatening the traditional primacy of the all-big-gun battleship. This view has also been adopted by a number of scholars, especially amongst those who proceed on the basis of a set of generalisations derived from the social sciences about how innovation does, or does not, take place. Most obviously a new technology comes along and is eventually accepted. It becomes part of the naval establishment. This creates a generation of naval officers with experience of this new technology; partly for career reasons, and partly because they cannot shake off attitudes absorbed in their most formative years, they become a vested interest, defending their now accepted paradigm of naval warfare against even newer challenges coming along in their turn. Almost by definition therefore, naval officers will be a generation behind the times. The only comfort is that their enemies will be too—mostly.2 Often such scholars are able to make use of the views of naval officers connected with the new technology, disappointed at the slow rate at which their ideas have been adopted—or, even worse, furious that they have been rejected altogether. In the case of the Royal Navy of the inter-war period, such views have even heavily influenced the conclusions of its great and much respected semi-official historian Captain Stephen Roskill who argues in his Naval Policy Between The War3 that the British Admiralty of the time did indeed concentrate too much on the conduct of major fleet battles at sea, wanting in particular to re-fight the Battle of Jutland; they did pay too little attention to the impact of airpower at sea and, most dangerous of all, they did neglect the unglamorous demands of the defence of shipping. And even when such conservative admirals were concerned about the defence of shipping, they focused on the wrong kind of threat to it—surface raiders not submarines.


BRITAIN’S ANTI-SUBMARINE CAPABILITY, 1919–1939

This historical debate about the way that conservative naval hierarchies delay the process of adaptation has a good deal of modern salience as we move into a new century of naval operations at sea. Today, there is much talk about the ‘transformational’ impact of new technology, especially in the shape of computers and micro-processors, and much worry that modern sailors are not responding to such challenges effectively and may well be caught out by it later, as their predecessors were. Against this litany of complaint of and concern, Laning pleaded for a degree of realism and of understanding: Those critics fail to realize that naval officers, more than anyone else, want to win our wars at sea and care little as to the kind of weapon used, only that it be legal and bring victory. For that reason, they try out every device, every method, and every suggestion, but advocate only those with satisfactory results. The writings and talks of columnists and others unacquainted with sea warfare or with the practical utilization of sea weapons cannot convince the navy to adopt unproven ideas. The navy tries every new, feasible, and worthwhile suggestion, hoping to find more certain ways to win a war. It does not however accept neophyte suggestions. Navies always have to deal with the challenges of new technology, and the best policy, he argued, was one of ‘steady as she goes’—cautious, open-minded, pragmatic and incremental adaptation when the evidence that major change is necessary is finally convincing. In this book, George Franklin, a serving naval officer himself, explores the Royal Navy’s attitude to anti-submarine warfare in the interwar period. His conclusions will challenge many of the existing stereotypes about ‘naval conservatism’ and offer much support for the views of Admiral Laning. He finds that the Admiralty approach towards the submarine threat was much more balanced and sensible than it is often given credit for. He shows that the innovation process is a complicated one and that only by realising such complexities and by avoiding the seductive appeal of simple solutions will navies be able effectively to respond to technological challenge. NOTES 1 2

3

Admiral Harris Laning, An Admiral’s Yarn (edited by Mark Russell Shulman), Naval War College Press, Newport, RI, 1999, pp. 327–8. W.M.McBride, Technological Change and the United States Navy 1865–1945, Johns Hopkins University Press, Baltimore, MD, 2001, is an example of this kind of approach. Several previous volumes in this series have attacked such simplistic ideas, notably Phillips Payson O’Brien, Technology and Naval Combat in the Twentieth Century and Beyond and Joseph Moretz, The Royal Navy and the Capital Ship in the Interwar Period. Stephen Roskill, Naval Policy Between the Wars (2 vols), Collins, London, 1968 and 1976.

xii Copyright © 2003 George Franklin

Acknowledgements

Without a shadow of doubt my first and greatest acknowledgement must go to Evan Davies. Faced with the frankly thankless task of teaching history to tired cadets at the Britannia Royal Naval College, Dartmouth, he lectured with sufficient zeal to arouse an interest which had lain dormant since my school, criminally, allowed me to drop history at the age of 12. He has since never failed to encourage me and to offer constructive advice based on his compendious knowledge of the twentieth-century history of the Royal Navy. Neither my departure to sea nor his from Dartmouth interrupted his help, and it is entirely his fault that articles, book reviews, an MPhil. thesis and this book have been written. I am, and I will always remain, immensely in his debt. A good deal of this book is based on primary research, so I have the staff of a number of archive sources to thank. First must be the Keeper of the Records and the staff at the Public Record Office, whose efficiency, helpfulness and excellent use of IT contribute to the PRO’s status as a national asset of which Britain can rightly be proud. Among the staff of the Archives Centre at Churchill College, Cambridge, the Naval Museum at Portsmouth, the Naval Historical Branch of the Ministry of Defence in London, the National Maritime Museum at Greenwich, the Imperial War Museum, the Naval History Sections of Portsmouth and Plymouth Public Libraries, and the National Library of Scotland, I have encountered nothing but patience and support. During one stage of the book’s metamorphosis it took the form of an MPhil. thesis, so it is only right to acknowledge the cheerful and tactful guidance provided by my two supervisors, Professor Evan Mawdsley and Dr Phillips O’Brien, both of the University of Glasgow. Lieutenant-Commander Jock Gardner, who in his capacity at the Naval Historical Branch has already had an oblique mention, also deserves my thanks for taking a nervous and entirely ignorant new author by the hand during the first stages of the publishing process. In this regard Professor Geoffrey Till of the Joint Services Command and Staff College also deserves, and gets, my gratitude.While we are with the Ministry of Defence I must thank Commander Mike Mason, who as the Royal Navy’s Head of Defence Studies supported the project in ways that I had not dreamed possible.



Claire Westall and her various flatmates deserve special mention, for consistently putting me up in Chelsea while I was researching in London, and my sister Cecilia, who despite a fundamental lack of interest in naval history was good enough to check the book for readability, gets the prize for endurance. All errors or shortcomings are, of course, my own, and are not to be associated with those who have been kind enough to help me. As a serving officer I need to make the point that, although the book has been approved for publication by the Ministry of Defence, it was written with minimal official support or encouragement, and the conclusions are my own, not those of the Ministry or any associated official body. Finally, and perhaps bizarrely, I have to thank the staff of Café Citrus in Southsea, Steinbecks at Chelsea and Westminster Hospital, Patisserie Florentine in Edinburgh, Café Cofea in Soho, the Kew Hot House in Kew, Café Rouge in Cheltenham and the Palais des Sables in Les Sablettes. None of them knew it, but the chap who sat in the corner spending very little money and scribbling on bits of yellow paper was writing a history book, and has now finished it.

xiv Copyright © 2003 George Franklin

Abbreviations

AL A/S 1 A/S ACNS AFO ARL Asdic C in C Capt. A/S Capt. D2 CB CHURCH CID

Admiralty Library Anti-submarine First Anti-Submarine Flotilla Assistant Chief of the Naval Staff Admiralty Fleet Order Admiralty Research Laboratory, Teddington Submarine detection equipment, now called sonar Commander-in-Chief Captain in charge of anti-submarine matters Captain Commanding Second Destroyer Flotilla Confidential Book (Classified Admiralty Publication) Churchill College Archives Centre Committee for Imperial Defence, subcommittee of the Cabinet CNS Chief of the Naval Staff CO Commanding Officer D of P Director of the Plans Division of the Naval Staff D of TD Director of the Tactical Division of the Naval Staff D2, D8 etc. Second, Eighth, etc. Destroyer Flotillas DC Depth Charge DCNS Deputy Chief of the Naval Staff DDA Dived Danger Area DOD Director of the Operations Division of the Naval Staff DSD Director of the Signal Division of the Naval Staff DSR Director of Scientific Research IWM Imperial War Museum JPC Joint Planning Committee MNBDO Mobile Naval Base Defence Organisation MRCS Medium Range Constant Speed NCS Naval Control of Shipping NML Naval Museum Library NMM National Maritime Museum


ABBREVIATIONS

PRO RA(D) RA(S) RAF RN RNR RNVR RUSI SDA 1SL 2SL TDZ

Public Record Office Rear-Admiral Commanding Destroyers (one in each fleet) Rear-Admiral Commanding Submarines Royal Air Force Royal Navy Royal Naval Reserve Royal Naval Volunteer Reserve Royal United Services Institute Surfaced Danger Area First Sea Lord Second Sea Lord Torpedo Danger Zone

xvi Copyright © 2003 George Franklin

Introduction

History has shown time after time the fatal results of basing Naval or Military strategy on an insecure line of communications. Disaster is certain to follow, and our present policy is heading straight for disaster, and it is useless and dangerous in the highest degree to ignore the fact. If we do not recognise this fact, and shape our policy accordingly, it is my firm conviction that we shall lose the war.1 Despite the experience of the First World War that had made clear the lethal potential of German undersea warfare, and the buildup of Nazi military might in the 1930s, the British and American anti-submarine defences were inadequate and their weapons virtually useless. Seen in this light the final victory over German aggression and technical skill was a major triumph.2 Not one exercise in the protection of a slow mercantile convoy against submarine or air attack took place between 1919 and 1939.3 During the First World War the German submarine campaign against British trade in the Atlantic came very close to bringing the British Empire to its knees. It became evident to the Royal Navy, and to the country as a whole, that the methods being employed against submarines were unsatisfactory, and after an extended debate the system of convoy was introduced.This was substantially successful, and reduced massively the rates of losses to submarines. Parallel to the development of convoy, and other anti-submarine tactics, came investigations into weapon systems, sensors, suitability of platforms for antisubmarine work, and a debate about the efficacy of conducting forward defence by bombing the U-boat bases. Many works have been written about the period 1914–19, and in matters of anti-submarine warfare over the period little controversy remains. When the Second World War started in 1939 Britain very quickly found 1 Copyright © 2003 George Franklin


its trade routes once again under attack from a rebuilt German submarine service.The Battle of the Atlantic lasted from the first to the last months of that war and saw much inventiveness in tactics, strategy and material development. There is a widely held belief that the inter-war years were wasted by those sections of the Royal Navy which were charged with responsibility for anti-submarine warfare. This school holds that there were no properly formed plans to introduce convoy in 1939 and the navy as a whole believed that the introduction of asdic, initially developed before the armistice but never operational during the first war, had robbed the submarine of its advantage of invisibility. The submarine menace, they argue, was thus considered to have been mastered, and detailed analysis of anti-submarine tactics could be dispensed with; as a result of overconfidence in asdic, therefore, little or no work was done to prepare to defend against submarine attack. The first fully authoritative works to be published covering the interwar period were S.W.Roskill’s two volumes, Naval Policy between the Wars. Roskill had achieved great success in his official history of the war at sea, during the writing of which he was allowed unattributable access to unreleased official papers, and through this he had achieved an oracular status among those interested in the naval history of the period. That status remains, deservedly, largely in place today. When Roskill wrote, then, that ‘not one exercise in the protection of a slow mercantile convoy against submarine or air attack took place between 1919 and 1939’, this seemingly extraordinary assertion was taken, without question, as fact. Subsequent writers have been content to quote this as the final word on the period. One thus emerges with a picture of an inter-war navy which, having developed asdic, was content to ignore anti-submarine matters and get on with the rather more entertaining business of cocktail parties and battle fleet exercises.When war comes, and the Germans make a submarine attack on Atlantic trade, the navy is to be found blowing dust off 1919 documents, learning how to do it all again, and doing extraordinarily well under the circumstances. Clearly there have been some more reasoned analyses than this, but the broad gist remains consistent. Peter Padfield, for instance, talks of the Royal Navy’s ‘neglect of the necessary protection for merchant shipping against submarine—and indeed air—attack’. He finds that ‘undoubtedly, faith in Asdic played its part’.4 As evidence of this neglect, he goes on to cite Roskill’s contention that no exercises in the protection of slow convoys took place between the wars. John Terraine makes the same quote from Roskill, and goes on to allege that the Admiralty was ‘hypnotised’ by the success of asdic, calling on Roskill for further substantiating evidence.5 Willem Hackmann also cites Roskill’s ‘not one exercise’ statement but concedes that ‘there is some evidence, however, that the Admiralty did consider this problem and conducted at 2 Copyright © 2003 George Franklin

INTRODUCTION

least one slow convoy exercise’.6 In common with Vice-Admiral Sir Arthur Hezlet,7 he notes that a 1932 review found that the Royal Navy’s capacity for anti-submarine defence of mercantile trade was unsatisfactory, and that escorts could not reliably detect submarines before the first merchant ship was attacked. Once the submariner had revealed himself, however, the escorts had a good chance of counter-attacking to sink or at least drive off the submarine. Correlli Barnett, refreshingly, does not quote Roskill, but does note that faith in asdic’s performance led the Admiralty to believe that the submarine menace had been largely mastered.8 Clay Blair, in a very detailed 1997 history of the U-boat war, writes that the Royal Navy ‘had not pursued Asdic vigorously’9 between the wars, and further tells us that ‘not until December 1938, when the Germans advised Great Britain that they would build to submarine parity, did the Admiralty begin serious planning for the possibility of a U-boat war’.10 According to Arnold Hague the Admiralty ‘publicly claimed that [asdic] had defeated the submarine even though it was untested in other than theoretical investigations’, but adds that private doubts about its effectiveness spurred inter-war preparations for convoy.11 Dan Van DerVat, writing in 1988, found that asdic ‘led to a dangerous complacency about submarines, including almost total neglect of antisubmarine tactics’.12 He goes on to make the by now familiar quote from Roskill, also alleging that although ‘from 1933 all destroyers had Asdic, less happily, very little practice was acquired with it’. As a result of this failure to practise with the equipment, it was not until after the beginning of the war, he claims, that it was discovered that asdic was prone to giving false contacts, performed poorly against surfaced targets, degraded when the ship was at speed, could not determine submarine depth, and had a minimum range of some hundreds of yards. This opinion has spread beyond the literature into general acceptance. Admiral Sir Roderick MacDonald KBE, giving a speech on the Battle of the Atlantic at the Naval Club in 1991, told his audience that ‘there is no record of any exercise in the protection of a slow convoy against submarine or air attack between 1919 and 1939’ and went on to talk of the Royal Navy’s ‘unjustifiable reliance on a primitive underwater sound detection system even though U-boats had attacked on the surface in World War I’.13 The intention of this book is to test the validity of these contentions, by studying the development of the Royal Navy’s anti-submarine capability between the armistice and the German invasion of France.Taking a thematic approach to that development, we will look at the organisation that directed the development, the training of the men, the procurement of sensors, weapons and platforms, and the evolution of tactical doctrine. First, though, we will look at the strategic imperatives that drove the pace of development and the level of resources allocated to it. It seems that little can be gained by a study of inter-war work without making some reference to at least the 3 Copyright © 2003 George Franklin


early months of the war to determine if the methods adopted were in fact successful. The wartime period has been terminated in June 1940 for two main reasons, the first being that all inter-war strategic planning for a war against Germany made the assumption, at the highest level, that France would not fall.The navy, therefore, planned for a war with an ally across the channel, a war during which German submarines would have to make a long and dangerous transit before operating in the deep and open waters of the Atlantic. From July 1940 the Germans operated from the ideally placed Biscay ports, so could take the battle to the mid-Atlantic with an ease not envisaged by strategic or tactical planners in the inter-war period. It seems hardly reasonable, therefore, to judge inter-war anti-submarine development against the test of a war which the Admiralty were told not to expect.14 The second reason is that, not surprisingly, methods and equipment did evolve as war experience grew, and the techniques employed by both sides after the summer of 1940 resembled less and less those used in the early months of war. The wartime study will take the form of a close examination of interactions between German submarines and Royal Navy anti-submarine vessels to establish the success of the anti-submarine methods employed. Although some study will be made of the period from the armistice to the mid-1920s, the bulk of the work will concentrate on the 15 years before the start of the Second World War. The reasons for this are twofold: first, there was very little tangible progress made in the immediate aftermath of the Great War, and, second, the whole organisation was in a state of considerable flux as the navy contracted after the armistice, and only became effectively rationalised in the mid-1920s. Readers who come to the subject without a moderately firm grasp of what asdic was, how it worked and how oceanographic conditions could affect its performance are advised to familiarise themselves with Appendix A before plunging into the meat of the book. On the subject of abbreviations, acronyms and initials, I have tried where reasonable to avoid their use, but the reader must be prepared for two which will recur repeatedly, A/S for anti-submarine, and CID for the Cabinet subcommittee known as the Committee for Imperial Defence. The process of development of military tactics in time of peace follows a predictable pattern. First, a strategic analysis is made of the conflict for which one is preparing; then tactics are designed and exercised, in an iterative and continuous process. Once satisfactory tactics have been developed for the weapons, sensors and platforms currently available, it is usual to enter into a discussion process with other specialisations to ensure that there is no compromise with the requirements of other branches. A plan to stay close to the support of one’s own shore batteries, for instance, may have to be compromised to meet the requirement to stay in deep water to avoid enemy mines. Once the service has accepted the theory of a tactic it is then published and integrated into the operating procedures of the relevant arms of the 4 Copyright © 2003 George Franklin

INTRODUCTION

service. Throughout this process the strategic planners should be kept informed of the current state of development and the anticipated capabilities and limitations in the relevant field, in order that war plans may be properly devised. Faithful to this process, there will be an attempt throughout the book to address five core questions: 1.

2. 3.

4. 5.

Did the anti-submarine organisation of the Royal Navy make thorough studies of the likely tactics and strategy of the anticipated enemy, and were the results of these studies realistic? Did the exercises and trials carried out test the conditions anticipated, and did they prepare personnel for the anticipated war? Were the wider navy, the relevant sections of the air force, and policy makers outside the services kept aware of progress in, and limitations of, antisubmarine capability? Were the procedures developed by the anti-submarine specialists understood by, and integrated into the operating procedures of, the wider navy? Did the conditions anticipated actually materialise?

The reader will note that these questions refer almost wholly to tactics, while the book promises to study the development of the whole capability.While the approach will be to examine the entire system, the ultimate test of that system, in peacetime, must be the development of tactics, of which the building blocks are described in Chapters 2 to 5, namely personnel, sensors, weapons and platforms. There are very few published works dealing in any detail with the Royal Navy in the inter-war period, and as discussed above the majority of those that are available follow, almost slavishly, Roskill’s line. Initial research among primary sources indicated that the provenance of Roskill’s evidence may be limited, and so reduced the reliability of the majority of the secondary sources. The book is therefore almost exclusively based on primary source material. The most lucrative source was the Public Record Office, most notably the ADM 116 series of Admiralty papers and the 186 series, which includes reports of progress from the anti-submarine establishment at Portland and a selection of post-exercise reports. Useful material was also found at the Admiralty Library in the Naval Historical Branch, London, whose partly unindexed collection contains material which nicely fills gaps in the PRO material. Personal papers were drawn from the Naval Museum Library in Portsmouth, the archives centre of Churchill College, Cambridge, the Maritime Museum, the Imperial War Museum, and the Submarine Museum in Gosport. Serving officers of the time have also been consulted, including Admiral Sir Ian McGeoch, who was a pre-war submariner, Admiral Sir Antony Morton, who served in wartime destroyers, Captain Barrie Kent RN, expert on the history of naval communications, and LieutenantCommander David Waters RN, a prewar Swordfish pilot and instructor 5 Copyright © 2003 George Franklin


who co-authored the Staff History of the Second World War U-boat campaign. It may appear later in the book that I have set out deliberately to attack Roskill, and I wish to make it clear that this is not the case. I am keenly aware that only by standing on the shoulders of giants can I see so far, and it is only because the bulk of what Roskill wrote retains such authority that his few shortcomings are worth investigating. His books on inter-war policy remain the unchallenged standard works, and have thus been relied on heavily, especially in the first chapter. Similarly, Hackmann’s excellent technical history of the development of asdic, which is unlikely ever to be surpassed as a source, has been used extensively in Chapter 3. There are two broad subject areas which have not been included, and their omission demands an explanation. The first is the use of submarines in the anti-submarine role. Some mention has been made of asdic systems which were developed for submarines, and of the training of submarine A/ S personnel, but the procurement of the boats and their tactical employment have not been mentioned.This is largely because the only weapon available to the submariner was the torpedo. His asdic sensor could give no accurate indication of the depth of the target so he could not set torpedoes to run at a given depth against a dived submarine, and he could thus only fire against a surfaced submarine, or at best against one that was at periscope depth. The tactics of the submariner chasing another would only differ from those that he would have used against a surface ship in that he would use active rather than passive asdic, and sufficient has already been written about the general subject of submarine, rather than anti-submarine, warfare to make its inclusion in this book unnecessary. Further, the fact that at the time it was impossible to communicate with a submarine that was below periscope depth meant that submarines could not be properly integrated into escort or attack groups. The only RN submarines specifically built for A/S operations were the ‘R’ class, which were given a high underwater speed, but these were all out of service by 1939. The second omission is any mention of matters financial. Joseph Maiolo writes that ‘the whole subject of Royal Navy ASW [anti-submarine warfare] between the wars, that is the dynamics of interaction between technological progress, doctrinal evolution, finance and the quality of training, is…deserving of its own study’,15 and while I clearly agree that the study is worthwhile, I found that the introduction of finance made it necessary to tie in too many other factors. A/S development, as it stands, has proved relatively easy to isolate and to treat as a discrete system, but the introduction of finance threatened to change this. To talk in absolute terms about sums of money is meaningless, so the money spent on A/S would have to be compared with the sums spent on trade defence cruisers, battle fleet units, submarines and, ultimately, RAF and army equipment and training. This would then necessitate discussion of the relative merits of these other subjects, 6 Copyright © 2003 George Franklin

INTRODUCTION

and the book would begin to sprawl out of control. Further, the reader will discover that Admiralty policy with regard to A/S for trade defence was to develop prototypes and industrial capacity in order to allow for expansion in war.The peacetime establishment, therefore, was never intended to match the wartime requirement. Battleships, cruisers, aircraft and such like were, however, built in peacetime to the levels required for war, so comparison of the sums spent on A/S with those spent on other naval capability areas would produce a misleading impression. Finance has thus been largely omitted, other than where it refers to comparison between A/S assets. Finally, I feel obliged to add a note of personal defence. The general conclusion of this book is that the civil servants, scientists, officers and seamen who worked between the wars on ways to combat submarines did not do a bad job. There were, of course, shortcomings, and in highlighting these I have tried to explain, rather than excuse. This approach puts me in direct conflict with the vast majority of published works on the subject, some of which reproduce Roskill’s contentions as detached historical fact, and some of which, in search for readership, take a salacious pleasure in highlighting and exaggerating the alleged shortcomings without putting them in context. The human conclusion, after all, that we could have done better than those in charge, rarely fails to give a form of psychological satisfaction. I am keenly aware that, written as it is by a serving officer rather than an academic, there is a risk that this book will be discounted as the work of a naval apologist.This is not the case. It is not my experience of public service that the stupidest people get promoted. Nor is it my experience that, having been promoted, they dedicate themselves to chasing foxes and watching cricket. By extension, I do not see why that should have been the case in the 1920s and 1930s, especially given that the navy was then far more important to the nation than it is today. I am therefore unwilling to accept boneheadedness as an explanation for policy decisions, and where possible I have sought to put those decisions into their appropriate context, showing them from the perspective of the men who made them. I have found some straightforward errors of judgement, but I have also found that a lot of what appears from a distance to have been stupidity turns out, on close examination, to have made good sense at the time. NOTES 1

Jellicoe, as First Sea Lord, to the War Cabinet, ADM 1/8480/36, The Submarine Menace, 21 Feb. 1917. 2 Edwin P.Hoyt, The U-boat Wars, Robert Hale, London, 1985. 3 Stephen Roskill, Naval Policy between the Wars, Collins, London, 1968, Vol. 1, p. 536. 4 Peter Padfield, War Beneath the Sea: Submarine Conflict 1939–1945, John Murray, London, 1995, p. 23.

7 Copyright © 2003 George Franklin

BRITAIN’S ANTI-SUBMARINE CAPABILITY, 1919–1939 5 6 7 8 9 10 11 12 13 14

15

John Terraine, Business in Great Waters: The U-boat Wars 1916–1945, Leo Cooper, London, 1989, see esp. pp. 177–8. Willem Hackmann, Seek and Strike: Sonar and the Royal Navy 1914–1954, John Murray, London, 1995, p. 131. Vice-Admiral Sir Arthur Hezlet, The Electron and Sea Power, Peter Davies, London, 1975, p. 178. Correlli Barnett, Engage the Enemy More Closely: The Royal Navy in the Second World War, Hodder & Stoughton, London, 1991, p. 45. Clay Blair, Hitler’s U-boat War: The Hunters, 1939–1942, Weidenfeld & Nicolson, London, 1997, p. 26. Ibid, p. 71. Arnold Hague, The Allied Convoy System 1939–1945: Its Organisation, Defence and Operation, Chatham, London, 2000. Dan Van DerVat, The Atlantic Campaign: The Great Struggle at Sea 1939–1945, Hodder & Stoughton, London, 1988, pp. 55–67. IWM 92/4/1, Speech given at the Naval Club, Hill St, Mayfair, 17 May 1991, in the papers of Admiral Sir Roderick MacDonald KBE. While it might seem naïve of the Admiralty to have based all planning on France resisting German attack, one must remember that departmental estimates will only be approved by the Treasury if they are based on the assumptions given to the respective department. An Admiralty request, therefore, for funds to finance construction of extra ships against the contingency of France falling would have been turned down on the grounds that they were planning outside the strategic assumptions. Joseph A.Maiolo, The Royal Navy and Nazi Germany, 1933–39: A Study in Appeasement and the Origins of the Second World War, Macmillan Press, London, in association with King’s College, London, 1998, p. 121.


1

Strategy

1919–23:THE NEW WORLD ORDER The makers of Britain’s foreign and defence policies faced many challenges between the wars, and much has been written about their responses to these challenges. The object of this chapter is not to produce yet another analysis of this broad and important subject, but to focus solely on those matters which had direct influence on the business of anti-submarine warfare. In this way the rest of the book can be placed in its proper strategic context. The approach taken will be chronological, dealing first with the immediate inter-war period, then the period of perceived Japanese threat.The last section will cover the years following the Anglo-German Naval Treaty of 1935, when it became evident that German submarines were once again likely to threaten the United Kingdom’s sea communications. Although the introduction stated that the general study would start in the mid-1920s, anti-submarine matters having advanced little in the years immediately after the armistice, the early period has been included in this chapter. Thus we will see how, and why, having come close to strangulation at the hands of the German submariners in 1917, and having used light forces to pull victory from the teeth of defeat, the Royal Navy lost no time in reasserting the primacy of the big gun ship. The negotiations which followed the armistice, first between the allies and later including the central powers, were fraught with difficulties, not least in the naval sphere.The proposals for the disposal of the German Fleet were many and diverse, though of course in the event the Germans took care of much of that problem themselves by scuttling the ships in Scapa Flow. One subject which caused little controversy, however, was the fate of the German submarines, the bulk of which were either broken up or sunk, with a few passing to the allies for ‘propaganda or research’ purposes. Thus the only submarine fleet likely to pose a threat to Britain’s communications



was done away with, and its owners were specifically forbidden to develop any sort of submarine warfare capability. This, of course, left other navies, notably the French, in possession of submarines, and the Admiralty initially tried to get around this difficulty by having submarines declared illegal. After some persuasion the Americans came round to agree to this, but none of the other seafaring nations would entertain the proposal. Given the nature of the submarine as the weapon of the weaker power which could threaten elements of even the greatest battle fleet, it was unsurprising that general agreement was not reached. Admiral de Bon of the French navy may have summed up the feelings of many of his colleagues when he described attempts to outlaw the submarine as being ‘contrary to good sense’. He went on to declare that the weaker powers should be able to keep submarines to defend themselves so long as they were used in accordance with the laws and customs of war.1 Herein lay the rub for the Admiralty; a nation which engaged in lawful, or restricted, submarine warfare could probably be mastered without excessive loss, but one which employed unrestricted tactics, as had the Germans during a good part of the war, could cause grave difficulties.2 The Anglo-American proposal was not adopted, but the subject was to become a recurrent theme at naval conferences throughout the 1920s and early 1930s. Early post-war operations had little or no requirement for anti-submarine involvement.The war of intervention in Russia, which ran until November 1920, was mainly a business of coastal motor boats, shallow draught river craft and the occasional bombardment. Certainly, the Bolsheviks were never in any position to threaten with submarines. Similarly, the Royal Navy’s heavy commitment, from 1919 to 1923, to the war between the Greeks and Turkish nationalists consisted almost entirely of bombardment and the landing of shore parties, and was conducted without submarine opposition. The nature of these two operations, the Royal Navy’s first real involvements in the supposed new world order, may have encouraged the belief that the submarine was no longer a serious menace. These overseas expeditions were never likely to lead to serious attacks on the nation’s lifelines, such as had been experienced during the Great War, and even those minor powers which possessed a submarine capability would gain little more than a propaganda coup from attacking the fleet. In addition, Beatty, as First Sea Lord, represented a commonly held faith when he declared in 1920 that ‘the latest type of capital ship is so well protected that she can be hit by a considerable number of the most effective torpedoes now existing without being sunk’.3 With the professional head of the service thus advertising the fleets’ invulnerability, there can have been little motive to pursue developments in anti-submarine techniques. There remained, however, an awareness of what the Germans had done to Britain’s merchant fleet and warships during the war, and efforts to master the submarine did continue, albeit on a theoretical basis and without a specific enemy in mind. 10 Copyright © 2003 George Franklin

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The post-war honeymoon was, however, not to last long, and a potential submarine threat soon emerged in the Far East.The Japanese had increased the extent of their possessions during the Great War, and the strategic significance of this spread was not lost on the Admiralty. In 1919 Jellicoe found, on a tour of dominion navies, that the main threat to Australia and New Zealand was Japanese, and in the same year the sloop HMS Veronica was sent to survey various Pacific islands and make recommendations about possible future oiling bases. Jellicoe’s report to the Admiralty, though, which described Japan as ‘the nation with which trouble might conceivably arise in the future’4 was but the first hint of a nascent concern, and afforded the matter no great urgency. At around this time the CID was studying the same problem. Among other conclusions, they felt that the most suitable vessels for the dominion navies to operate would be submarines and cruisers.5 This implied very strongly that a war in the Pacific would be an offensive campaign against the enemy’s trade, and indicated an expectation of early sea control. The logical corollary of such an argument was that protection of imperial trade, and thus anti-submarine measures, would take a low priority. The period following the armistice was characterised by a steady cooling of Anglo-Japanese relations, but the pivotal point came in the after math of the 1921–22 Washington naval conference, which fundamentally changed the relationship. The conference was, however, originally conceived as an arms limitation exercise, and before discussing its wider diplomatic implications it would seem sensible to touch on those technical conversations which related to anti-submarine warfare. The vast majority of the naval limitation discussions undertaken at the conference, and most of the conclusions reached, revolved around capital ship and cruiser tonnages, armaments and numbers. Flotilla vessels were only fleetingly touched on, but Britain did once again attempt to have the submarine banned altogether. In the case of the Washington talks, however, this was more of a negotiating position than a realistic hope, and indeed Beatty minuted before the conference that ‘it is certainly not to be expected that the submarine will be totally abolished’. After a brief controversy over an article in which Capitaine de Frégate (Commander) Castex, principal lecturer at the French Senior Officers’ Course, seemed to approve the unrestricted use of submarines, a measure was introduced which sought to limit the conduct of submarine warfare. This statement, later known as the ‘Root resolution’, asserted that submarines were not ‘under any circumstances exempt from the rule of “visit and search”’.6 Inactual fact, French failure to ratify the relevant part of that treaty meant that the Root resolution had no place in law, but it still had potential as an instrument of political pressure. It is evident that throughout the conference Britain’s delegation felt that the main threat to trade routes came from surface raiders and not submarines. 11 Copyright © 2003 George Franklin


Bids to be allowed to build ships for trade defence were therefore centred on cruisers and the arming of merchantmen as auxiliary cruisers. One can conclude, rather unexcitingly, that the naval limitation discussions at the Washington conference were only minimally concerned with submarine or anti-submarine warfare, and throw little light on the core themes of this book. Of greater significance for us, however, were the strategic and diplomatic discussions. The Royal Navy had been intimately involved in the development of the Imperial Japanese Navy virtually from its inception in 1868, and the mutually beneficial relationship between the two navies was formalised with the signing of the Anglo-Japanese Alliance of 1902, which was renewed in 1905 and 1911. Direct Japanese support for the Royal Navy during the First World War was limited, although the Japanese seizure of German colonies in the Far East probably did no harm to Britain’s cause in Europe, and Japanese ships did carry out some escort duties in the Mediterranean and the Far East. In the eyes of many Royal Navy officers, however, British aid to the Japanese had been rather more concrete during the Russo-Japanese war, and by 1918 there was a growing feeling that the Japanese navy, having come of age, was becoming less inclined to hang on to its teacher’s coat tails. This erosion of the patron-client relationship between the two navies, and Japan’s growing independence, lessened the Alliance’s importance to Britain and, by the time the delegations reached Washington, the Admiralty regarded it as being little more than a bargaining chip. Indeed, to some within the Admiralty, keen to establish an enduring liaison with America, the Alliance was becoming a liability. When the Foreign Office asked their Lordships for their feelings on the subject in 1920, they received the reply that ‘[the Admiralty] consider a continuation of the Alliance in its present form neither necessary nor desirable’.7 The Japanese were reluctant to accept the limitations on their warship tonnages proposed by the conferences, and one of the means of persuading them to settle for the 5:5:3 ratio between Britain, America and themselves was the signature of the Four Power Pact. Under the terms of this pact, between Britain, Japan, America and France, Britain was prevented from fortifying any Far East base other than Singapore, and the Americans were not to fortify any bases west of Hawaii. The Japanese, for their part, could fortify their home islands and the island of Manus, to the north-east of Borneo, but were prevented from protecting any of their other Pacific possessions. The significance of these accords was that Hong Kong, the Philippines and other British and American territories were ‘left at the mercy of the Japanese’,8 while Britain and America were left with no bases from which they could attack Japan. This was clearly to Japanese advantage, but the awkwardness in the agreement came in the concluding words, inserted to quell American fears of an aggressive Anglo-Japanese presence in the western Pacific. The American condition was that ‘this 12 Copyright © 2003 George Franklin

STRATEGY

agreement shall be ratified as soon as possible…and thereupon the agreement between Great Britain and Japan…shall terminate’.9 Reluctantly accepted by Japanese negotiators, this abrogation of the old alliance was seen at home as a slap in the face from Britain, and, if it did not directly influence policy with regard to Britain, it certainly weakened the influence of the pro-British moderates within the navy. There was no dramatic turning away from friendship, but the effectively unilateral abrogation signalled the beginning of a period of cooling relations, and ushered in an era during which Japan ceased to be a support in the Far East, and became instead a threat and a rival. A second consequence of the Four Power Pact, as seen from London, was that the Americans, lacking a fortified base in the western basin of the Pacific, came to rely on the Royal Navy to act as the first line of defence against potential Japanese aggression.10 Whether or not this was actually the case, the perception that, at least in the early stages of a conflict, Britain would stand alone against Japan, buttressed the position of those in London who felt that the Admiralty should look east in its search for a role. Thus, by 1923, the strategic shifts that had followed the armistice had settled down to provide a fairly clear picture. War with America—despite the naval rivalry that informed many policies on either side of the Atlantic, and the existence of theoretical American plans for a war against the British Empire—was inconceivable. Germany, given the Versailles limitations on its naval development, and the fact that its navy had been dismantled, presented no sort of threat to the Royal Navy. The Air Ministry saw France, with its supposedly huge air attack capability, as the main threat to the UK. Further, French insistence at Washington on the maintenance of its substantial submarine and cruiser forces, which might have allowed a profitable attack on Britain’s trade routes, had led to a cooling of Anglo-French naval relations. Notwithstanding these factors, however, the diplomatic position dictated that France was not a country with which the Royal Navy expected to find itself at war.This left the Japanese.They had increased their possessions during the war, and had at Washington successfully secured themselves sufficient capital ship tonnage to threaten American Pacific domination and Britain’s eastern Empire.They had, under the Four Power Pact, consolidated their position in the Pacific and ensured that they were able to fortify Manus, so providing strategic support well away from their home base. Finally, whatever Japan’s essentially pragmatic diplomats thought of the abrogation of the Anglo-Japanese Alliance, Britain’s action in siding with America gave the Japanese leadership an opportunity to manipulate anti-British public feeling. In mid-1923 Admiral Sir John de Robeck, C in C Atlantic Fleet, was told that he was to lose his five Queen Elizabeths, probably his most powerful ships, to the Mediterranean Fleet.This was clearly in recognition of the fact that it would be the Mediterranean Fleet that, in an emergency, would sail 13 Copyright © 2003 George Franklin


east to meet the Japanese threat.The Admiralty letter told the Commanderin-Chief that ‘with the disappearance of Germany as a naval power the Western Pacific has become the area to which all eyes are turned’.11 Japan had, by 1923, clearly emerged as the main naval threat to the empire. 1923–35:THE PRIMACY OF THE JAPANESE THREAT Financial stringency and the requirement to maintain fleets in European waters meant that there was never any ambition to have a force comparable to the Mediterranean and Atlantic Fleets permanently based in the Far East. Japanese aggression would be met by the sailing of, essentially, the Mediterranean Fleet to the Far East.The linchpin of subsequent operations would be the proposed Singapore base, an enormous undertaking that would include fuelling and repair facilities, an aerodrome, accommodation and all necessary defences against direct Japanese attack. The critical period in such a war, especially if the Japanese were to achieve strategic surprise, would clearly be during the main fleet’s four- to six-week transit. The base could, during this time, expect to encounter long-range bombardment, blocking operations, direct invasion and, of greatest interest to us, submarine attack. Colonial and dominion navies were generally expected to play their parts in the defence of their regional waters, and, while the precise details of their contributions and the integration of their navies were the subject of frequent negotiations, the general principle was agreed. Clearly, Australia and New Zealand could not be expected to provide large numbers of main fleet units, and the solution was to invite them to operate smaller ships, some of which were donated by the Royal Navy. A system was also introduced in dominion and colonial navies which, during the late 1920s and early 1930s, allowed them to develop Royal Naval Volunteer Reserve (RNVR) services which in time of war might man flotilla craft. Unfortunately, both the dominion navies and the various RNVR schemes concentrated heavily on minesweeping, and there is no evidence of their developing anything other than the most rudimentary anti-submarine capability. Thus, in the weeks before the arrival of the main fleet with its anti-submarine destroyers, the Japanese submarine force would be opposed only by the ships of the China station, whose life expectancy when faced by the Imperial Japanese Navy could not have been great.12 Debate about the best way to defend Singapore continued until the MacDonald Labour government rather moved the goalposts on 18 March 1924. On that date the Prime Minister announced to parliament his government’s belief that they ‘could not ask Parliament to go on with this [Singapore] scheme’ which ran counter to the Labour philosophy of achieving global security through negotiation rather than the use of arms. 14 Copyright © 2003 George Franklin

STRATEGY

That government, however, proved to be short lived, and at the end of October the Conservatives, under Baldwin, were returned to power. Baldwin’s Cabinet lost no time in re-addressing the problems of imperial defence, and on 26 November 1924 Cabinet ‘approved that the Singapore naval base should be proceeded with’.The pendulum had not yet, however, finally come to rest. In early 1925 the Bridgeman committee was set up to examine naval expenditure. When they asked the CID whether war with Japan was likely during the next ten years they were told that the CID agreed with Foreign Secretary Sir Austin Chamberlain’s conclusion that it ‘was not a contingency to be seriously apprehended’.13 Proposals for a reduced and somewhat delayed programme to develop the Singapore base continued, and in mid-1925 it was decided that the anti-submarine defence of the base area was to be completed by the end of 1929, the other defences coming later. One suspects, however, that the priority thus given to antisubmarine defences owed more to the fact that they were a good deal cheaper than heavy guns and aerodromes than to any consideration of defensive priorities. Having established the primacy of the Japanese threat, and looked broadly at Britain’s stance, it is worth taking some time to look at how the Japanese planned to use their submarines in war, and how this influenced specific A/ S policies.14 Japanese naval planning was based on the assumption that the decisive moment in a future Pacific war would be a cataclysmic naval clash, after the pattern of Trafalgar or Tsushima. This battle would be fought against the Americans or, less probably, the British, and would give the victor total effective control of both Pacific basins. Such was the importance of this battle that other naval functions, such as an attack on exposed trade routes, were subordinated to it.Virtually all submarine training was thus aimed at direct support to the battle fleet, and attack on trade was hardly thought of, let alone planned. This was not the case in the early days of the Japanese submarine force, when the wartime experience of officers who had helped provide antisubmarine escorts for allied ships heightened awareness of trade’s vulnerability to submarine attack. The original intention to use submarines against merchantmen as well as warships was soon abandoned though, because, among other reasons, ‘there was little interest in doctrine advocating destruction of the enemy’s sea communications because the destruction of the enemy’s battle fleet was crucial and such a difficult problem’.15 A further factor may have been the Bushido code, to which, though less enthusiastically than the army, the navy did subscribe. Under this code the submarine warrior’s proper task was to fight warriors in warships and other submarines; there was little glory and no honour in attacking unarmed and defenceless merchant ships. Furthermore, it has been argued that the Japanese planners, already partly hypnotised by their own success at 15 Copyright © 2003 George Franklin


Tsushima, read completely the wrong lessons from the First World War. U9’s success in sinking HM Ships Aboukir, Cressy and Hogue in September 1914 achieved a mythological status, and the much feared but in fact ineffective U-boat trap at Jutland was held up as an example of how submarines could support a battle fleet. Meanwhile, little was made of the attack on trade which had almost crippled Britain. Commander, later Admiral, Nobumasa Suetsugu cannot have helped this situation. Having been assigned to the Royal Navy as an observer during the 1914–18 war he went on to spend the inter-war years advocating the use of large submarines to conduct a campaign of attrition against battle fleets. Indeed, one recent source has Suetsugu, as a submarine squadron commander and then a staff planning officer in the mid-1920s, developing the ‘attrition strategy…[that] assigned to large, high speed submarines the important mission of wearing down the enemy’s main fleet’.16 Suetsugu’s rise, through the posts of Assistant Chief of the Naval Staff and Commander-in-Chief of the Combined Fleet, to Minister of Home Affairs (from 1937 to 1939) will have done little to erode the influence of his views. By the time war broke out the fantastic claim that the submarine force could sink 30 per cent of the American Fleet as it transited the Pacific was going unchallenged, and in these circumstances it seems hardly surprising that trade attack was, at best, a secondary role. No evidence has been found of deliberate attempts by the British Naval Staff to study Japanese war plans, but it would be very surprising if the close links between the two navies did not give the Admiralty a good idea of Japanese operating philosophy.17 A 1933 paper on the nature of the threat in the Far East did specify that the naval responsibilities consisted of The provision and operation of a main fleet in the Far East sufficient to meet the Japanese Fleet at her selected moment; and, secondly, behind the cover of this main fleet, the protection of our sea communications… Our shipping would be exposed to attack by enemy cruisers, submarines or merchant ship raiders.18 The subsequent discussion, however, revolved entirely around the surface threat, no further mention being made of submarines. A later paper on the requirement for A/S vessels in the event of a Far East war specified that the main initial effort of the Imperial Japanese Navy would be against the bases at Hong Kong and Singapore and the main fleet as it entered the theatre. No mention was made of the need to protect trade routes. One has to consider therefore that, although the Admiralty were planning for a war in the Far East during which trade routes would have been very vulnerable, analysis of the enemy’s anticipated tactics would have indicated that the threat to these routes came from cruisers and the battle fleet. Defence of those routes against submarine attack, therefore, did not need to be given a high priority as they were threatened not by submarines but by a considerable cruiser force as well as the Imperial Japanese Navy’s battle fleet. 16 Copyright © 2003 George Franklin

STRATEGY

This does not mean to say that there would be no role at all for antisubmarine forces in a Far Eastern war. Far from it, in fact.The anticipated Japanese attack on the main fleet was taken very seriously. A paper by the Director of the Tactical Division, in which he outlined destroyer requirements in various foreseen conflicts, showed that for fleet A/S protection in the event of a Far East war a staggering seven and a half flotillas, each of eight ships, would be required.19 Emphasising the fact that the Admiralty was at the time very much looking to the east, the same paper said of a European war that ‘In this case it is more difficult to form an estimate of the numbers [of destroyers] required, owing to the fact that no European power possesses a Battle Fleet comparable to our own: a fleet action is therefore unlikely’ The submarine menace from France and other powers, however, still forced a requirement of seven asdic-fitted flotillas to protect the battle fleet in the event of a purely European war. In the early 1930s, however, there were no asdic-fitted ships in the China squadron, and it was only with the arrival in 1934 of HMS Grimsby, a newly built convoy sloop, that asdic established a permanent presence in this independent command. Later in that year the new ‘D’ Class asdic-fitted destroyers of the 21st flotilla joined the China squadron, giving the Royal Navy, for the first time, an effective A/S capability permanently based in the Far East. Although, superficially, it seems odd to have left the Far East without an A/S capability until 1934, the China squadron was only intended to demonstrate Britain’s continued interest in the region, perhaps quelling the occasional colonial bush fire. It was never meant to stop the advance of the Imperial Japanese Navy. The retention of A/S expertise in the Mediterranean Fleet was entirely consistent with the ‘Main Fleet to Singapore’ policy, which would allow for defence in strength against all forms of attack, once that fleet had arrived. Further, if the submarine threat in the Far East was to the battle fleet rather than to trade, it would have made little sense to keep large numbers of destroyers and flotilla vessels in theatre in preparation for a trade defence campaign. Rather, the A/S forces which would protect a fleet should be kept with that fleet in order to develop the instinctive reactions in mutual support that would be so important in battle. It should be borne in mind that the bulk of the fighting strength of the Royal Navy was, throughout the period under consideration, divided between the Atlantic (later Home) Fleet and the Mediterranean Fleet. The Commander-in-Chief of the former was, before the emergence of the German threat, free to concentrate on some rather theoretical studies of the way a future war might be fought. The Commander-in-Chief of the latter, who would carry the responsibility for war with Japan, would have been much more focused on preparation for a very possible conflict against a very tangible enemy. The reader will therefore notice, particularly in Chapter 6, differences between the approaches of the incumbents of the 17 Copyright © 2003 George Franklin


two posts. This was even the case when, as occasionally happened, admirals passed from command of one fleet to command of the other.20 Even after Hitler’s accession to power, and his 1933 declaration that Germany would leave the League of Nations and withdraw from disarmament talks, Japan remained the major preoccupation for those who were planning for the next war. The Defence Requirements Committee, established in November 1933 to review the nation’s preparedness for war, thus based its initial plans on the assumption that, although Germany posed the greater long-term menace, the short-term requirement was to develop a Far Eastern capability which might deter Japanese aggression.21 This was certainly the case for the anti-submarine community, given that Germany still had no declared submarine capability. Indeed, a 1933 CID paper gave that the only circumstance in which Britain could face a European submarine threat was the unlikely situation of being forced by obligations under the Locarno Treaty to go to war against France.22 This was further confirmed a year later when another CID paper stated that ‘There is, at present, no serious indication of German naval construction at variance with the [Versailles] treaty provisions.’23 The authors of this report went on to say that there was little likelihood of a major German submarine menace developing in the near future. British intelligence agencies were in receipt of reliable information about German submarine construction almost as soon as the effort started. The relevant files remain classified, but it is certain that Dr Otto Krueger, for one, was keeping London informed of Germany’s clandestine submarine programme both during his time at IvS24 and later in the Kiel shipyards.25 Although other sources remain obscure, files do survive that indicate that German efforts to hide their U-boat developments substantially failed, and in the light of this it seems odd that the CID should be talking of ‘no serious indication of German Naval construction’. The key word here, though, was ‘serious’.While it was accepted that some capability was being developed, it was thought in the early 1930s that Hitler’s submarine arm would be limited by industrial and training capacity, so would not be capable of rapid development. Indeed, the CID paper cited above specifically mentioned the probability of a training bottleneck, a factor which impeded development long after the signature of the Anglo-German Naval Agreement. The question of whether to configure against a Japanese or German threat became more complicated with time, the first change being the emergence of the German bomber threat to the United Kingdom. This resulted in an assessment that the most serious air threat came from Germany, but the major maritime threat remained Japan, and the navy continued to plan on that basis. By 1935, however, the international situation had deteriorated to such an extent that the Defence Requirements Committee was authorised by the ministerial Defence Priorities and Requirements Committee to 18 Copyright © 2003 George Franklin

STRATEGY

‘reassess the defensive needs of the country without regard to financial consideration’.26 1935–39:THE RE-EMERGENCE OF THE GERMAN SUBMARINE THREAT It is, of course, impossible to name a date on which Germany overtook Japan as the main concern for the Admiralty. Indeed assessments vary from Van DerVat, who asserts slightly dubiously that the German navy was ‘the overriding concern of British maritime strategy’ from 1904 until 1945,27 to Gordon, who has the Admiralty looking east right up until Munich.28 There is no doubt that the CID was beginning to look towards Germany in the early 1930s, a 1933 paper, in the splendid lexicon of imperial government, describing Germany as ‘once more manifestly becoming a public menace’.29 A slightly later paper by the Chiefs of Staff Committee concurred in this view, stating that it was ‘no longer possible to allow the Far East entirely to absorb our attention as might perhaps be inferred from our review of 1930’. 30 The Defence Requirements Committee, when it first reported in 1934, specifically stated that ‘The greatest potential threat lies in the acquisition of submarines and aircraft by Germany…she no doubt intends to build up a submarine force.’31 As far as anti-submarine matters are concerned, however, the shift can probably be said to have taken place after the 1935 Anglo-German Naval Agreement, which forced acceptance that the Germans were likely once again to be able to mount a submarine attack on the Royal Navy and Britain’s trade routes. Under the terms of this agreement, which departed from Versailles and broke the Stresa Front,32 Germany was allowed to build up to 35 per cent of Britain’s naval strength, with a clause allowing them, under certain circumstances, to build up to 100 per cent of the Royal Navy’s submarine strength.33 In the wake of the agreement, the First Sea Lord reported to the Defence Requirements Committee that the German submarine building programme allowed for the construction of 20 coastal boats and eight ocean boats in 1935, being followed by a further ten ocean-capable boats the following year.34 Certainly, by 1937 there was no attempt to hide from the fact that the growing U-boat arm represented a very real threat both to the Royal Navy and to the maritime trade routes.The Chiefs of Staff, reporting to the CID in November of that year, pulled no punches in telling their masters that ‘We must be prepared for unrestricted attack by submarines against our trade, more particularly by Germany.’35 They were, however, able to assure the politicians that measures to protect trade were well advanced. Specifically, all existing destroyers without asdic were shortly to have it fitted, the Kingfisher type patrol vessel and the Basset class Admiralty trawler had been developed and were ready to be mass-produced on the outbreak of war, 19 Copyright © 2003 George Franklin


200 further trawlers had been earmarked for A/S duties, and trials of asdicfitted high-speed motor boats were shortly to take place.36 Analysis by the Joint Planning Committee, whose membership included the heads of the three individual service planning divisions, estimated in 1936 that the Germans would, by September 1939, be able to operate between 56 and 66 U-boats. This prediction turned out to be startlingly accurate, given that Dönitz actually had 56 available at the beginning of the war. Using this assessment the Chiefs of Staff predicted that there would normally only be around ten on patrol at any time. In another very accurate prediction, they conceded the possibility of an all-out early attack, but said that this would, necessarily, be of only short duration and would be followed by a lull as the boats returned to harbour.37 It was admitted that an unrestricted submarine attack would cause substantial early disruption to trade, but it was felt that a repeat of the situation in 1917 was unlikely because ‘instruments for detection’ had been improved and widely fitted, aircraft had been integrated into A/S operations in a way not achieved in the Great War, and preparations for convoy, which were at an advanced stage, would allow the system to be introduced early and with the minimum of disruption. In mid-1938 the early vulnerability was again emphasised when Chatfield, soon to be replaced as First Sea Lord, specified that it would take About three weeks to commission the ships of the reserve fleet, together with the necessary destroyers and auxiliary craft required for trade protection. In the intervening period we should have to face the possibility of losses from submarine attack or air attack.38 A slightly earlier CID paper had outlined the plans and the perceived situation with particular reference to submarine attack on trade. In this paper it was specified that ‘in recent years there has been considerable progress in the tactical and technical development of anti-submarine methods’,39 which was incontrovertibly true. It was given that ‘once a submarine is detected, her chances of ultimate escape should not be great’,40 which, provided there were asdic escorts in the vicinity, was to prove the case in the early months of the war. This paper also stated, quite explicitly, that ‘In the case of unrestricted warfare, convoy will be adopted and all A/S vessels available will probably be required as escorts.’ It must not be supposed that, after 1935, the possibility of war with Japan disappeared altogether; indeed, avoidance of simultaneous war against Japan and Germany was the preoccupation of British foreign policy makers in the mid- to late-1930s. It was still thought in the Admiralty that a naval war against Japan would revolve around battle fleets and, increasingly, aircraft carriers, and in October of that year the First Sea Lord reported to the Defence Requirements Committee that the navy ‘should be able to send to the Far East a Fleet sufficient to provide cover against the Japanese fleet’.41 A paper prepared by the Chiefs of Staff for the CID in 1937 once again 20 Copyright © 2003 George Franklin

STRATEGY

indicated that trade defence, particularly against a submarine attack, would not be a major consideration in a war against Japan: In the Far East, Japanese local naval strength would render unrestricted attack by submarines unnecessary north of Hong Kong, and the distances involved would probably render it ineffective elsewhere… The geographical situation of Japan relative to the countries of the British Empire and the principal sea routes of the world is unfavourable for sustained operations by the Japanese against British trade and communications as a whole.42 The first analysis, that the Japanese would enjoy total sea control to the north of Hong Kong, and that the sea to the south of Hong Kong was too far from their home bases for their submarines to operate, makes good sense until one considers the possibility that they might capture bases further south.The fall of Singapore was, like the fall of France, not a circumstance to be contemplated, but Hong Kong, vulnerable since the Washington Treaty had forbidden its fortification, was not expected to last long in the face of a Japanese attack.There were also question marks over the ability of the French to resist a Japanese attack on Indochina.The fall of Hong Kong would have put Singapore and the Indonesian shipping routes within 600 nautical miles of a Japanese base, and the capture of French Indochina could have halved that range. One can, therefore, only justify the Chiefs of Staff (COS) committee’s argument on the grounds that, as discussed earlier, Japanese submarine doctrine dictated that they should attack warships, not trade routes. The second part of the analysis, essentially saying that the Indian Ocean was too far away from Japan to be attacked, seemingly ignored the Far Eastern successes of Kiel-based German raiders in the early part of the Great War, but was clearly applicable to submarine attack. The analysis so far has only considered the position with regard to Germany and Japan. Italy, however, did have a substantial submarine force, the Abyssinian crisis brought Italy and Britain close to war, and a state of war did finally exist between the two countries from June 1940. It would seem important, therefore, to consider how the Admiralty considered the Italian threat and to what extent manning, training and procurement policies were informed by perceptions of the Italian menace. Italy’s status at the end of the First World War, and its contribution to the Versailles debates, placed it unequivocally as a friend of the United Kingdom. Mussolini’s dramatic rise to power ruffled some feathers in London, but the Foreign Office’s collective eye remained firmly fixed on Japan. Furthermore, Mussolini lost little time in declaring his friendship, and, whatever retrospective value one puts on his promises, there was at the time little reason to think they were anything other than genuine. Italy’s participation as a guarantor of Locarno in 1925 was necessary if the treaty was to have any coherence, and it has been argued that Italy’s inclusion thus had more symbolic than actual value. It was nonetheless an indication that Italy still stood shoulder to shoulder with the victorious 21 Copyright © 2003 George Franklin


powers, and, although the importance of the Stresa Front can be overstated, it again showed that London regarded Italy as being inside the tent rather than outside it.43 Given this background, it is unsurprising to find the Foreign Office reporting to the CID in 1933 that Britain was ‘unlikely to go to war with Italy unless required to do so by obligations under the League of Nations’.44 The logical corollary of this, in defence planning terms, was the policy explicitly laid down in the Defence Requirement Committee’s 14th paper, its first full report. In this paper, which discussed the perceived threats, the committee stated that ‘No expenditure should be incurred on measures of defence required to provide exclusively against attack by the United States, France or Italy.’45 Italy nonetheless had a substantial offensive capability, albeit geographically limited, and, whatever the Foreign Office thought, the Service Departments might have found it prudent, even in the vaguest context, to make themselves ready for a Mediterranean conflict. Further, while it is easy, in pointing to the Abyssinian crisis, to suggest that the committee gave poor advice, a close examination shows that their thinking was, at least as far as A/S matters were concerned, perfectly coherent. The committee’s report directed the navy to ‘show a tooth’ to the Japanese but to make itself ready in the long term for a war with Germany in which France would be on Britain’s side. In following this direction, it would be ready in the short term to defend warships against Japanese submarine attack in the Far East, and would gradually prepare itself to defend merchant trade against unrestricted attack in the narrow waters of north-western Europe. Notwithstanding some of the wilder dreams of the fascist leadership, the Chief of the Italian Naval Staff, Admiral Domenico Cavagnari, seems to have accepted that his navy would never operate in strength beyond Gibraltar or Suez, so Britain’s worldwide trade would never be threatened by Italian naval action.46 In the event of a war with Italy, therefore, British merchant traffic could be diverted around the Cape, and the naval battle in the Mediterranean would see Britain making an all-out attack on Italian maritime assets while having to defend only its warships. If they had prepared, therefore, for defence against the Japanese threat, they would inherently be ready for war with Italy. The coherence of this policy was further illustrated by the fact that, after the Abyssinian crisis, the position with specific regard to Italy was not changed. Rather, clauses started to appear to the effect that the Navy needed to be ready to react to crises which might, with little notice, emerge as a result of commitments to the League of Nations. The Abyssinian crisis, therefore, was not seen as an indication that relations with Italy were likely to lead to further confrontation. It was, instead, seen as a demonstration of how a treaty commitment could lead the nation unwittingly to the brink of an unpredictable war. 22 Copyright © 2003 George Franklin

STRATEGY

In discussing the strategy which informed inter-war A/S policy, one further subject is worthy of mention—the vulnerability of France to German invasion. It will be shown later in the book that the Royal Navy’s plans with respect to a German offensive revolved around a submarine attack in the narrow waters around Great Britain and in the Atlantic approaches north and south of Ireland. A sustained mid-Atlantic attack was not expected for the simple reason that the boats, according to the Admiralty plans, would be based in Germany, or at the limit in Belgium and Holland. The capture of the Biscay ports in June 1940, and their development as U-boat bases, fundamentally altered the geography of trade defence. After the summer of 1940 Dönitz was able to put growing numbers of boats into the mid-Atlantic for extended periods, where convoys had previously been able to sail undefended, and where the water was deep enough to demand changes in tactics and equipment. The question to be addressed here, then, is why the Royal Navy did not plan for a campaign against shipping in the deep Atlantic. The simple answer is that it was instructed not to.Throughout the Foreign Office, CID and Defence Requirements Committee papers that cover reactions to the German threat there is a running theme, sometimes implicit, sometimes explicit, that in the event of a war against Germany the possibility of France falling was not to be apprehended. This was referred to in terms of army and air force planning, in Mediterranean strategy, which divided responsibility between the British and French navies, and in trade defence. The two fundamental reasons for this refusal to contemplate a solitary stand were first that it does little good to an alliance if one party is found to be planning against the collapse of the other, however practical and realistic such planning may be, and second that it was not thought possible to conduct such a war. While Britain’s inability to win such a war could never be confessed in public or official documents, private thoughts do find their way into private memoirs.We thus have General, later Lord, Ismay’s private opinion that if the Chiefs of Staff had been asked to plan for war without France they would have replied that it was not winnable.47 We also have Eden’s evidence that, even for the feared war against Italy in 1935, Britain ‘needed’ the use of French Mediterranean ports,48 and implications in other papers that French collapse would leave Britain in an untenable situation with respect to Germany.49 CONCLUSION In the early post-war years then, there was no readily identifiable submarine threat either to trade or naval units, but there was a general awareness that such a threat could easily develop. The consolidation of the capabilities developed during the war was, therefore, not driven by any particular menace, but by a general need to maintain a core skill. Similarly, there was no need to 23 Copyright © 2003 George Franklin


prepare for a specific conflict, but it was felt important to pursue the subject at an academic level and to continue scientific research. The cooling of Anglo-Japanese relations in the early 1920s provided the Admiralty with a specific threat against which to configure. The extent to which this threat was amplified by their Lordships to strengthen their hands in battles with the Treasury is not significant to this book.What is important is that planners, tacticians and designers now had a specific scenario to address. Broadly, that scenario involved the Japanese Battle Fleet and cruisers, supported by an integrated submarine force, attempting to seize total sea control in the Far East. To counter this it was necessary to prepare a battle fleet that could meet the Japanese on the high seas and, at the very least, destroy sufficient of their ships to prevent them from exercising regional sea control. Japanese submarines were expected, by both sides, to act in support of their surface units by attacking the British Fleet, while the attack on trade would be the responsibility first of cruisers and later of main fleet units. This Japanese threat remained in place throughout the late 1920s and the 1930s, and the nature of the 1941–45 naval conflict in the Pacific, although the battleship was largely replaced by the aircraft carrier, showed that expectations with respect to the Japanese submarine threat were generally sound. During the mid-1930s, however, the Japanese submarine threat to the fleet was overtaken by the growing danger from the redeveloping German U-boat arm. Analysis of German intentions was more problematic, but there was a general expectation that they would make another attempt to isolate Britain by means of a submarine attack on trade.The Home Fleet remained a valuable asset, however, especially given its offensive value against German surface raiders, and defence of heavy naval units thus remained important. From around 1933, then, the Royal Navy was required to prepare to defend both warships and merchantmen from submarine attack. Specifically, anticipating that war against Germany was only viable if France remained substantially intact as an ally, it was envisaged that the submarine attack would be largely restricted to the European continental shelf. Italy, the third main enemy when war came, was not seen by the Foreign Office as being a threat until Mussolini’s African ambitions became clear, so the Admiralty was not required to plan against the eventualities of war against Italy. By the time Mussolini declared his opposition to London, in the mid1930s, his military machine was exceeded in size and quality by both Germany and Japan, and it was generally felt that one could prepare for war against Italy by preparing for war against the other two.There was, therefore, no specific requirement to plan against Italy.


STRATEGY

NOTES 1 2

3 4 5 6 7

8 9 10 11 12 13 14

15 16

17

18 19

Stephen Roskill, Naval Policy between the Wars, Collins, London, 1968, Vol. 1, p. 92. The Hague convention of 1907 allowed submarines to attack warships or merchant ships in convoy without warning. They could also attack independent merchant ships without warning if they had committed a hostile act, such as firing on the submarine or making a distress call indicating the submarine’s position. An independent merchant ship that committed no hostile act could be stopped but the personnel in the ship had to be allowed to disembark to the boats before the submarine could sink the ship. The submarine commander also had a duty to ensure that the crew had a reasonable chance of survival. A campaign not in accordance with these rules was known as an unrestricted campaign. The 1930 London Naval Treaty, signed by Britain and Germany, confirmed that the Hague convention rules applied to submarines. PRO ADM 116/1775, Beatty memo to Bonar Law committee, dated 14 Dec. 1920. Covering letter to report, dated 21 Aug. 1919, in PRO ADM 116/1834, cited in Roskill, Naval Policy, Vol. 1, p. 278. PRO ADM 167/56, Navy Board Minute 958 of 25 Sept. 1919. Roskill, Naval Policy, Vol. 1, p. 327. E.L.Woodward and Rohan Butler, eds, DBFP 1919–1939, 1st series, vi, London, 1956, cited in Arthur Marder, Old Friends, New Enemies: The Royal Navy and the Imperial Japanese Navy, Strategic Illusions, 1936–1941, Clarendon Press, Oxford, 1981, p. 6. PRO CAB 16/109, DRC paper 20, dated 24 Feb. 1934, Foreign Office notes about situation in the Far East. Marder, Old Friends, New Enemies, p. 6. PRO CAB 5/4, CID 176C, 28 July 1922. Beatty to de Robeck, 11 Apr. 1923, enclosing copy of Admiralty letter M0421/23 of 19 Apr. 1923, de Robeck papers, cited in Roskill, Naval Policy, Vol. 1, p. 354. Roskill, Naval Policy, Vol. 1, p. 409. PRO CAB 4/21, CID 1055B. For a discussion of the planned and actual use of Japanese submarines, see Carl Boyd and Akihiko Yoshida, The Japanese Submarine Force and World War II, Airlife and Naval Institute Press, Shrewsbury, 1996. Boyd and Yoshida, Japanese Submarine Force, p. 5. Asada, Sadao, ‘The Revolt Against the Washington Treaty: The Imperial Japanese Navy and Naval Limitation, 1921–1927’, Naval War College Review, 46, 3, p. 92; cited in Boyd and Yoshida, Japanese Submarine Force, p. 6. For a discussion of the Naval Intelligence Division’s efforts against Japan, which were not great, see G.D.Franklin, ‘Blind Approach: An Investigation of Britain’s Ignorance of the Imperial Japanese Navy in December 1941’, Naval Review, Vol. 84, Nos 3, 4. PRO CAB 4/22, CID 1113-B, 1933 annual review by the Chiefs of Staff Committee, pp. 6–7. PRO CAB 116/3603, Appointment of Additional Officers to HMS Osprey, D of TD paper dated Dec. 1931.


BRITAIN’S ANTI-SUBMARINE CAPABILITY, 1919–1939 20

21

22

23 24

25 26 27 28 29 30 31 32

33 34 35 36 37 38 39 40

For a discussion of Fleet tactics as applied to a Far East war, see ‘The Development of the Royal Navy’s Strategy and Tactics for a War in the Far East’, unpublished MPhil. thesis by Andrew Field, University of Leeds School of History, Sept. 1999. PRO ADM 16/109, CID 1147-B, the First Report of the Defence Requirements Committee, confusingly DRC paper 14. For conflicting interpretations, see Andrew Gordon, British Seapower and Procurement between the Wars: A Reappraisal of Rearmament, Naval Institute Press, Annapolis, MD, 1988, p. 123, and Roskill, Naval Policy, Vol. 2, p. 169. PRO CAB 4/22, CID 1113-B, 1933 annual review by the Chiefs of Staff Committee, p. 14. The Locarno Treaty, signed by Britain, Italy, France, Belgium and Germany in 1925, guaranteed Germany’s borders with France and Belgium. Although the treaty was in reality aimed at containing Germany, it would have been theoretically possible, following a French invasion of Germany, for Britain to find itself fighting alongside the Germans and Italians against France. PRO CAB 4/22, CID 1134-B, German Industrial Measures for Rearmament and for Aircraft Production, March 1934, p. 2. IvS, or Ingenieurskantoor voor Scheepsbouw, or ‘Inkevos’ as it is sometimes called, was a company set up in the Hague in 1922 to allow German engineers to study the construction of U-boats away from the prying eyes of those who were charged with upholding the conditions of Versailles. For a succinct account of German clandestine submarine building, see John Terraine, Business in Great Waters: The U-boat Wars 1916– 1945, Leo Cooper, London, 1989, pp. 168–9. Joseph A.Maiolo, The Royal Navy and Nazi Germany, 1933–1939, Macmillan, London, 1998, p. 102. Gordon, British Seapower and Procurement, p. 126. Dan Van Der Vat, Standard of Power: The Royal Navy in the Twentieth Century, Pimlico, London, 2000, p. 15. Gordon, British Seapower and Procurement, p. 271. PRO CAB 4/22, CID paper 1112-B, Foreign Office Memorandum on the Foreign Policy of HM Government, June 1933, p. 4. PRO CAB 4/22, CID paper 1113-B, Annual review by Chiefs of Staff Committee, Oct. 1933, p. 2. PRO CAB 16/109, CID 1147-B, First report of the Defence Requirements Committee, paper DRC 14, p. 9. The Stresa Front was the name given to the agreement made in 1935 between Britain, Italy and France to continue to be bound by the terms of the Locarno Treaty. The hope at the time was that this ‘front’ would act as a break on German expansion to the west, but this faith was to prove ill founded. For a modern interpretation of the background to and consequences of the AngloGerman Naval Agreement, see Maiolo, Royal Navy and Nazi Germany. PRO CAB 16/112, DRC paper 26, submitted by CNS 24 July 1935. PRO CAB 4/26, CID 1368-B, Protection of Seaborne Trade, Nov. 1937, p. 2. PRO CAB 4/26, CID 1323-B, Review of Imperial Defence by the Chiefs of Staff, May 1937, p. 7. PRO CAB 4/26, CID 1368-B, Protection of Seaborne Trade, p. 7. PRO CAB 2/7, 326th meeting of the CID, 2 June 1938. PRO CAB 4/26, CID 1318-B, Defence Against Submarine Attack, March 1937, p. 1. Ibid., p. 3.


STRATEGY 41 42 43

44 45 46 47 48 49

PRO CAB 16/112, DRC paper 33, Naval Defence Requirements, submitted by CNS in Oct. 1935. PRO CAB 4/26, CID 1368-B, Protection of Seaborne Trade, pp. 2, 16. See Robert Mallett, The Italian Navy and Fascist Expansionism, 1935–1940, Frank Cass, London, 1998, pp. 18–21, for a modern analysis of Mussolini’s motives at Stresa. A good contemporary analysis can be found in Anthony Eden, Facing the Dictators, Cassell, London, 1962. PRO CAB 4/22, CID paper 1112-B, Foreign Office Memorandum on the Foreign Policy of HM Government, p. 7. PRO CAB 16/109, CID 1147-B, being DRC 14, dated 28 Feb. 1934, p. 4. Mallett, Italian Navy. Ismay, The Memoirs of General the Lord Ismay, Lon, London, 1960. Eden, Dictators, p. 268. For example, see The Cunningham Papers, Vol. 1, 1939–1942, Navy Records Society, Aldershot, 1999, and Winston S.Churchill, The Second World War, Vol. 1, The Gathering Storm, Cassell, London, 1948.


2

Organisation

THE NAVAL STAFF In order to have any understanding of the process which led to major decisions about capability development, we need to have a sound understanding of the structure of the Naval Staff. No such discussion could be complete without a ‘wiring diagram’, and Figure 1 shows the hierarchy of responsibilities within the Staff.1 Leading the organisation was the Chief of the Naval Staff (CNS), also known as the First Sea Lord (1SL or simply ‘First’), the professional head of the navy. He was responsible, through the First Lord of the Admiralty, a politician, to the CID and the Cabinet for the running of the Royal Navy. Working for the CNS were the Assistant Chief of the Naval Staff (ACNS) and the Deputy Chief of the Naval Staff (DCNS), officers of broadly equal seniority with very different areas of responsibility. The Deputy Chief of the Naval Staff was responsible for plans and operations, and has been described as the ‘user’. The Assistant Chief of the Naval Staff, covering procurement, tactical development and some aspects of training, could be styled the ‘provider’.The Assistant Chief of the Naval Staff ’s responsibilities for training were shared with the Second Sea Lord (2SL or ‘Second’), who can be thought of as the personnel manager. While final decisions lay with these senior officers, the majority of the functions of the Staff, including analysis of proposals and submission of recommendations to the decision makers, fell to the various directors who worked for them. Generally officers of Captain’s rank, these were selected for their expertise in the business of their departments, so many posts ‘belonged’ to certain branches or specialisations. Of the directors who reported to the Assistant Chief of the Naval Staff, for instance, the Director of the Signal Division (DSD) was a specialist communicator, and the Director of Scientific Research (DSR) was a civilian scientist. Less obviously, the Director of the Tactical Division (D of TD) tended to be a torpedo specialist; the significance of this will be discussed later. Of the directors who reported 28 Copyright © 2003 George Franklin

Figure 1: Sea Lords and Sections of the Naval Staff Concerned with Anti-Submarine Matters Copyright © 2003 George Franklin


to the Deputy Chief of the Naval Staff, the only ones who are of direct concern to us are the Director of the Operations Division (DOD) and the Director of Plans (D of P). Among other roles, the Director of Plans, who tended to be a gunnery specialist, sat with his army and RAF opposite numbers on the Joint Planning Committee (JPC), which prepared reports and appreciations for the CID and the Cabinet. The Director of Plans, however, had no direct responsibility for anti-submarine development, which fell within the bailiwicks of the Director of the Tactical Division, the Director of Scientific Research and the Director of the Signal Division. Captain A/ S, whose role will be discussed in the next section, reported to the Director of the Tactical Division in matters of tactics, training and production, and was responsible to the Director of the Signal Division for scientific development. The Department of Scientific Research and Experiment, under the Director of Scientific Research, was established in 1919. It was perceived at the time that science in the navy had spread during the war into an uncoordinated and, in the worst cases, uncontrolled sprawl, and F.E.Smith, as Director, was tasked to rationalise the development of science.2 Responsible to the Third Sea Lord, but also reporting to the Assistant Chief of the Naval Staff, he was to oversee the work of Admiralty establishments and to provide the link between the Admiralty and civilian institutions.The post of Director of Scientific Research was, throughout the period, an important one in the development and production of asdic as well as in the setting to work of equipment.3 Prior to the 1921 reorganisation of the staff, an Anti-Submarine Division existed in its own right. It was proposed in 1921 that the Anti-Submarine Division, together with Mercantile Movements and Minesweeping, should become part of an expanded Trade Division,4 in order to unify all aspects of trade defence. In the event, it became part of the Tactical Division, and was cut to a staff of only one commander. To put this into perspective, this commander was one of 85 uniformed officers in the Staff, and at no time in the inter-war period was the post occupied by an anti-submarine specialist.5 His administrative support came from the ten civilian clerical and secretarial staff who were shared between the Tactical, Plans and Trade Divisions. The practice of repeatedly appointing Torpedo Officers to the posts of Director of the Tactical Division and Captain A/S meant that no gunnery officers, and thus no subsequent Directors of Plans, had deep experience in anti-submarine matters. This compartmentalisation of anti-submarine expertise within the staff was exacerbated by the tendency, superficially beneficial, to appoint ex-Captains A/S to the post of Director of the Tactical Division. From this it can be seen that there was a narrow vertical stratum of anti-submarine expertise, or at least understanding, within the Staff, which should have allowed efficient development of material, tactics and manning throughout the period under study. This book will argue that, given the 30 Copyright © 2003 George Franklin

ORGANISATION

prevailing technological constraints and strategic drive, advances in antisubmarine matters were as satisfactory as could reasonably be expected.What was not satisfactory was the integration of tactical capabilities and limitations into strategic planning and wider policy. The reasons for this failure can be shown to have lain within the structure of the Staff. Broadly, strategic policy, especially in peace, is concerned with what will be done in the future, its main building blocks being identification of a potential enemy, assessment of its capabilities and intentions, and a proper recognition of one’s own capabilities and limitations. Given these factors it is possible to come up with a series of contingency plans. All this was done, on a tri-service level, by the JPC, and in the Admiralty by the Director of Plans, himself a member of the JPC. As has already been discussed, the Director of Plans tended to be a gunnery specialist with a background in capital ships and little or no detailed understanding of anti-submarine warfare. Similarly, there was within his staff no expertise in anti-submarine matters, so their understanding of the RN’s own capabilities and limitations must have been, at best, limited.The CB (Confidential Book) 3002 and CB 1769 publications would have been their only reference source. The CB 1769 series were annually produced secret reports on exercises of particular interest or significance. They contained descriptions of the exercise plans, narratives of the involved forces, and retrospective comments from commanders. As such they are of great interest to the historian and would have been useful to those in the Staff and other organisations who needed to keep track of practices in the fleets.They do, however, only cover a very few of the exercises undertaken, so do not provide anything approaching a full record. The most useful surviving documents to come out of Portland were the CB 3002 series, entitled ‘Reports of Progress in Torpedo, Mining, AntiSubmarine and in Allied Subjects’,6 which were published every year from 1924 to 1939.These reported on, among other things, the progress made at Portland in tactical developments. In order to give results which could be analysed and compared, a series of standard exercises were devised, and criteria established to assess the success of those exercises.The exercises, and the success criteria, are discussed at length in Chapter 6. The Directors of Plans, then, appear to have relied on these two series of documents, and there is no evidence of them making a habit of going to the Tactical Division, or indeed Captain A/S, for advice or guidance. The appreciations drawn up by the JPC for the Committee for Imperial Defence do survive, as do some of the drafts which were circulated within the Naval Staff prior to publication, and it seems that in the majority of cases they were not circulated to any of those sections of the Staff which possessed expertise in anti-submarine.7 The Chiefs of Staff, the CID and, ultimately, the Cabinet were thus presented with visions of how a future trade defence campaign would be pursued, which had been prepared without input from 31 Copyright © 2003 George Franklin


the experts in the newly emerged and rapidly evolving discipline of antisubmarine warfare. It can hardly be surprising, then, that while the officers of the fleets were struggling through exercises without receiving ‘the ghost of an echo’,8 Admiral Chatfield (First Sea Lord) was writing to Churchill in 1936 that ‘Our anti-submarine methods are so efficient, not of course 100 per cent efficiency, but I do not think that 80 per cent is too high an efficiency to safely put it at’9 and Samuel Hoare, as First Lord of the Admiralty, was telling the CID in 1937 that ‘the position is very satisfactory’.10 The result of this failure was that much of government and Admiralty policy was based on flawed assumptions some of which, as will be shown later, can be laid at the door of the Portland organisation, but many of which were due to the ignorance of the planners.11 It has already been given that the anti-submarine expertise of the Naval Staff was limited to a core of officers who would frequently return to the same area, concerned primarily with procurement and tactical development, and that there were few if any in the Operations and Planning Divisions who had understanding of or experience in anti-submarine matters. From this comes the natural conclusion that those who conducted the strategic planning did so without the benefit of an appreciation of asdic’s capabilities and limitations. What is less obvious is the reason why the officers of the planning and operational divisions should have been optimistic rather than pessimistic about the performance of anti-submarine forces. For this one must look to the branch structure. All Commanding Officers of ships, the vast majority of Admirals and virtually all officers of influence in the Staff were of the executive, or seaman, branch. After about five to eight years in the service, non-submariner executive branch officers tended to specialise either in gunnery, torpedoes (which included electrics), navigation, communications or antisubmarine. Specialisation would involve a course of about one year’s duration, at the Alma Mater of the chosen branch (HMS Excellent for gunners, Vernon for torpedomen, Mercury for communicators, Osprey for anti-submarine officers, etc.).When he had completed his chosen course, the officer’s specialisation would be shown in the Navy List, he would time and again be appointed to specialist jobs and he would feel very much part of a tribe. Different branches affected small uniform variations; gunnery officers for example carried black silk handkerchiefs, supposedly so they could wipe the cordite from their faces without the soiling showing, while communicators, who as flag lieutenants held themselves to be the aristocrats of the service, carried white silk handkerchiefs and wore black silk ties. A constructive tension built up between the tribes which meant that designs, plans, strategy, etc. were generally the result of compromises between the requirements and desires of different branches. The sketch estimates for a new destroyer, for instance, would carry the gunnery officers’ opinion that the ship would be useless without large-calibre primary armament and effectively directed high32 Copyright © 2003 George Franklin

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angle secondary armament, while the torpedoman would point to the benefit of having large numbers of torpedo tubes and the communicator would insist that both these should be compromised to allow for an effective communications outfit.The resulting destroyer would be a sensible all-round compromise. Into this scene of established and senior branches came the new, junior and slightly quirky anti-submarine expert. For the first few years no qualified antisubmarine officer was senior enough to be part of the Staff decision process, so their corner was fought by torpedo specialists, but as time progressed qualified anti-submarine men entered the debates. In the normal course of things the anti-submarine man would have lobbied for greater and greater provision for his discipline, but what actually happened was that, having as they did to fight the more senior branches for influence, A/S specialists tended to emphasise the effectiveness of their equipment. As Backhouse wrote in 1931, ‘nothing discredits the value of a new service so much as failure in the Fleet, or if not actual failure, poor results’,12 so the A/ S specialists will have been loth to tell anyone that their equipment had shortcomings.The gunnery officers, who for no better reason than tradition largely owned the Plans Division, were keen throughout the period to centre the navy around big gun battleships, and were very ready to leap on any support this cause was given.When a Portland report told them, for instance, that a destroyer on the quarters on a convoy would ‘be in a position to obtain contact at once with a submarine attacking a convoy’,13 they hardly questioned it but instead jumped to the conclusion that the submarine menace was dealt with, so they could get on with developing a battleshipand cruiser-based fleet. The subject of anti-submarine, therefore, became an area where the usually productive system of constructive tension broke down and the two naturally opposing sides of the debate came up with the same argument, that antisubmarine methods were more effective than was in fact the case. In this way a spiral of self-deception developed which finally led wartime planners to send out groups of ships to hunt for dived submarines, a role for which they were entirely unequipped. There were other occasions when officers who were in full possession of the facts may have, for political reasons, overstated the efficiency of the capability. A letter from Chatfield to Churchill, written about the Italian submarine threat during the Abyssinian crisis, stated that the Italians had far more [submarines], for instance, than Germany will have in the Anglo-German Naval treaty…[but]…the five [destroyer] flotillas that we have been keeping in the Med will be able to crush the Italian submarine forces and drive them into port and the experience those submarines will have will be so alarming to them that we believe it will demoralise them.14 33 Copyright © 2003 George Franklin


Churchill replied that I am delighted at all that you tell me about your increasing mastery of the submarine, that poisonous curse upon British sea power. I believe myself that the day will come when the air menace to the Royal Navy will be equally mastered.15 Chatfield was talking about defence of warships in the Mediterranean, all merchant ships having been diverted around the Cape, in which case his statement, while optimistic, was not entirely outrageous, and was consistent with the results being obtained at Portland and in fleet exercises. This subtlety, however, seems to have been lost on Churchill, who took it as a statement of general confidence in A/S measures. Chatfield could, undoubtedly, have explained the case more fully to Churchill, and for an explanation of his disingenuous wording one must look closely at his relationship with Churchill and the motives which, at the time, were uppermost in his mind. To take the former, Churchill, although out of office, was not without influence, and was fast becoming the leading advocate of large-scale rearmament. It was, therefore, in Chatfield’s interest to keep him informed of all the Admiralty’s arguments for increasing spending. Taking this in isolation, it would seem odd to find the First Sea Lord hinting that all was well in the world of anti-submarine warfare if such was clearly not the case. At the time, however, Chatfield was fighting a hard battle to get approval for the construction of the full class of what would become the King George V battleships. A supplementary estimate had been approved in April 1936, the month before the above correspondence, which allowed for the construction of the first two of the class, but further building programmes were far from guaranteed.16 In these circumstances it would hardly be surprising to find that Chatfield had deliberately fed his parliamentary ally with an idea that the submarine menace had been mastered, and that the main threat to trade came from surface raiders. Churchill, given his known ambition, and his desire to return from the political wilderness, would at the time have made a particularly useful conduit into parliamentary debate. Such manipulation, seen in the perspective of the time when the Admiralty was still kick-starting the engines of rearmament, appears to have been intelligent, even cunning, and in retrospect successful.When one considers, however, that it probably contributed to Churchill’s wartime conviction that submarines could be hunted and killed in the open ocean, the unpredictable and potentially dangerous results of such Machiavellian pleading become evident.


ORGANISATION

THE ANTI-SUBMARINE (OFFICERS’) BRANCH The announcement of an intention to establish a specialist anti-submarine branch for officers came in 1922 with the publication of AFO (Admiralty Fleet Order) 1815. The first qualifying course, completed by five officers, took place at Portland in March 1923. This course lasted one and a half academic terms and included instruction in mathematics, physics, applied electricity and mechanics as well as the more practical maintenance and operation of anti-submarine equipment. The course was soon extended to last two full terms. The need for these officers was supported by a paper from the Second Sea Lord’s Office, which laid down the requirement for A/ S specialists as shown in Table 1. Table 1: Bearing and Requirement of A/S Specialist Officers, 1922

Source: PRO ADM 1/8731/212, Development of the Anti Submarine Service, minute by NA to 2SL, 27 Oct. 1922.

The stated policy in 1924 was to maintain a nucleus of trained anti-submarine specialists afloat, in shore staffs and at Portland. Captain A/S recommended to the Director of the Tactical Division that Lieutenants A/S shall in their junior time at Portland be given as much experience as possible in their specialised duties—both on the Instructional staff and in the Flotilla—to ensure that capable and experienced officers will be forthcoming to fill the more important appointments.17 He saw these important appointments as being the senior positions at Portland and on the staffs of various embarked senior officers. He also predicted that a requirement would arise for A/S specialists on the staffs of Rear-Admiral Submarines at Fort Blockhouse, Portsmouth and the Fleet Commanders-inChief, though these billets were not yet filled. Non-specialist officers who showed an aptitude for A/S would be encouraged to take the course, and if this failed they should, if possible, be kept in A/S vessels as long as possible.18 One can see in all these notes a determination to establish the branch on a sound basis, so that it might thrive and flower in later years. There were, 35 Copyright © 2003 George Franklin


however, divergences of opinion as to the value of this aim, the Commanderin-Chief Portsmouth in particular believing that the A/S branch was no more than a temporary measure. At the time, specialist electrical officers were being trained ready to take responsibility for electrical equipment from the torpedo officers who had, since the first introduction of electric underwater weapons, overseen all matters electric.The C in C Portsmouth seems to have thought that, when they were disbursed of their electrical responsibilities, the torpedo officers would ‘take over all under water fighting appliances’.Those who were involved in the development of the A/S branch and, vitally, the Second Sea Lord, fortunately continued to regard the branch as a permanent fixture, and C in C Portsmouth’s ideas died an early death. Indeed, Captain A/S’s enthusiasm for the new branch was such that he wanted to train more officers than there were jobs, in order to provide for further expansion.The Second Sea Lord, notwithstanding the glut of junior officers from which the navy was suffering at the time, did not feel able to justify training officers in anticipation of a future requirement, and demurred. There was a shortfall, in late 1924, of officers presenting themselves for specialist A/S training, so a further AFO, 150 of 1924, was published encouraging volunteers. This appears to have been successful, and in the following year three new billets at Portland were filled by trained officers, as well as one on the staff of Rear-Admiral Submarines, and one in the experimental department of the Signal School. By early 1927 the throughput at Portland was such that a bid for two more stewards and an extra cook for the mess was thought to be justified, and a further seven engineering and trade ratings were required to support the experimental and production parts of the establishment.The branch continued to grow, with LieutenantCommander N.J.William Powlett joining HMS Warspite in the Mediterranean Fleet as the first Commander-in-Chief ’s A/S officer. Seven months later Lieutenant-Commander F.J.Walker went to HMS Revenge and became William Powlett’s opposite number in the Atlantic Fleet. Finally, in the late 1930s, the Rear-Admiral Destroyers in each of the two main fleets had an anti-submarine specialist added to their staffs. Table 2: Training of A/S Officers at Portland, 1935–38

Source: PRO ADM 186/519, 527, 536, 547, Portland Annual Reports 1935–38.


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The Director of Scientific Research commented in 1924 that, as asdic was developing fast and the ten-year rule was still in place, it was likely that the equipment fitted to ships in 1925 would become obsolete before the outbreak of war. It was therefore, he argued, pointless to train large numbers of men to use equipment which would never be used in action.19 It is unknown if this opinion held wide currency, but it does have a certain logic, and may have contributed to the dramatic expansion in the branch following the removal of the ten-year rule. Another small assault on the branch came in 1928 when it was pointed out that only 50 per cent of anti-submarine specialists were serving in seagoing appointments, as against 70 per cent for gunnery and torpedo specialists.20 This apparent inefficiency was successfully defended on the grounds that the ratio was likely to change as more asdic sets were fitted at sea. The destroyer building programme planned for 1932, which was the first after the decision had been taken to fit all new destroyers with asdic, was expected to stretch Portland’s training facilities beyond capacity, and in August 1932 the Director of the Signal Division pointed out that more instructional staff were required at the school. In the event, their Lordships granted funding for an extra Lieutenant-Commander, an extra Lieutenant, one schoolmaster and a Senior Rate Instructor. This was followed in 1933 and 1934 by a steady increase in the support establishment, including clerical staff, a drafting officer and even more instructors.21 Throughout the period, however, it was difficult to recruit young officers into the A/S branch. First among the reasons was the fact that A/S, unlike the older trades such as gunnery and signals, was not a compulsory part of a young officer’s initial training. He could thus quite easily reach the seniority at which he would have to choose his specialisation without ever having had anything to do with A/S. Indeed, the Admiralty Fleet Order which set out the training to be given to young officers mentioned ‘Asdic screening’ only as part of the training to be undertaken ‘on a station where destroyer training can be arranged’.22 A second factor may have been the small size of the branch itself. In 1935 it was reported that 88 per cent of RN lieutenants specialised in one branch or another, but that only 11 of 1,029 lieutenants and 16 of 972 lieutenant-commanders had specialised in A/S. One can thus see that the branch had failed to achieve that critical mass which is required for natural further growth.23 There is no doubt that the anti-submarine branch was an unfashionable section of the navy, as is backed up by the verbal evidence of a number of officers of the period, contemporary literature, and the difficulties encountered in recruiting officers into the branch.The reasons for this lack of appeal were many and various, and among the most obvious were the tendency for frequent postings to the relatively cut-off and austere establishment at Portland, notwithstanding what one Captain A/S described 37 Copyright © 2003 George Franklin


as the peninsula’s ‘bracing and exhilarating climate’. Other factors were the limited scope of seagoing appointments, the widely held perception that anti-submarine was a subject for rather odd technical specialists, and the sometimes pedestrian nature of the ships used for anti-submarine work. In the latter regard it should be remembered that repeated appointments to one of the hotchpotch of ancient ships that made up 1 A/S were inevitable for an anti-submarine specialist.The Admiralty’s attitude to the requirements of anti-submarine ships is nicely illuminated in a 1928 paper on destroyer policy.24 The conclusion of this paper was that one should build destroyers with the intention that they be used in their conventional roles with the fleets for the first half of their lives.When they became too old and slow for such fleetwork they would be handed over to ‘subsidiary services’, which included anti-submarine protection of merchant traffic.This can hardly have been a great incentive for budding young officers to specialise in antisubmarine duties. Having said all of this, there were of course some fine and very dedicated men serving as anti-submarine specialists, not least among whom was Captain Walker, whose wartime success was based as much on experience gained between the wars as on his leadership or inventiveness. One finds an emphasis throughout the period on the specialist nature of A/S operations, and the high level of teamwork required between a ship’s bridge and its asdic control room as well as between the bridges of different ships. It was, however, felt that given some initial training and enough practice the majority of executive branch officers would be able to master the tactical employment of ships in the A/S role. The A/S specialists, therefore, would only be required to provide expert guidance, to train the officers who were serving in A/S ships and to supply the technical understanding of the equipment which non-specialists would lack. It is instructive to study the development of the branch between the 1925 rationalisation at Portland and the outbreak of hostilities. The appointing histories of all individual officers within the branch have been traced, and Figure 2 shows their employment by categories. Those appointments shown as ‘Fleet’ jobs include all postings to surface ships other than ships of 1 A/S, which has been placed in a category of its own as it was an experimental and trials unit rather than a true fighting formation. The fleet appointments were made up of anti-submarine specialists embarked in each of the major fleet flagships as ‘Fleet A/S Officers’, those embarked in the leaders of all asdic-fitted destroyer flotillas, those embarked in asdicfitted cruisers, and those in private ships of the asdic-fitted destroyer flotillas. The last category were a great rarity in the early years, but in the late 1930s it became more common to find anti-submarine specialists in destroyers other than those of flotilla commanders. Brief examination of the graph shows that Portland was well developed as early as 1925, as was 1 A/S.When the training and trials organisations had thus been established, A/S specialists 38 Copyright © 2003 George Franklin

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started to go to fleet appointments, which grew in number to roughly full establishment in 1928. The next advance in fleet numbers came with the destroyer building programmes of the early 1930s, and, apart from shortfalls in recruitment in 1935 and 1936, an impressive expansion was achieved between 1932 and the outbreak of war.

Figure 2: Employment of Specialist A/S Officers, and Total Personnel Strength of the Navy

The introduction of the submarine anti-submarine specialist in 1927, a man who unlike most submariners would spend his career switching between submarines and general service, must have been a most useful development. 39 Copyright © 2003 George Franklin


When serving in submarine appointments he could advise the submariners on surface ship tactics, as well as on the use of asdic for submarine-versussubmarine engagements, and when he returned to Portland or the fleets he was ideally suited to counter the latest submarine tactics. The submarine appointments were on the staff of Rear-Admiral Submarines at Fort Blockhouse and in each of the flotilla depot ships. Those in the flotillas are noted in the Navy List as being carried ‘for service in submarines’, so presumably spent at least some of their time witnessing the ‘other end’ of anti-submarine exercises. There is evidence of a flow of information and ideas between HMS Osprey and the submarine service, notably in a 1924 paper which mentions the good relationship between the anti-submarine school and the sixth submarine flotilla.25 Vice-Admiral Sir Ian McGeoch, however, a pre-war submariner who served in the first submarine flotilla in the Mediterranean, has no memory of there having been any anti-submarine specialists attached to the flotilla, despite the Navy List showing the post as having been filled throughout the period. The names of the officers shown in the Navy List were familiar to Admiral McGeoch, but he describes their influence as having been minimal. He does remember the main line of communication between submariners and surface ship officers as having been through submarine COs and flotilla commander to the destroyer flotilla commander.26 Roskill, using the evidence of Admiral Crombie, who was neither a submariner nor an A/S specialist, contends that the submariners operated as a private navy and had no input into the development of A/S tactics. The very existence of submarine A/S officers, whose appointments moved them between submarines, surface ships and Portland, must cast some doubt on this contention.27 The great majority of destroyers which did not carry qualified antisubmarine specialists instead had an officer, usually the junior sub-lieutenant, appointed as the asdic control officer: by all accounts a thankless and unpopular task. These officers generally completed a 15-day course at Portland while the Commanding Officers and Executive Officers of asdicfitted surface ships spent ten days under instruction.28 Both of these courses were divided in a rough 2:1:2 ratio between time spent in classrooms, time spent in shore-based teachers and time spent training at sea.29 Attendance on the short course was evidently not universal for asdic control officers; Sub-Lieutenant (later Captain) P.J.Cardale wrote in his memoirs that he joined HMS Escort in August 1939 as anti-submarine officer but ‘I knew very little indeed about Asdics and anti-submarine work, as I had not done a course in this’.30 During the ship’s subsequent Portland work-up, though, he did spend ten days in the shore-based attack teacher. In general, then, asdic control officers and COs received sufficient training to be able to oversee the operation of the equipment, and to execute standard tactics. There were of course exceptions. Lieutenant-Commander A.Layard, CO 40 Copyright © 2003 George Franklin

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of Walpole, implicated himself in his own diary after a 1933 exercise: ‘It was a desperate failure as we never got the ghost of an echo. I just don’t understand this pinging business.’31 Lieutenant-Commander, later ViceAdmiral Sir, Alastair Ewing was first lieutenant of Imogen when war broke out and soon found himself getting frustrated with the CO of a senior ship who had detached a single destroyer to prosecute a submarine that had been reported by an aircraft: Why in god’s [sic] name he didn’t take all of us to search I cannot understand…sending one destroyer to find a submarine after half an hour is fantastic. However he is in charge—passed over [for promotion] three years ago. He is obviously out of touch with things.32 Interestingly, the following day the C in C signalled to the CO in question that ‘When report [sic] of a U-boat is definite your whole force should be sent and remain until she is destroyed.’33 These do, however, seem to have been exceptions rather than the rule. In summary, a branch of specialist A/S officers was instituted in 1922 in recognition of the growing tactical and technical demands being posed by the asdic apparatus, and the branch expanded from its embryonic base to reach full established peacetime strength in 1928 to 1929. Removal of the ten-year rule in 193334 then increased the demand for specialists as more asdic-fitted destroyers were planned and built. The Portland establishment expanded during the years 1932 to 1934 in order to cope with the increased training load, and then stayed reasonably static, with the greatest increase being in the main fleet flotillas, as one would expect. By the outbreak of war there were trained and experienced officers in critical posts throughout the navy who were in a position to provide expert advice to seagoing commanders.There was, however, only one specialist in the Naval Staff, and none at all in the operational shore staffs. THE SUBMARINE DETECTOR (RATINGS’) BRANCH The equivalent ratings’ organisation was known as the submarine detector branch, and the first such ratings appear to have qualified in 1920.An initially qualified rating would become a Submarine Detector 2nd Class, or S/D 2nd Cl. As such he would qualify for supplementary pay and would be able to operate asdic equipment. He could subsequently qualify as an S/D 1st Cl, which enhanced his understanding of asdic operating procedures and qualified him to maintain the equipment, thereby meriting a further pay increase.The most senior SD ratings were Submarine Detector Instructors, or S/D Is, who occupied shore-based instructional posts and were at least Petty Officers. It should be noted here that SD qualifications did not constitute substantive rates, but were additional to the substantive rates of Ordinary,Able or Leading 41 Copyright © 2003 George Franklin


Seaman etc. Confusingly, while in surface ships the SD ratings were drawn from the seamen, in submarines it was the communications, or W/T (wireless telegraphy), rates who were trained as SDs. The non-substantive nature of the qualification meant, in the early and mid-1920s, that ratings were in many ways disadvantaged by qualifying. As with officers, their shore time would be spent at Portland, and much of their sea time would be spent in old ships allocated to secondary duties. More fundamentally, though, SD training did not qualify ratings for advancement to Petty Officer, and they thus had to train either as gunners or torpedomen as well as SDs. Further, SD ratings could not qualify as Boatswains, so could not advance to Warrant Officer.35 These shortcomings were overcome in1928, Admiralty Fleet Order 2090 providing for the establishment of the rate of SD Boatswain, and allowing for advancement to Petty Officer or Chief Petty Officer without the need to qualify as Seaman Torpedoman or Seaman Gunner.This AFO also formally recognised the branch as being separate from the torpedo branch, and in recognition of this granted the award of a branch badge.The branch structure remained largely unchanged until wartime, with the exception of the 1935 redesignation of S/D 2nd Cl as SD and S/D 1st Cl as Higher Submarine Detector (HSD). Operating the equipment at sea took a degree of concentration and it was reckoned that effectiveness fell off rapidly after an hour, so the usual procedure was for the operators to get 30 minutes of rest after an hour on the set. To function properly the set needed two operators, so there were generally three SD ratings on each watch, allowing the 60 minutes on and 30 minutes off to be maintained throughout the period of the watch. The ship’s company was divided into two watches, so a total of six qualified ratings were required for each asdic-fitted ship.The aim was for there to be three S/D 2nd Cl and three S/D 1st Cl (later SDs and HSDs). Unfortunately, difficulties in persuading ratings to specialise meant that in the mid-1930s there was not enough slack in the drafting system to allow SDs to be released for the HSD qualifying course, and this necessarily exacerbated the position as advancement became slower than in the ‘rival’ gunnery and torpedo branches.36 The problem does, however, appear to have been resolved, and by 1938 the shortage was over (see Table 3), and it was anticipated that the target of 1,069 SD ratings by the end of March 1939 would be achieved.37 Selection for training was not rigorous, a Tactical Division memorandum in 1938 noting that ‘any intelligent man with good hearing can be trained as an SD rating, but non liability to seasickness is a desirable attribute’.38 A form of self-selection did, however, develop in that the least suitable ratings found themselves being returned to their ships having failed the qualifying course. The training of SD ratings took place in two phases, both of which were 42 Copyright © 2003 George Franklin

ORGANISATION Table 3: Training of SD Ratings at Portland, 1929–38

Source: PRO ADM 186/519, 527, 536, 547, Portland Annual Reports 1935–38; PRO ADM 116/3603, Appointment of Additional Officers to HMS Portland, DSD minute dated 22 Jan. 1932; PRO ADM 1/12140, A/S Policy, Appendix D, ‘Training’.

based at Portland. In the first phase, which was spent in the classroom, they learnt about the operation and maintenance of the asdic equipment, as well as doing some basic work on indicator loops. Once familiar with the technical aspects of the gear, they went on to study its operation, and conducted exercises in the land-based simulators, known as ‘attack’ and ‘procedure’ trainers. Once the staff were happy that the ratings had mastered the principles, they went to sea to practise in the very much more demanding conditions of a real ship. The ships of 1 A/S were used, and reading their logs one finds weeks upon weeks of repetitive training exercises. Every weekday, the ships would put to sea at around eight o’clock in the morning to conduct A/S practices in the waters around the Portland peninsula, before returning home mid- to late afternoon. Various attempts were made to find a replacement for real submarines in the seagoing phase, but none were successful. Among these was the use of surface ships as targets instead of submarines, but it was found that this did not work as the return given by the hull of a surface ship was, due to its reduced draught, much weaker than that given by a submerged submarine. One of the fundamental problems surrounding the submarine detector branch was the requirement to expand it in wartime. As will be discussed in Chapter 5, the Admiralty’s policy between the wars was to produce designs for cheap and simple anti-submarine vessels which could be mass-produced in wartime.This meant that, in theory, plenty of ships would soon be available to counter a submarine offensive. In most respects these ships would be simple enough to be taken to sea and maintained by relatively inexperienced men with perhaps some civilian seagoing experience and the minimum of naval training. The asdic equipment, however, was highly technical, and operators required a great deal of practice before they could develop a proper feel for the device. Such men, clearly, could not be recruited in a hurry if their ships were to be fully effective. This problem was exacerbated by the youth of the branch.Whereas the older branches could call on retired ratings, or those who had left the service prior to retirement, to provide a ready pool of expertise in wartime, neither the asdic equipment nor the SD branch 43 Copyright © 2003 George Franklin


had been in existence long enough to allow such a fund of knowledge to develop. One therefore finds the Director of the Tactical Division noting in 1938 that the construction of ten ‘Fast Escorts’ in 1939 would leave the navy short of SD ratings.39 Some effort was made to recruit RNR ratings to the SD branch, and training courses were held at Portland aimed specifically at RNR SD ratings. SD(RNR) courses in 1938 were of 14 days’ duration, and HSDs of the reserve service received 19 days’ training.When one compares these figures to the 39 and 67 days available to regular servicemen for the same qualification, one begins to understand the limitations of the reservists. This manning problem also applied to the trawlers that would be taken up in an emergency, but in this case the solution was initially found to be in the ‘Patrol Service’ scheme.This allowed for fishermen to be trained during peacetime in the operation and maintenance of asdic equipment, and the skippers to be taught the basics of A/S tactics.To this end the Patrol Service ratings were, from 1933, sent to Portland to receive asdic training ashore and in trawlers.40 In an emergency a number of trawlers would be requisitioned and fitted with asdic, and crews who were familiar both with the vessels themselves and the new equipment would be available to man them. It would not necessarily be possible to match the men of the reserve to their old boats, but this was not considered to be a fundamental drawback. A conference, attended among others by three previous Captains A/S, was held in 1934 to discuss this scheme.41 A number of points were raised which generally indicated that all was not well with the Patrol Service. First, it was pointed out that at least some of the six sea days of the nine-day course for reserve SD rates were usually lost to weather, so reducing the effectiveness of the training. It was also observed that trawler skippers were by their very nature individualists, so were not good at working in the teams of ships that were so vital to A/S operations.This, it was felt, could be overcome by firm action on the part of the group commanders, who would be commissioned officers. The most damning observations, however, concerned the men themselves, who were described in the following terms: Unlike the skippers they are not usually trawlermen, but are more often line fishermen or boatmen, they are dull witted, resent having to use their brains, and often have to be instructed in the rudiments of the compass. After 14 days of training not more than 1 in 12 is of any use as an operator, and in war they would probably be of no use at all. Following this meeting the possibility of using RNVR ratings for trawler duties was discussed, but the Admiral Commanding Reserves went on 44 Copyright © 2003 George Franklin

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record as saying, quite reasonably, that as far as possible trawlers should be manned by trawlermen and that RNVR ratings were unsuitable for such service. Evidently feeling that the situation needed to be addressed, the Director of Plans wrote to the Assistant Chief of the Naval Staff explaining the situation and suggesting that ‘A decision of a member of the board might be advisable before we proceed further.’42 The result appears to have been the replacement of the Patrol Service with a ‘Special Trawler Reserve’ which would offer greater incentives but would be more selective about recruits, only accepting trawlermen. When the Special Trawler Reserve was established, probably in 1937, the men were offered a higher embarkation gratuity than had been the case for the Patrol Service, and it was reported in early 1938 that in nine months the new service had attracted more recruits than had the old in 18 months. This may in part have been due to the establishment of a network of Lieutenant-Commanders RNR as recruiting agents. It was stated in 1936 that one of these had been established in Hull, and it was planned to appoint others in Grimsby, Fleetwood and Milford Haven.43 The men of the Special Trawler Reserve were offered the opportunity to qualify both as SD ratings, which meant the successful completion of a three-week course, and as HSDs.They were offered ‘a considerable increase in embarkation gratuity’ if they qualified,44 and in 1937 it was reported that, of the 111 volunteers trained at Portland in that year, a satisfactory 78 had qualified as SDs.45 By 1938 these figures had risen to 135 men in the service, of whom 112 were qualified as SDs.There were, however, no HSD qualified ratings in the Special Trawler Reserve by this time, and, given that the Admiralty envisaged the requisitioning of 200 trawlers, each one of which would require two asdic operators, these figures still fell well short of the requirement. The Admiral Commanding Reserves made the point in late 1938 that the 100 trawlers to be taken up in the first stages of a war would require 450 trawler reserve SD ratings to man their asdic equipment. Trawler asdic, being less complex than versions fitted to warships, could be operated by one trained man and one who was untrained. Further, it was only thought necessary to provide manning to operate a trawler asdic for a maximum of 12 hours per day. The policy at the time was thus for each trawler to have one SD rating and a second who would be either SD or HSD qualified. From this it is unclear how the figure of 450 ratings for 100 trawlers was derived, but, given the plan to call up a second 100 trawlers should the emergency develop, it seems probable that Admiral Commanding Reserves was planning ahead for the worst. This is also consistent with the Director of the Planning Division’s 1937 proposal to increase the establishment of the reserve from 200 to 300 crews, around a half of which would have been used for A/S duties, the remainder being dedicated to minesweeping.46 There was at the time no shortage of volunteers, but the lack of training 45 Copyright © 2003 George Franklin


facilities at Portland was causing a bottleneck.The board therefore decided in January 1939 to bring forward three trawlers from the reserve to supplement the training vessels already at Portland.This allowed 14 skippers and four second hands to be trained every two weeks, and 24 ratings to be trained every three weeks.47 Before 1937 the procedure for wartime call-up of Patrol Service, or Special Trawler Reserve, ratings was for them to report to one of the eight mobilising officers, who were spread around the major fishing ports. These mobilising officers, who had a hand in the identification of suitable craft for take-up, would then allocate the crews to locally requisitioned boats. The system of mobilising officers was reformed in 1937, however, with their replacement by requisitioning officers, and in the same reform it was decided that all Special Trawler Reserve ratings would go to Lowestoft on call-up for a short period of refresher training, after which they would move to yards around the country to pick up boats as they emerged from their wartime conversions. THE SHORE ESTABLISHMENTS In the immediate post-war years there were a number of fundamental reorganisations of the Admiralty scientific organisation which, despite rearguard actions from scientists and naval officers, found itself being—to employ a modern euphemism—extensively rationalised. While productive work did continue throughout this period of flux, there is little to be gained from a detailed description of the changes undergone. Our detailed study of the organisation will thus start in 1925, by which time the structure that would serve until 1939 had been largely established. During the First World War, HMS Sarepta at Portland became the Royal Navy’s centre of anti-submarine activities, although experiments, trials and development work were also undertaken at outstations throughout the country.The general reduction in defence spending following the armistice left the majority of the outstations either closed down or allocated to other work. By 1924 the Admiralty Research Laboratory (ARL) at Teddington, under the direction of the Director of Scientific Research, was carrying out fundamental research into underwater sound. The Wireless Telegraphy Department of the Signal School, which was located in the RN Barracks at Portsmouth, was primarily tasked with research into, not surprisingly, the rapidly advancing field of wireless communications. This meant that the Signal School undertook some very advanced research into amplifier and valve technology.The circuitry required to convert a received radio frequency signal to an audible form was very similar to that required to convert the signal from an asdic transducer, and for this reason a good deal of the early research into asdic had taken place at the Signal School. W.F.Rawlinson and, later, N.Shuttleworth led a highly productive team of civilian scientists 46 Copyright © 2003 George Franklin

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in this asdic section, and under their direction a number of successful sets were produced.They were supported by a small and diverse flotilla of trials ships, but in 1927 much of their development responsibility was transferred to Portland. Meanwhile, the Torpedo and Mining establishment at HMS Vernon, also in Portsmouth, was working on hydrophone and magnetic indicator loop development. Hackmann describes the work of the HMS Vernon establishment as being Research carried out [that] did not contribute to the progress of asdics, nor to the fundamental knowledge of underwater sound; the establishment’s main task was to develop existing instruments, and this was carried out efficiently, though this work was also transferred to Portland in 1927.48 The asdic-fitted ‘R’ type destroyers and ‘P’ type patrol boats of 1 A/S, all of which were of wartime construction, were based at Portland.49 Initially, Captain A/S was embarked in HMS Gibraltar, and in 1924 he moved to HMS Heather.When the A/S school was commissioned as a separate entity, and given the name HMS Osprey later that year, he appears to have moved ashore and relinquished direct command of the flotilla.50 When, in 1932, it had been decided that a number of new A/S vessels should be built, it was proposed that 1 A/S should be made up of four coastal sloops, one convoy sloop and four old destroyers.51 Although the ships did not come under his direct command, they spent much of their time working in support of the A/S school. The turnaround in the fortunes of the Portland establishment can be traced to a paper written by Captain S.D.Tillard, Captain A/S, in November 1924.This paper argued that HMS Vernon’s and the Signal School’s activities should move to a greatly expanded establishment at Portland, where Captain A/S would preside over a unified and much more efficient anti-submarine organisation.While much of the paper made good sense, and was generally compelling in its arguments, Tillard does occasionally seem to have got carried away into an almost spiritualist rapture: The Scientific staff will consist of comparatively young and rising scientists in close association and co-operation with their contemporary specialist Naval colleagues, and consequently mutually benefiting one another, acting complementarily and co-ordinatedly.52 He went on to gloss over Portland’s vulnerability to air attack, but set great store by the ‘bracing air and exhilarating climate which would be conducive to intensive brain work’. The Rear-Admiral Commanding Submarines, meanwhile, was staking his own claim, arguing that it would make far more sense to unify the anti-submarine effort under his command at Fort Blockhouse in Portsmouth. 47 Copyright © 2003 George Franklin


In reaction to these two papers, the Naval Staff appointed Rear-Admiral Napier to produce a report on the future of anti-submarine development in the Royal Navy. Napier was to head a committee which included representatives, at Commander level, of HMS Vernon, the Signal School, Captain A/S, the Director of Scientific Research, the Director of Dockyards and the Secretary to the Admiralty.53 The committee was to report on three proposals: full integration at Portland, unification in the Portsmouth area, and a compromise involving administrative unification under Captain A/S with a limited actual movement of facilities to Portland. The first scheme, with a projected capital cost of £45,000 to £50,000, was judged to be prohibitively expensive and the Blockhouse scheme was thought impracticable because of the distances it would be necessary to steam to get from Portsmouth to deep water exercise areas. Almost inevitably, the compromise scheme was selected. The Directors of Torpedoes and Mining, Tactics, Signals and Scientific Research met to discuss the findings of the Napier committee, which were approved and duly endorsed by the Assistant Chief of the Naval Staff, who held responsibility for training and tactical development. The transformation was gradual, but by 5 April 1927 unification at Portland was deemed to be nominally complete, at a capital cost of £27,000. Captain A/S now had unified administrative responsibility for all anti-submarine-related matters but, while some experimental activity had moved from the signal and mining schools, much of it still took place away from Portland, notably at the Admiralty Research Laboratory, Teddington. He answered to the Director of the Tactical Division for tactical, training and production matters, and to the Director of the Signal Division for experimental affairs, though the Director of Scientific Research also, clearly, had an interest in development. Within six months it was discovered that the original buildings at Portland were uneconomical to maintain, and a further £40,000 was requested for reconstruction. After once again considering the possibility of moving the school away from Portland, the Admiralty decided in March 1928 that it was to stay in the existing accommodation, though no money was allocated for refurbishment. In what was becoming a familiar refrain throughout a cash-strapped navy, Captain A/S was told that ‘the inconvenience entailed must be accepted’. A year later, however, £50,000 was voted for office and accommodation improvements, and Captain A/S could relax in the knowledge that the inertia of capital expenditure had secured the future of his establishment. Indeed, by 1928 progress was such that the Director of the Tactical Division, who as a fully informed member of the A/S organisation would not have been one of the Naval Staff ’s blind optimists, was asking the Board of the Admiralty to express its appreciation of the work at Portland:


ORGANISATION

The results of anti-submarine work at Portland are becoming progressively satisfactory, and a marked improvement is noticeable in the successful retention of contact with submarines over long periods and under weather conditions which at one time caused, almost invariably, loss of contact. This steady improvement is attributable to patient and systematic training, and to steady improvement in tactics rather than to any marked improvement in the material used, and is therefore considered to reflect great credit on all ranks and ratings concerned in the A/S establishment, and in the co-operating submarine flotilla.54 The Portland establishment, often referred to as the Anti-Submarine School, comprised three distinct sections: instructional, tactical development and experimental. In terms of uniformed complement, the largest was that devoted to instructional duties.The tactical section, which comprised two Lieutenant or Lieutenant-Commander A/S specialists, was charged with duties specifically laid down in the establishment orders: 1. 2. 3. 4. 5.

Conduct, and analyse all tactical exercises carried out at the direction of the school, and write reports thereon. Initiate tactical developments and investigate tactical problems. Assist in the recording of special exercises. Scrutinise reports from 1 A/S and fleet flotillas. Prepare tactical manuals, quarterly reports and the CB 3002 series.55

It will thus be seen that their role was central to the employment of newly developed equipment, and it is instructive to reflect on the later importance of the part played by these two junior officers, accommodated as they were in a dilapidated office perched on the side of the Portland peninsula. Unfortunately, the Navy List shows officers as having been appointed to Portland without specifying their employment, so we are unable to identify the individuals who occupied the posts. The requirement to train officers, operators, instructors and entire ships’ teams at Portland, combined with the expense involved in using ships for training, drove the effort to build a number of simulators. The first was the attack teacher which, installed in 1925 for officers to learn how to handle a ship during an attack, also allowed an operator to practise on his equipment. The ship and submarine were represented by spots of light projected through a glass table on to a piece of paper, and the beam of the asdic set was represented by a light beam emanating from the ship. When the beam hit the submarine the trainee operator, who was in a mock-up of a ship’s asdic hut, heard an echo, which he reported to the control officer. The control officer then steered his ship to conduct the engagement. Commanding officers could also be trained on this equipment, though they do not always appear to have enjoyed the experience!56 49 Copyright © 2003 George Franklin


The attack teacher at Portland appears to have been a great success, and similar facilities were installed during the late 1930s in other home dockyards and on foreign stations. Portland was the only place where individual training was undertaken, so these other simulators were clearly used to train ships’ teams, and we have the evidence of Lieutenant-Commander Layard’s diaries that as Commanding Officer of HMS Walpole he spent time with his team in the Malta teacher.57 Another shore-based simulator for operators was the ‘Mass Procedure Teacher’.This was a row of simulated asdic huts, any one of which could be connected up to a single simulated asdic set. One student operator would conduct a simulated engagement while all the other students listened in so as to get used to the sounds made by different sorts of contacts.This was no idle period for the other students, as the instructor could switch control of the engagement between huts, so all had to be ready to take over at any moment. The training of ships’ teams at Portland appears to have been shared between the tactical and instructional departments. Ships of both 1A/S and the fleets used to go to Portland to conduct ‘work-up’, during which the whole ship’s team was taken through a series of exercises designed to develop their anti-submarine capabilities.There were 29 such standard exercises which varied in complexity from the anti-submarine operators keeping in contact with a passing submarine while the ship was at anchor to full-blown convoy defence and area patrol exercises. Exercises of particular interest to us were undertaken after the ships had proved themselves in a number of ‘set piece’ hunting and screening exercises, and are listed below: 20. Screening and counter-attack. Ships formed a screen around a notional main body58 and were attacked by a submarine. The ship which detected the submarine counter attacked and was then joined by one other ship from the screen to hunt the submarine and press home deliberate attacks. The submarine was allowed complete freedom of movement. 25. Search for a submarine sighted by A/S vessels. The submarine positioned itself on the surface as if conducting a transit. When the surface vessels sighted it they flashed lights to simulate gunfire, the submarine dived and a hunt was initiated. 28. Convoy exercise. Exercise in air and sea co-operation to protect a convoy and prosecute submarines detected while attempting to attack. 29. Shipping patrol exercise. Air/sea striking force defending shipping in the vicinity of a notional base.59

The experimental wing at HMS Osprey, substantially boosted by the movement of staff from the signal and mining schools, enjoyed a steady growth in the years following the rationalisation. HMS Cachalot, which had been used extensively for asdic trials, was transferred from Portsmouth to Portland, where it was used to great effect.A large tank in which controlled experiments 50 Copyright © 2003 George Franklin

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could take place was built but when it emerged that the reflection of sound from the edges of the tank was compromising some tests an experimental range was also built, just inside the breakwater in Portland harbour.Thus the scientists could experiment in the controlled conditions of the tank and on the sea range before embarking on the expensive and time-consuming business of fitting trial equipment to ships. The somewhat confusing chain of command in the experimental wing, with the Directors of Scientific Research, the Signal Division, and the Tactical Division all having close interests, combined with the mix of naval officers and civilian scientists to cause periodic difficulties. At the base of these was the almost inevitable tension between the service interest, which wanted to see newer and better equipment in service as soon as possible, and the scientific interest, which preferred to slow down production in favour of research into even more advanced technology. This conflict between the good and the best was nothing new, but nevertheless it seems occasionally to have soured relations. It may have been further exacerbated by the fact that naval officers, notoriously career-conscious at the best of times, generally spent around two years in a post, so were under pressure to demonstrate achievement over the short term, while the scientists could conceivably spend their entire careers in the same field. The most dramatic controversy came when, in 1930, Captain J.G.Grace, in his capacity as Captain A/S, wrote to his Commander-in-Chief complaining that the scientists were exercising too much control over production, and slowing it down in favour of long-term research. He went on to suggest that the senior scientist, B.S.Smith, should, notwithstanding his enormous experience of A/S research, be removed from his post. He was supported in his arguments by two former Captains A/S, but opposed by the Director of Scientific Research. This nicely divided the civilian and service camps, and the seriousness of the matter was indicated by the fact that Rear-Admiral H. J.S.Brownrigg was appointed to conduct an investigation. Brownrigg, probably to the long-term benefit of the navy, found largely in favour of the scientific community and, as well as suggesting some minor adjustments of the organisation, instructed Captain A/S that production should not take priority over progress. In hindsight, given that war was eight years away, that rearmament was five years away and that enormous advances were made over that time, Brownrigg’s decision seems to have been entirely correct.60 PRODUCTION OF ASDIC EQUIPMENT The whole asdic project was highly secret, especially in the earlier years of this study, though commercial application of the technology to the design of echo sounders necessarily meant that some of the principles reached the public domain. Nevertheless, the navy went to great pains to keep the design 51 Copyright © 2003 George Franklin


and performance as secret as possible, to the extent that quartz was referred to as ‘asdevite’ in order to disguise the design of the transducers, and the very term ‘asdic’ only ceased to be confidential in 1929.61 It has been argued that the exclusion of private enterprise from development slowed down the new technology, but given the calibre of the scientists working at both Teddington and Portland this is a questionable assertion. While final assembly of the equipment was without exception a service task, manufacture of individual parts could be contracted to private firms without indicating the components’ function. The London tombstone makers Farmer and Brindley initially, and slightly bizarrely, undertook cutting of quartz for asdic sets. This task later passed to the Signal School, but in the 1927 rationalisation went to Portland. The work was then subcontracted to two West Country firms, Childs of Yeovil, the ornamental masons, and the Bath and Portland Stone Firm. The latter purchased its cutting equipment from a company in Antwerp, and just before the fall of that city the Royal Navy, in an epic raid, recovered much of the equipment and staff of the Antwerp company to continue production of the cutting gear in the UK.62 Quartz, which was vital for the production of transducers but was not available in sufficient quantities from UK suppliers, was the most vulnerable aspect of asdic production. Difficulties were encountered in the early years, but by 1924 the supply was deemed satisfactory, and in 1932 there was sufficient reserve in the country for the manufacture of 800 transducers. By 1935, however, this reserve had reduced to sufficient for 650 transducers. By contrast, the production capacity of 35 sets per year63 in 1932 had by 1935 increased to an annual figure of 70, with a capability to produce 10 per week in emergency. In early 1938 there were 120 sets in reserve ready to be fitted to trawlers and other vessels taken up in the event of war,64 and in 1939 it was stated that 200 ships had been fitted with asdic and a further 200 sets were ready to be fitted to trawlers.65 Mechanical and electrical components were all manufactured by the dockyards until 1935, when some of their production was contracted out to civilian organisations.The dockyards, however, retained the capability to manufacture parts, in order to allow for rapid expansion in time of war.66 The dockyards also undertook construction of newly designed and experimental sets as well as harbour defence sets.The logic behind harbour defence sets being retained as a dockyard responsibility is obscure, but it may be due to the fact that, not having to be fitted to standard hulls, the sets could vary in design, making commercial ordering expensive. Companies involved in the manufacture of components included the Reed Paper Company and the Cambridge and Paul Instrument Company. Important components were divided between different companies to provide insurance against either commercial failure or bomb damage. Overall, by 1938 the production of asdic equipment was operating on a sound commercial basis, 52 Copyright © 2003 George Franklin

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with sufficient reserve capacity existing to allow for a rapid emergency expansion.67 The Admiralty Research Laboratory at Teddington, meanwhile, had been growing steadily since its establishment in 1921 and kept its role after the 1927 rationalisation.This laboratory, located next to the old National Physical Laboratory, boasted extensive facilities including a large concrete tank in which acoustics research could be conducted and, from 1927, a ‘rolling table’ which could simulate the pitch and roll of a ship at sea.The large community of scientists who worked at Teddington, developing a wide-ranging variety of naval equipment, was able to provide a useful degree of mutual support. Work on stable platforms for gun mountings and searchlights, for instance, carried out by one section, was of direct benefit to the asdic section, who were trying to produce a stabilised transducer. B.S.Smith—not to be confused with his assistant F.D.Smith or the Director of Scientific Research, F.E.Smith—headed the acoustics section at Teddington from 1920 to 1927, during which time they made good progress in fundamental research into underwater acoustics. Although no formal client/ patron relationship existed between Teddington and the other establishments, the more esoteric work undertaken at the Admiralty Research Laboratory undoubtedly enabled the mining and signal schools to continue their practical developments. In a similar way, the Portsmouth establishments could if necessary use Teddington as a problem solver. In summary, then, in parallel to the officers’ branch, a dedicated ratings’ anti-submarine qualification was formalised in the early 1920s, and the resulting branch grew with the number of asdic-fitted vessels until, at the outbreak of war, all destroyers and above had sufficient trained manpower to keep a 24-hour asdic watch, while the smaller escort and patrol vessels could keep a watch for 12 hours a day. Recruiting problems were encountered in the mid-1930s, but were overcome, and as equipment and tactics increased in complexity so the length of the training courses grew. A number of fishermen, and later trawlermen, were trained in A/S so as to man the trawlers that would be taken up in time of war, and although numbers fell short of those actually required for full manning of asdic trawlers, the Special Trawler Reserve nonetheless provided a useful core of expertise. Success with RNR ratings intended to man ships built in war was less complete, but again a core of expertise was developed. In any event, the increase in the training throughput at Portland during the late 1930s meant that the school’s transition from peace to war was relatively smooth. The very newness of the branch, however, meant that specialist representation in the Admiralty and the Naval Staff was limited to one or, on the eve of war, two officers, and most divisions of the Staff had only the vaguest idea of how A/S was developing. Following the massive expansions of the 1914 to 1918 war and the subsequent contraction, a rationalised set of shore establishments was 53 Copyright © 2003 George Franklin


established in the late 1920s to provide for the development and construction of material, the design of tactics and the training of personnel. The rate of scientific advance was, by any standards, impressive, and the short-term goals of career-conscious naval officers were largely subordinated to the desire of the scientific community to develop, in the long-term, the best possible equipment. There were, undoubtedly, destructive conflicts between the two communities, and a general paucity of funds meant that the Portland establishment, like the rest of the navy, had to fight for every penny and make do with sub-standard facilities. Following the Napier report, however, a properly thought-out and productive infrastructure did come into being. It is not surprising, then, to find that by 1939 Britain led the world in the development and employment of submarine detection systems. NOTES 1 2 3 4 5 6 7 8 9 10 11

12 13 14 15 16 17 18 19

PRO ADM 1/8766/66, Naval Staff Organisation, 1933; ADM 1/8778/183, Instructions for Naval Staff, 1934. It should be noted that this Smith has nothing to do with the Earl of Birkenhead, who as Lord Chancellor had also been F.E.Smith. Willem Hackmann, Seek and Strike: Sonar and the Royal Navy 1914–1954, John Murray, London, 1995, p. 101. PRO ADM 166/2105, Naval Staff Reorganisation, 1921. A/S specialist indicates an officer who has completed a long A/S course; for further explanation see the section on the A/S branch later in this chapter. PRO ADM 186 series. See, for instance, PRO CAB 53/29, COS paper 513, Appreciation of Situation in the Event of War Against Germany in 1939, prepared by the JPC for the Chiefs of Staff. Layard Diaries, 31 May 1933, Naval Museum Library. CHURCH CHAR 2/272, Letter from Chatfield to Churchill, 5 May 1936. PRO CAB 2/6, Minutes of 292nd meeting of the CID, 15 Apr. 1937. For a full discussion of the influence of the Staff structure on the development of A/ S, see G.D.Franklin, ‘A Breakdown in Communication: Britain’s Overestimation of Asdic’s Capabilities in the 1930s’, Mariners Mirror, 84, 2, May 1998. PRO ADM 116/2780, A/S Establishment at Portland—Organisation, note by Admiral Backhouse as controller, 9 Sept. 1931. PRO ADM 186/476, CB 3002 (29). NMM CHT 4/3, Letter from Chatfield, as First Sea Lord, to Churchill, dated 5 May 1936. NMM CHT 4/3, Letter from Churchill to Chatfield, dated 10 May 1936. Stephen Roskill, Naval Policy Between the Wars, 2 vols, Collins, London, 1968 and 1976, Vol. 2, p. 279. PRO ADM 1/8731/212, Development of the Anti-Submarine Service, memo from Capt A/ S to D of TD, 14 Mar. 1923. Ibid. PRO ADM 116/2410, Anti-Submarine Depot, Portland, 1924.


ORGANISATION 20 21 22

23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

50 51 52 53

54

Ibid.; Minutes of A/S committee meeting, 29 Feb. 1928. PRO ADM 116/3603, Appointment of Additional Officers to HMS Osprey, minute by DSD, dated 10 Aug. 1932. AFO 825/35, quoted in William Glover, ‘Manning and Training the Allied Navies’, in Stephen Howarth and Derek Law (eds), The Battle of the Atlantic: The Fiftieth Anniversary International Naval Conference, Greenhill Books, London, 1994. Glover, ‘Manning and Training’, p. 191. PRO ADM 116/2685, Destroyer Policy, 1928. PRO ADM 116/2410, Anti-Submarine Depot, Portland, 1924, and IWM 90/23/1, Memoirs of Captain John Mosse. Author conversation and correspondence with Admiral McGeoch. Roskill, Naval Policy, Vol. 1, p. 537. Author conversation with Capt. R. de L.Brooke. PRO ADM 1/12140, A/S Policy, Appendix D, ‘Training’. IWM 90/23/1, Memoirs of Captain P.J.Cardale. NML, Diaries of Lt-Cdr A.Layard. IWM DS/MISC/31, Diary of Admiral Ewing, 20 Sept. 1939. Ibid., 21 Sept. 1939. See Roskill, Naval Policy, Vol. 2, pp. 145–6, for a discussion of the timing of the removal of the ten-year rule. PRO ADM 1/8728/161, SD Branch. PRO ADM 186/519, Annual Report of HM Anti-Submarine Establishment, 1935. PRO ADM 186/547, Annual Report of HM Anti-Submarine Establishment, 1938. PRO ADM 1/12140, A/S Policy, 1938, TD memo Provision and Training of Anti-Submarine Personnel, dated 14 June 1937. PRO ADM 1/10092, A/S Training, Note by D of TD, 24 Nov. 1938. PRO ADM 196/519, Annual Report of HM Anti-Submarine Establishment, 1935. PRO ADM 116/4003, Ships, Boats etc Required for a Far East War. Ibid., Minute by D of P, dated 7 Aug. 1934. PRO ADM 186/527, Annual Report of HM Anti-Submarine Establishment, 1936. Ibid. PRO ADM 186/536, Annual Report of HM Anti-Submarine Establishment, 1937. PRO ADM 116/4005, List of Trawlers to be Taken up for War, D of P minute, 26 Nov. 1937. PRO ADM 1/10092, A/S Training, Board Decision, 9 Jan. 1939. Hackmann, Seek and Strike, p. 109. It is important to note that there were two separate organisations at Portland, HMS Osprey, which was the A/S school, and the dockyard, which acted as a basing facility for, among other ships, 1 A/S. PRO ADM 239/248, CB 3212, Technical Staff Monographs 1938–1945, A/S Warfare, Vol. IV, A/S Training. PRO ADM 116/2607, Sloop Requirements, Minute by D of TD, dated 23 Nov. 1932. PRO ADM 116/2410, Anti-Submarine Depot at Portland. It is interesting to note that Capt A.J.Murray, who was DSD’s representative on the Napier committee, became Capt A/S in Dec. 1928, so inheriting the fruits of his labour. PRO ADM 1/8699/117, D of TD bidding for expression of Board Appreciation, 6 Apr. 1928.


BRITAIN’S ANTI-SUBMARINE CAPABILITY, 1919–1939 55 56 57 58

59 60 61 62

63 64 65 66 67

PRO ADM 116/2410, Anti-Submarine Depot at Portland. Author conversation with Capt. R. de L.Brooke, Apr. 1997. Layard Diaries, Naval Museum Library, Portsmouth. Throughout the book, the term ‘main body’ will be used to describe the submariner’s target. This main body could be the battle fleet, a troopship, a merchant convoy or a single stricken vessel. PRO ADM 186/140, CB 1868/1931, Anti-Submarine Practice Memoranda. PRO ADM 116/2780, A/S Establishment at Portland—Organisation, and Hackmann, Seek and Strike, pp. 122–5. PRO ADM 186/476, CB 3002 (29), p. 28. Hackmann, Seek and Strike, p. 171. Hackmann cites Bezzant, Out of the Rocks, but describes Bezzant’s account as being ‘not entirely the same’ as that given by the involved parties. PRO ADM, 116/3603, Appointment of Additional Officers to HMS Osprey, DSD minute, dated 22 Jan. 1932. PRO ADM 1/12140, A/S Policy, TD memo, ‘Anti-Submarine Policy Regarding the Use of Asdics’, Jan. 1938. PRO ADM 186/547, Annual Report of HM Anti-Submarine Establishment, 1938. PRO ADM 186/519, Annual Report of HM Anti-Submarine Establishment, 1935. PRO ADM 186/547, Annual Report of HM Anti-Submarine Establishment, 1938.


3

Sensors

INTRODUCTION At the end of the First World War passive directional hydrophones were being used with some success to search for submarines, but, while some active echo ranging systems were at sea, no operational use had yet been made of them. It was soon decided that active systems held more long-term potential, and research into passive acoustic means of detection fell off, being almost totally abandoned by 1930. German progress into passive means continued, and in 1937 the Admiralty purchased a German hydrophone system to determine how effective it was. Unfortunately, this submarine system was fitted not to a submarine but to the surface ship HMS Viscount for the trials, and the results obtained indicated that it was less effective than might have been the case had a more appropriate platform been used. A proper appreciation of the value of passive acoustic sensors would have altered both the perception of German methods and the development of British tactics. This, however, is discussed at greater length in Chapter 6. Active sensors, meanwhile, were developed apace both for surface ships and for submarines, and the systems available in 1939 would have been unrecognisable to the men who worked with the 1919 systems. One spin-off from the work on hull-mounted asdic was the development of harbour defence asdic, which could be installed on the seabed to detect attacking submarines. Harbour defence could also be provided by physical barriers or by indicator loops, which consisted of seabed cables in which a passing submarine would induce a current. The commonly stated origin for the word ‘asdic’ is as the acronym for the Allied Submarine Detection Investigation Committee. However, Hackmann argues that there was no such committee, and no sign of any such committee has come to light in the research for this book. It seems that the standard explanation was produced in December 1939 after Churchill had used the word in the House of Commons and the compilers 57 Copyright © 2003 George Franklin


of the Oxford English Dictionary asked the Admiralty for its origin.1 Hackmann argues that the explanation given in the 1924 Portland Report2 that the word stood for ‘pertaining to the Anti-Submarine Division’, i.e. ASD-ics, is far more likely to be correct. In the extensive research for this book, both in First World War and inter-war archives, no mention has been found of the seemingly apocryphal committee, and Hackmann’s explanation would appear to be correct. One can conclude, therefore, that an Admiralty official who, three months into the war, had more immediate things to do than answer etymological queries from Oxford, found it expedient to make up a reply, which duly became accepted truth. The fact that the literature has, with the exception of Hackmann’s book, slavishly repeated an evidently incorrect explanation is symptomatic of the lack of attention that has been paid to the general subject. SURFACE SHIP ASDIC Surface ship asdic equipment generally consisted of a transducer which protruded from the hull and was housed in a dome, and an asdic control office from which the equipment was operated.The asdic control position tended to get closer to the bridge as designs advanced, and in some trawler systems was even placed on the wheelhouse roof. In any event, good liaison between the bridge and the control position was vital. Figure 3, which actually shows the arrangement of a type 114 set, gives a good idea of the generic layout. The first series of ships to be fitted with operationally effective asdic sets were the ‘P’ and ‘PC’ boats of 1 A/S, which received the type 112 equipment in the early 1920s. Housed in a retractable canvas dome, the type 112 was manually trained onto the submarine bearing, and the operator had to compensate for movement of the ship by constantly moving the transducer to follow pitch and roll indicators. A series of geared rods repeated the transducer’s bearing to an indicator on the bridge. The operator wore a headset in which he could hear both the outgoing pulses and the returning echoes, and range was determined using a stopwatch; he used a morse key to make transmissions.The experimental whalecatchers Icewhale and Cachalot also received crude versions of this fit, which they could deploy over the ship’s side. The type 114 was the first destroyer set, and entered service on board HMS Rocket in 1922. At first these sets included a solenoid-operated stopwatch that was connected to the transmitting equipment in an attempt to improve range accuracy, but this was not a success, and the operators once again found themselves using manual stopwatches. This type also had a retractable dome, but the dome was made of canvas, and thus very fragile, and retraction was a laborious process involving block and tackle in a number of stages. In technical terms the set was more advanced than the type 112, but little had changed in the practicalities of use.When the design had been 58 Copyright © 2003 George Franklin

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Figure 3: Type 114 Asdic Set, Showing Typical Arrangement of Equipment (Source: PRO ADM 186/758)

standardised, these sets were fitted to HMS Heather and the ‘V’ and ‘W’ destroyers of the 6th flotilla. The equipment developed thus far had only been capable of sweeping a 5-degree arc with each transmission, so sweeping a large arc involved a number of separate transmissions, between each of which the transducer had to be manually trained by the operator onto the new bearing. This took time, and, as will be discussed in Chapter 6, presented tactical difficulties for the Commanding Officer. In an effort to overcome this, the Signal School researchers attempted to adapt the type 114 so that it would make the initial search sweep over a much wider arc, later refining the bearing should a contact be detected. 59 Copyright © 2003 George Franklin


In the event, adaptation of the type 114 was not successful, and a completely new wide-angled set, the type 115, was developed in 1923. This system was designed to transmit initially over a 180-degree arc, and then to narrow the arc of transmission to localise a detected contact. In order to expedite this bracketing, the type 115 was fitted with an electrical training mechanism, which proved considerably faster than manual training. The sweeping efficiency of the type 115, however, never came up to acceptable standards, and it was soon abandoned. This was regrettable, because such a development would have caused a quantum leap in asdic tactics. Eventually, the scientists went back to working on narrow-angle gear, and the equipment being used in 1939 was still only capable of sweeping over a five-degree arc. Another innovation in the type 115 was the streamlined steel dome, which replaced the 114’s cylindrical dome and allowed ships to operate at speeds in excess of 15 knots. Unfortunately, the dome tended to crush under the pressures encountered at around 20 knots and, being bolted on to the hull rather than retractable, this limited the top speed of the ship, whether operating asdic or not.This was clearly not satisfactory for destroyers whose primary role remained fast torpedo actions around the battle fleet and, although the 2nd destroyer flotilla was fitted with type 115s, the set was not popular among Commanding Officers. The pause in destroyer construction in the 1920s also caused a pause in the production of new asdic types. The development teams were, however, far from idle over this period, and it is even likely that, spared the pressing need to get a set into service, they were able to make faster and betterorganised long-term progress than had previously been the case. In any event, the type 119, which came into service some seven years after the type 115, was a huge improvement on the old set, and was described as ‘the basis of destroyer asdic sets for some time to come’.3 After trials it was fitted in the ‘B’ class ships of the 4th destroyer flotilla, the first ships to be built under the accelerated construction programme described in Chapter 5. The set included a number of new developments, including electric training that could be controlled from either the operator’s position or the bridge, a mechanical range indicator and a facility to automate transmissions. Further, the type 119 was the first surface ship set to include a loudspeaker, which allowed the bridge team to listen for echoes, and, in the case of a well-worked-up team, pre-empt the reports of the operator. This loudspeaker, with its constant pinging, was a standard fit for subsequent sets, and became a compulsory feature of all Battle of the Atlantic films. For training purposes the type 119 was fitted with a procedure teacher and a signal injector, which allowed ‘simulated’ contacts to be fed into the system for analysis by teams under training. The streamlined dome that housed the type 119 was, like that of the type 115, bolted to the ship’s hull, but was considerably stronger, and did not limit 60 Copyright © 2003 George Franklin

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the ship’s speed in the way the previous model had. It is worth pointing out at this stage that the design of a sturdy dome that had the required properties of acoustic transparency and a shape that was streamlined so as to avoid noise developing in eddies was one of the greatest problems asdic’s developers faced. In pursuit of a satisfactory solution, and despite the fact that domes regularly leaked or came away from hulls altogether, two of the development engineers appear, astonishingly, to have had themselves bolted inside hull-mounted domes in order to study the domes’ behaviour once submerged.4 The type 121, which from 1932 was fitted to the ‘D’ class of destroyers, was in electronic terms much the same as the 119, but benefited from a gyrostabilised transducer to take account of the ship’s pitch and roll, and a retractable dome.This meant that when the ship was engaged in the classic destroyer role, or when steaming towards a previously reported submarine, the dome could be withdrawn into the hull, removing risk of water pressure crushing the dome, and the reduction in drag marginally increased the ship’s maximum speed. The type 121 was later fitted to the ‘E’, ‘F’ and ‘G’ class destroyers, and was used with success throughout the war. It was also fitted, in an experimental role, to the early sloops. It was not, however, considered suitable for mass fitting to sloops, and the bulk of the operational sloops were fitted with the type 127, discussed later. The years 1933 and 1934 saw the introduction of two trawler sets, the types 122 and 123. The former, using steam from the trawler’s system, produced its own electricity, while the latter was for fitting to trawlers which already had an adequate electrical generation system. Hackmann describes the operation of these sets: Transmission was initiated either automatically by the distance finder…or manually by the send/receive key.The control position was a shelter constructed on top of the wheelhouse; the operator stood behind the binnacle and trained the transducer by a hand-wheel connected to it by a flexible drive. Its bearing was indicated by a light spot projected on the magnetic compass card.The captain stood with the asdic operator during an attack and shouted his commands to the helmsman on the voice pipe.5 Illustration 6 shows the desperately exposed arrangement of the operator’s position. The underlying principle in both the trawler sets was simplicity of both construction and maintenance, so that they could be mass-produced in war, and then maintained and operated by trawlermen with the minimum of training. The type 123 especially proved reliable both during pre-war exercises and throughout the war years, though the inherent problems in using trawlers as A/S vessels, described in Chapter 6, remained. 61 Copyright © 2003 George Franklin


The type 124, which superseded the type 121 destroyer set, was similar to its predecessor in most respects, but boasted a chemical range recorder. This device, which gave a diagrammatic indication of the range, made the Commanding Officer’s job a great deal easier as he had an immediate indication as to whether he was closing or opening up on the submarine, and consequently any change in submarine course would become rapidly evident. This range recorder was an extremely sophisticated piece of equipment and, although modified, remained the standard equipment throughout the war. In its more advanced form it also gave an indication of the time to drop depth charges, so obviated the mental gymnastics which had previously been required. The type 127 sloop set, mentioned above, was essentially a hybrid of the 122 and 123 trawler sets, but had an additional, gyro-operated, bearing indicator on the bridge. The operator worked in a small hut on the upper deck near the bridge, but the Commanding Officer was still exposed to the elements on the open bridge. This set was widely fitted to sloops, minesweepers, old destroyers and various other ships and, although like most other sets it underwent periodic modification, it gave good service throughout the war. The final destroyer set with which we are concerned is the type 128. Trained using a mechanical wheel, operated from a hut on the bridge and having a fixed dome, in some ways it represented a retrograde step, but it was ideal for ships which lacked the space for more complex arrangements. Having entered service in 1938, this set was widely fitted before, during and after the war. The type 130, intended for use in fast anti-submarine motor boats, designated M A/S Bs, represented a departure from the design philosophy employed in larger ships.The transducer could not be steered, but was fixed facing either forward or, in one set of experiments, towards the beam. The best results were achieved with the asdic operator himself steering the boat towards the contact, though this was reported to be ‘strenuous’, and perhaps unsuitable for wartime conditions. The transducer was mounted on a streamlined strut which projected below the hull of the boat, in order to keep the transducer out of the disturbed surface water around the hull, and trials were initially successful. A fuller study of these boats, which must have been tremendous fun to operate, is provided in Chapter 5. The final pre-war surface ship set was the type 138, which was intended as a self-defence set for large surface ships. Technologically advanced, this set included separate active and passive transducers, each electrically steerable and gyrostabilised, all housed within a retractable dome. The receiving apparatus included specially designed recorders as well as headphones and the now standard speakers. This set was not intended to allow cruisers, battleships or aircraft carriers to attack submarines, which would have been folly, but, instead, would allow the major units to take avoiding action and 62 Copyright © 2003 George Franklin

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guide escorting vessels to the submarine’s position. There is no record of this essentially sound principle having had any success at all in war, and certainly in the actions studied in Chapter 7 no reference has been found to major units detecting submarines before or during their attacks. SUBMARINE ASDIC Asdic was used in submarines both in the active mode, for approaches to other submarines, and in the passive mode for approaches to noisier surface ships. Early trials indicated that submarine asdic was sufficiently effective, against both surface craft and other submarines, to justify a policy that all post-1928 submarines would be fitted.6 The first submarine set was type 113, which was in most respects identical to the type 112 described above, but was inverted so the transducer protruded from the top of the casing, rather than the bottom of the hull, as did the surface ship set. The submarine H 32 trialled the type 113 in 1922, and it was found to be effective against surface ships.The initial design had a canvas dome, which proved unsatisfactory as it only achieved acoustic transparency some 30 minutes after diving, before which time the submarine effectively had no asdic.Various alternatives were tried, including copper. Hackmann reports that the copper dome was not popular with submariners; being of a polishable material, it was required to shine, and many hours were spent by luckless sailors standing on the casing working with rags and metal polish when there was other, more productive and probably less demoralising, work to be done. The next submarine set to be developed, in 1926, was the type 116, which incorporated a vertical tube that passed through the pressure hull. The idea behind this was that the pulse could, effectively, be transmitted from either the top or the bottom of the submarine, so allowing it to operate on the surface or sitting on the bottom, where diesel submarines used to spend a fair amount of their time. This tube has been described as: A dangerous practice not much favoured by the underwater mariners. In fact during the deep diving acceptance trials off the Isles of Scilly the boats were found to leak like sieves, and one First Lieutenant (later to become a Rear Admiral) went about with an open umbrella.The asdic office, which was sited in the bilges, always held the record for the depth of water splashing about. No doubt most of the water entered through other minute orifices, but this large tube penetrating the hull cannot have added to the spiritual or physical well-being of the ship’s company.7 A less dramatic innovation included in the type 116 was the inclusion of a loudspeaker in the receiving circuitry, similar to that already being used in surface ships. Overall, although it had a more satisfactory steel dome, the 116 63 Copyright © 2003 George Franklin


was not a success, and it was replaced after only two years by its successor, the type 118. This was a less ambitious design, with a single dome mounted on the underside of the boat. The transducer was still trained by hand, unlike those of the contemporary surface ship sets, but in other respects it was a technological and design improvement on its predecessor.The 118 remained in service throughout the inter-war years, and some sets saw action in the war, though it is unclear how, or whether, they were able to sit on the seabed without damaging the dome. The successor to the type 118 was the type 120, which was fitted to the River class submarines and the early ‘S’ class. This set differed very little in practical application from the type 118. The final inter-war submarine set was the type 129, which entered service in 1937. This was initially fitted to the ‘T’ and ‘U’-class submarines, and as the transducer was located in a strengthened cage forward, it could be used when the submarine was surfaced, submerged or sitting on the bottom. Significantly for anti-submarine operations, this set was effective as both an active and a passive equipment, so could be employed silently against a surfaced boat running on diesels, or, with some risk of counter-detection, in the active mode against a quieter dived boat. Making use of the remarkable developments which had taken place since 1919, it was electrically steered and gyrostabilised and could, when employed passively, turn slowly and continuously to provide an all-round listening capability. INDICATOR LOOPS Indicator loops, which should not be confused with the very much less technical indicator nets described later in this chapter, were a means of using a submarine’s electromagnetic influence to detect it as it passed over a wire loop. A loop would be laid across a harbour entrance or another channel likely to be used by attacking craft, and a nearby shore coastal station would be established. As a submarine, or any other metal craft, crossed the loop the induced current would move a galvanometer needle in the shore station, alerting the defenders to the presence of the submarine. All that would be known about the submarine was that it had crossed the loop at a given time, and no information would be available about exactly where it had crossed, what direction it had crossed in or where it had gone since. The information provided, however, would be enough to alert the defenders, allowing local patrol craft to increase their vigilance, and giving ships in the harbour time to take appropriate defensive measures. As early as 1929 experimental loops were being laid at Portland, off the Firth of Forth, at Malta and in Bantry Bay in south-west Ireland. Among other early teething problems with these loops, it was found that they tended to drift and move under the influence of the tidal stream and, in shallow 64 Copyright © 2003 George Franklin

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water, during heavy weather.To counter this effect HMS Vernon produced a cable specially weighted with lead, and, although not absolutely proof against such perturbations, this was found to be more satisfactory than previous models. In the early 1930s the experimental loops began to be replaced by equipment which was considered to be operationally effective. The three loops that had been laid at Portland were lifted in 1935 and supplied, complete with their instrumentation, to the Mobile Naval Base Defence Organisation (MNBDO).8 Although they were never used to support a mobile base, the fact that they could be lifted, stored, moved and re-laid demonstrates their flexibility and utility.The specialist vessel Kilmun laid an indicator loop of the type proposed for the MNBDO at Lamlash on the Clyde in 1935, with the operators working and living under canvas ashore.The equipment appears to have worked effectively, and no particular problems were encountered in the laying, operation or recovery. By 1936 the effectiveness of indicator loops and their role on harbour defence were sufficiently established to justify the cable layer Lasso being included in that year’s estimates in order to accelerate the laying programme. In 1937 it was reported that loops had been laid off the Firth of Forth and Singapore,9 and the 1938 Portland report stated that a loop had been laid off Portsmouth and that others were planned for Plymouth, Malta and Hong Kong in the near future. By 1939 the equipment had been so perfected that indicator loops in general were described as ‘99 per cent effective so long as they are electrically correct’.10 That 99 per cent, of course, referred only to the detection of the submarine. The efficacy of the system still relied on the ability of the local patrol craft to localise and engage the detected boat. Given that the majority of such local patrol craft would have been trawlers whose crews had received the absolute minimum of training, confidence cannot have been high. The predicted effectiveness of indicator loops, however, made them popular with local commanders. The Commander-in-Chief Portsmouth, for instance, despite already having a loop in the immediate approaches to the harbour, requested a further loop to the south of Nab Tower (off the eastern entrance to the Solent) to give early warning of the approach of a submarine. At the same time a similar proposal was being floated for the seaward defence of the Firth of Forth.11 The Admiralty turned down both suggestions. HARBOUR DEFENCE ASDIC Harbour defence asdic, or HDA, was a more precise means of detecting or localising a submarine as it approached a harbour or anchorage.A number of electrically steered transducers, similar in most respects to ship-fitted sets, would be laid on the seabed and controlled from a shore station. Although initial detection was less sure than with an indicator loop, HDA gave the 65 Copyright © 2003 George Franklin


operators the precise position of the submarine, and allowed them to track its movement.A good radio liaison between the control station and the local patrol craft then afforded a fair chance of the contact being ‘handed over’ for prosecution. An inverted dome for a harbour defence asdic was under development in the 1920s, and the first workable set was installed off Portland in 1932.12 Water pressure at depth remained a problem, however, and in 1935 sets were only useful to depths of 40 fathoms.13 This was gradually overcome, and in 1937 a set capable of working at 100 fathoms was installed off Portland.14 A harbour defence asdic trial took place at Portland in 1935 during which an approaching submarine was detected by the device and a trawler was guided by radio to the position of the submarine.The equipment itself and the liaison between the shore-based controllers and the patrolling trawler both appear to have worked well, but the equipment was still not considered to be totally effective. The report concluded that it should be used in conjunction with indicator loops. The 1936 and 1937 estimates allowed for the purchase and establishment of two harbour defence asdic sets off Portland, and by the end of 1937 the Admiralty had procured systems for the protection of Plymouth, Berehaven, Queenstown, Portland and the Firth of Forth, as well as one set which would be used for the MNBDO. In February 1938 the Director of the Tactical Division approved the fitting of a number of HDAs, and in August a ‘Firth of Forth Defence Test’ took place.This involved all the static defences being activated and the proposed local defence group of trawlers, namely Amethyst, Agate and Jasper, working in support. Against these were set two submarines, tasked to get as far up the estuary as possible. Regrettably, no results from this exercise survive, but the very fact of it having taken place indicates that the defences were being readied for war by the autumn of 1938.15 In response to the worsening international situation, the First Sea Lord issued an instruction on 21 August 1939 that the A/S defences, including ships, HDAs and indicator loops, should be manned and activated in the Firth of Forth, Portsmouth and Plymouth. INDICATOR NETS AND BOOMS Perhaps the surest way to prevent a submarine from entering a harbour, or a defended anchorage, was to erect physical barriers in its way. As Günther Prien discovered in penetrating Scapa Flow in October 1939 to sink the Royal Oak, a small gap in a physical barrier could be exploited with devastating success, but preventative measures were generally successful. The science of sinking a blockship across a channel holds few secrets, but the anti-submarine nets that were developed and procured between the wars are worthy of mention. 66 Copyright © 2003 George Franklin

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There were two broad types of net which were employed by the navy. The heavier type, which was designed to act as a physical barrier to stop the progress of the submarine, was firmly fixed to the seabed, generally had some form of impediment over it on the surface and was known as a boom. Where there was a necessity for friendly ships to pass through the boom, some form of gate would be provided. The second type, which tended to be much lighter, was known as an indicator net.This made no attempt to arrest the progress of the submarine, but would be dragged along by a submarine which ran into it, thus revealing the boat’s presence and location to watching vessels.The former were more expensive to build, but could be left alone once laid, while the latter were cheaper to produce and lay, but needed to be watched constantly if they were to be effective. Anti-submarine booms and their associated net systems were precisely the sort of equipment which lent itself to rapid procurement in an emergency. They contained no small or moving parts, they could be constructed by any firm with experience in the production of wire ropes, and they could be produced and fitted relatively quickly. In short, to buy them before any direct threat of war was evident, either to lie in storage or be fixed in place, would only have been wasteful. The model, therefore, was to perfect the design in the early inter-war years, perhaps performing trials, and then leave the design ready to be taken up when required. As the international situation worsened, capacity for production could be investigated, and following a given trigger they could be bought and fitted as required. Following this pattern, extensive tests and trials were carried out throughout the inter-war period, and, from 1937, ‘Boom defence gear was provided for naval and commercial ports at home and abroad with an abundance undreamed of a few years earlier.’16 In the mid-1930s the concept of the Mobile Naval Base, which would allow a fleet to be supported and sheltered anywhere in the world, was gaining in vogue. The defences for such a base would require a rapidly deployable A/S shield, which could be spread around a fleet in an unprotected anchorage. The nets being used at the time were made from 2-inch rope, which was too heavy to be carried on or laid by fleet units, so it was proposed that experiments be undertaken with 1½-inch rope. By using such light nets, it was hoped that the fleet could build its own barrier, and there would be no need for a specialist net-laying ship, such as HMS Guardian, to stay with the fleet. The Director of the Tactical Division pointed out that light nets had failed in the war and during the 1926 trials, but nevertheless a new trial was attempted. In the event, the submarine was able to penetrate a single layer of 1½-inch net, and in some cases did not even notice having hit the barrier. It was, however, suggested by the Director of Torpedoes and Mining that the light net might be useful if only lightly moored. In this way, it was hoped, the net could be persuaded to move once hit by a 67 Copyright © 2003 George Franklin


submarine, so indicating the submarine’s presence, rather than staying fixed to the seabed and developing enough pressure against the submarine’s cutters to allow them to break the net. This would seem to have been the first occasion when the distinction was made between indicator nets and those which aimed to stop the submarine. One design that does appear to have been tested incorporated a surface boom and short lengths of indicator net that pulled away giving relatively little resistance when hit by a submarine, which would thus not realise that it had been detected. As the special ‘parting clips’ let the net slip, flares would be illuminated to alert patrol vessels. Possibly as a reaction to these trials, one of HMS Guardian’s officers, Lieutenant-Commander R.Edwards, later Admiral Sir Ralph Edwards, KCB, CBE, produced a useful paper outlining the general situation with respect to indicator nets.17 From this paper we learn that light indicator nets came in panels 300 feet long by around 70 feet deep, each panel weighing half a ton. These light nets were made from 3/8-inch flexible steel wire in a 4-foot mesh, and they could be laid from a warship’s boats. The heavy indicator net, meanwhile, came in 200-foot panels which were 90 feet deep and weighed three and a half tons. These were constructed of 1½-inch rope wire in an 8-foot mesh, and had to be laid and recovered by a specialist ship. These figures, however, conflict with evidence found elsewhere that the heavy net, known as the B1 type, came in panels which were 200 feet by 108 feet, and the lighter nets, known as type B2, came in lengths of 255 feet and depths which varied between 30 feet and 120 feet.18 Lieutenant-Commander Edwards’ report also tells us that the net-laying ships could have around 1½ nautical miles of net ready and rigged for almost instant laying, and had enough equipment on board to lay another section of the same length. The second length would have to be prepared on deck, however, and would not be laid for another four days. In good weather it took 24 hours to recover three-quarters of a nautical mile of net, but this would have to be laid out and re-rigged before being laid again, a job which took three days and really required the net to be landed. On the tactical side, it was felt that the distance between a net and the ship it was protecting should be a mile further than the submarine’s predicted engagement range.19 For the latest boats, firing against a stationary target, this would mean laying the net around 8,000 yards from the anchored ships. A circle with a radius of 8,000 yards has a perimeter of around 25 miles, so for the 1½ miles of instantly available net to be effective, an anchorage with a good deal of natural protection would clearly be required. To put the effectiveness of the net-laying ship into perspective, however, it should be borne in mind that the strategically important ports, such as Shanghai, Singapore and Darwin, were generally provided with a good degree of physical protection. In parallel to the ‘B’ type indicator nets, the navy was working on 68 Copyright © 2003 George Franklin

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‘A’-type nets aimed at barring a submarine’s passage. The type A3, which was made of two layers of 4-inch steel wire rope mesh, was tested and found to be satisfactory in 1929 and 1931, production being authorised after the second set of trials.The type A2 was similar, but consisted of only one layer of mesh. Both these types were trialled again in August 1939 with a submarine using explosive cutters. The cutters enabled the submarine to pass through the A2 net, but the A3 net stopped it. Even the passage of the A2 net must have been difficult, and one imagines that even the crudest passive listening set could have detected the detonations of the cutters, so revealing the submarine’s presence. The standard boom appears to have consisted of an 8-foot by 8-foot mesh of 3-inch wires, moored to the bottom and given large floats at the top. In especially vulnerable areas, or where it was important to exclude submarines, a near-rigid boom would be constructed over the top of the mesh to prevent a surfaced boat crossing the net at high tide. In response to a fear that midget submarines, with an external diameter of 6 feet, might get through the mesh, a mesh measuring 8 feet by 4 feet was trialled, but the drag of the tidal stream was too great for the conventional anchoring mechanisms. The expected endurance of a net was stated in 1939 to be around six months, but it is not clear if this estimate derived from previous war experience, inter-war trials or wild guesswork.20 It was stated as policy, in 1939, that nets would not be laid in less than 5 fathoms (30 feet) of water, as this was held to be the minimum depth required to operate a submarine. At the other end of the depth scale, it was not considered effective to lay nets in depths of more that 15 fathoms. The first recorded inter-war tests of static barriers were in 1925, when an ‘L’-class submarine was used to test the effectiveness of the current model of gate.The 4-inch rope then in use appears to have been proof against the knife cutters which were fitted to the submarine, but there remained some doubt about the effectiveness of the barrier against a submarine armed with explosive cutters. Full-scale trials of a boom system took place in 1931, and seem to have been successful, but trials of an improved gate planned for 1934 were postponed. According to a minute by the Director of Torpedoes and Mining, the logic of which remains obscure, this cancellation was because of the excessive pressure on production of both gates and booms.21 In the late 1930s, a type A/B net was devised which would fulfil the functions of both types A and B. This was a heavy net which hung from a floating boom by detaching clips. When a submarine hit it, the net would detach from the boom and fall on to the submarine, which would then be so encumbered that it would be unable to proceed. The detaching of the net from the boom would also alert watching patrol craft to the presence of the submarine, which in its encumbered state would be more than usually liable to attack. Trials were undertaken in 1938 and 1939 to test the effectiveness of these 69 Copyright © 2003 George Franklin


nets.The unfortunate submarine chosen to drive itself deliberately at these underwater obstacles was HMS Seawolf, under the command of LieutenantCommander Studholme.The trials indicated that a double line of nets was 100 per cent secure against penetration. A single line was effective only if the submarine was not fitted with a full set of cutters, but Rear-Admiral Submarines said that the risk to the boat was such that he would not send a submarine against even a single line. It was also concluded that, if there was no boom over the nets, a daring submarine commander could slip over the top of the net at high tide, the Seawolf having done exactly that when trimmed down on the surface and drawing only 14 feet. The gate, which was reinforced but not designed to fall on top of the submarine, was found to be effective, stopping the submarine altogether when she hit it at 41/2 knots. It was felt that the surest way to penetrate such a defence was by going through the gate with or behind a ship for which it had been opened. In order to avoid U-boats getting through by either of these means, it was recommended that trawlers be employed to patrol around gates and over nets which lacked booms, and hydrophones or harbour defence asdics would be fitted around gates.22 Although Seawolf was only fitted with mechanical, rather than explosive, cutters, the trial results must have been reassuring for the Director of the Local Defence Division, much of whose bailiwick would have been protected by such nets. These tests had clearly been anticipated, as the fitting of specially constructed gate defence vessels with asdic had been declared policy in January 1938.23 A number of these gate defence vessels were procured during the late 1930s, and specialist boom defence vessels of the Bayonet class were ordered under the 1937 and 1938 estimates. A second net layer, the HMS Protector, of 2900T, had already joined the HMS Guardian in 1936, and that year’s estimates provided for extra gate vessels and boom working vessels exactly to indicate ‘the Admiralty’s intention to complete the defences of our more important ports’.24 The bulk of the work conducted on A/S nets over the inter-war period was concerned with protection of harbours and anchorages, but the nets could be used for larger projects as well. In the First World War, for instance, barrages had been attempted across the Straits of Dover and Otranto, as well as the northern part of the North Sea. Of these, however, only the Dover barrage had enjoyed practical success, and that had been at enormous cost in material for the barrage itself, as well as boats and men to watch it. Furthermore, huge numbers of mines were used to back up the nets, and the whole area presented a general hazard to navigation. The inter-war thinking about such large-scale projects was that they were generally inefficient, but watched nets were still considered to be an effective way to prevent submarines from entering small areas such as harbours.25 In summary, it can be seen that considerable advances were achieved in submarine detection from both static and moving platforms. In particular, 70 Copyright © 2003 George Franklin

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the revolution provided by surface ship asdic shook the impression of invulnerability that had been enjoyed by First World War submariners. It will be argued in Chapter 6, however, that these advances were seen in their proper perspective, and that the navy as a whole did not regard asdic as being the panacea to the submarine problem. NOTES 1 Willem Hackmann, Seek and Strike: Sonar and the Royal Navy 1914–1954, John Murray, London, 1995, p. XXV, citing ADM 1/9880. 2 Hackmann cites ADM 186/244, but the quote is actually in PRO ADM 186/444, CB 3002 (24), p. 19. 3 PRO ADM 186/491, CB 3002 (31), p. 35. 4 Hackmann, Seek and Strike, p. 176. 5 Hackmann, Seek and Strike, p. 214. 6 PRO ADM 186/476, CB 3002 (29), p. 28. 7 Hackmann, Seek and Strike, p. 207. It is worth noting that the German type XB minelaying submarine had a number of vertical mine tubes which passed through the pressure hull, and there is no record of this having caused problems for the submarines. 8 PRO ADM 186/519, Annual Report of HM Anti-Submarine Establishment, 1935. 9 PRO ADM 186/536, Annual Report of HM Anti-Submarine Establishment, 1937. 10 PRO ADM 1/9855, Firth of Forth A/S Defences, 1939. 11 PRO ADM 116/4139, UK Harbour Defence, Paper from C in C Portsmouth to the Admiralty, 15 July 1939. 12 PRO ADM 186/500, Annual Report of HM Anti-Submarine Establishment, 1932. 13 PRO ADM 186/519, Annual Report of HM Anti-Submarine Establishment, 1935. 14 PRO ADM 186/536, Annual Report of HM Anti-Submarine Establishment, 1937. 15 PRO ADM 1/9847, Harbour Defence Asdics, 1939. 16 G.A.H.Gordon, British Seapower and Procurement Between the Wars: A Reappraisal of Rearmament, Naval Institute Press, Annapolis, MD, 1988, p. 176. 17 PRO ADM 116/4004, Gate and Boom Trials, Paper by Lieutenant-Commander Edwards, dated 26 Feb. 1934. 18 PRO ADM 116/4004, Gate and Boom Trials, Admiralty paper dated Aug. 1934. 19 In fact, a mile beyond the torpedo danger zone (TDZ), discussed in Chapter 6. For anchored ships, however, TDZ was essentially the same as the submarine’s predicted engagement range. 20 PRO ADM 1/9855, Firth of Forth A/S Defences, 1939. 21 PRO ADM 116/4004, Gate and Boom Trials, DTM docket, ‘Double Line Gate for A/ S Booms: Progress’, Minute dated 23 Mar. 1934. 22 PRO ADM 1/9854, Anti-Submarine Booms for Harbour Protection, 1939. 23 PRO ADM 1/12140, A/S Policy, TD memo, ‘Anti-Submarine Policy Regarding the Use of Asdics’, dated Jan. 1938. 24 Board Minute 3423, 16 Nov. 1936. 25 Lieutenant-Commander D.G.Wemyss, ‘The Submarine and its Antidotes Today’, RUSI Journal, May 1929.


4

Weapons

THROWN WEAPONS Weapon design was probably the weakest area of A/S development between the two world wars.The depth charge, unsophisticated and only moderately effective, was the main weapon in 1939, as it had been in 1919, and underwent only minor modification. Specialist aircraft weapons advanced further in relative terms, but in absolute terms they progressed from being non-existent in 1919 to being virtually useless in 1939. The greatest criticism that has been levelled against the Royal Navy in this field concerns the failure to develop an ahead thrown weapon for ships. The main tactical problem with depth charges was that they were necessarily launched over the stern of the ship. The fact that asdic had a minimum range of some hundreds of yards meant that charges were dropped on a target which had been invisible for anything up to the last two minutes of the approach. An ahead thrown weapon would have obviated this problem, and it is worth examining the reasons why the navy had no such weapons in 1939. The advances in attack tactics described in Chapter 6 show that the navy was well aware of the shortcomings of the asdic/depth charge combination, and to suggest, as does Van DerVat, that ‘the fact that until well into the war anti-submarine ships had to drop their charges over the stern (which meant they had to get ahead of the evading submarine’s estimated position before attacking) made killing submarines harder than the Admiralty had thought’1 is palpably unjust. Work on a weapon to overcome this difficulty started early, and in 1924 the navy was developing an ahead thrown weapon with a proposed maximum range of 1,200 yards, whose aim was to hit the submarine while still in asdic contact. Proposed tactics for this weapon were also being tested, using a 1-inch aiming rifle to simulate the bomb thrower.2 This proved unworkable as asdic was not accurate enough to give a good chance of hitting the submarine. A five-charge pattern launched over the 72 Copyright © 2003 George Franklin

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stern had an ‘area of probable serious damage’ of diameter approximately 120 yards, as shown in Figure 5. A single shell, light enough to be thrown 1,200 yards by a weapon mounted on a sloop, meanwhile, would have to be much more accurate, so demanded a precision which could not yet be supplied by asdic. Improvements in the sensor in the late 1920s suggested that the ahead thrown weapon might again become workable, and a 3.5-inch stick bomb thrower, seemingly similar to a First World War trench mortar, was fitted to HMS Torrid in 1930. Trials with a dummy bomb indicated that the 1,200yard specified range was not realistic, so this was reduced to 800 yards. Performance over the reduced range encouraged belief in the potential of the system, and stick bomb throwers were specified for the escort and patrol ships of the 1932 programme. Optimism about the weapon, however, proved to be short lived, and the throwers were removed from the specification when it emerged that the hoped-for asdic accuracies were still not being achieved. There is no evidence of any serious development work being undertaken between 1934 and 1939, but in 1939 it seems that another failed attempt was made to adapt asdic recorders to allow the launch of ahead thrown weapons.3 The work described above revolved around the launch of a single charge, but the successful wartime solutions involved launching a spread of light weapons in order to provide an enhanced lethal area. An official post-war history states that the idea of small contact fused projectiles for ahead thrown weapons ‘was advanced by A/S Experimental Establishment [the name by which the experimental wing at Portland became known] some time before 1939’,4 but no corroborating evidence has been found. One can only conclude that the navy tried to procure a heavy ahead thrown weapon, but that the sensor and weapon between them were never accurate enough to give a reasonable chance of getting the submarine inside the weapon’s lethal area. It is possible that Portland’s experimental section worked on a system that allowed a spread of lighter weapons, but even if this work did take place it produced no tangible results. The technology that enabled the production of the Hedgehog, Squid and other wartime weapons that relied on such a spread of lighter weapons was available from the mid-1930s. One can, therefore, see no real explanation for the failure to develop the weapon before the outbreak of war, and in this case the establishment and the organisation cannot escape a degree of blame. DEPTH CHARGES In the early days of the First World War depth charges had been launched singly over the stern of the carrying ship, exploding at a pre-set depth.Tactics were developed which allowed ships in line abreast to drop patterns that covered relatively wide areas, so increasing the chances of damaging the 73 Copyright © 2003 George Franklin


target. It soon became evident, however, that single ships needed to be able to lay charges with some lateral displacement, so the depth charge thrower was developed. This, essentially, was a mortar that threw the charge away from the ship’s side. A spigot with a curved metal cradle in the top was inserted into the tube of the mortar, and the depth charge, which was cylindrical in shape, was laid in the curve.At the appropriate time the throwers firing mechanism would be triggered, both spigot and charge being thrown the necessary 40 yards away on the ship’s beam in order to give the pattern lateral spread. Figure 4 shows a diagram of a thrower, and Illustration 19 shows one being loaded.

Figure 4: Depth Charge Thrower (Source: PRO ADM 189/175)

Figure 5: Standard Depth Charge Pattern (Source: PRO ADM 186/140)

The doctrine during the inter-war period was to deliver depth charges in a standard pattern of five charges in a quincunx, or centred square, as shown in Figure 5.This required precise timing on the part of the depth charge party on the quarterdeck. The team manning the rails or chutes would have to 74 Copyright © 2003 George Franklin

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drop one charge 40 yards ahead of the centre point, one at the centre point and one 40 yards after it. Meanwhile the side throwers would have to be triggered such that their charges arrived in the water, after their 40-yard flight, exactly as the second centreline charge was dropped. For a ship conducting an attack at 12 knots, which was about as slow as an attacking ship would steam, this whole process took only 12 seconds. Even the dropping of crude metal cylinders containing 300 lb of explosive, therefore, became a demanding task, and no little trouble was gone to to develop suitable equipment. The Kittiwake class pre-war escort vessels were fitted with an extra two throwers on each side to enable them to deliver seven charge attacks, but these were removed in 1938 and the five-charge attack became, once again, standard for all types of ship. From 1924 type D depth charges were used, which were fitted with a Mk 4 pistol and a Mk 5 primer.These relied heavily on wartime technology, and, although generally satisfactory, encountered some difficulties when being fired from side launchers. In the phlegmatic words of a later official history, the type D charges were ‘not as proof against firing from shock as could be desired’.5 One feels that the men on the throwers, risking as they did the explosion of 300 lb of amatol every time they launched a charge, might have been more direct in their English. No record has, however, been found of charges actually exploding either on the throwers or in the air, and in any event the pistols were modified in 1930 to take account of this shortcoming. The type D weapon was replaced in 1935 by the Mk 7, which sported, in a most unmilitary outbreak of logic, a Mk 7 primer and a Mk 7 pistol. The charge fell through the water at a constant rate of 10 feet per second, and could, immediately before launch, be set to detonate at one of six depths between 50 and 500 feet. Existing type Ds were kept in stock rather than being destroyed, and they were available in some numbers on the outbreak of war. In 1938 the Admiralty Mining Establishment at HMS Vernon, which designed all depth charges, developed a new Mk 8 pistol for use in harbours and shallow water. This was fitted to the Mk 7 charge, and allowed depth settings between 30 and 280 feet. These changes, from the type D to the Mk 7, and the subsequent introduction of the Mk 8 pistol, represented the only real advances in depth charge design between the wars, but other efforts were made to modify the weapon. In 1935, for instance, attempts were made to connect pairs of charges with lengths of wire, the theory being that if they straddled the submarine it would snag the wire, dragging the charges towards it. Tests in the mining tank at Vernon, however, showed that the wire slowed down the rate of fall of the charges too much, and tended to drag them together while falling, so having the reverse effect to that desired. It is not clear, either, how it was 75 Copyright © 2003 George Franklin


proposed to actuate the charges, which would obviously not fall any further once they had become straddled across the boat. In any event, the attempt was abandoned. Another project, undertaken in 1937, involved fixing three charges together to form a single charge which would fall faster and have a greater effect.This scheme was also abandoned in the experimental stage, for reasons which remain obscure. This was a shame as, during the war, it was found that, in order to give a coverage in depth as well as in plan, it was necessary to drop two five-pattern charges at the same time, one consisting of heavier charges which would fall faster.This ten-charge pattern thus produced two simultaneous sets of explosions at different depths and proved extremely effective, if costly in charges. Evidently, if the 1937 experiments had been pursued, this tactic might have been available at the outbreak of the war. Amatol, which was the standard explosive compound used for depth charges up until the early 1930s, broke down if stored for a protracted period in a hot climate, so, for the Far East, depth charges containing TNT were substituted.6

Figure 6: Depth Charge Chute (Source: PRO ADM 189/176)

The business of discharging the weapons over the stern of the ship also received attention in the inter-war years.There were two devices that could be used to launch charges over the stern: the chute or the rail. The former was a small ramp with a curved housing at the top in which the charge was stowed, as shown in Figure 6. When in harbour or away from a submarine menace, the charge, if it was loaded in the chute at all, was held firm by a main strop over the top as well as harbour lashings fixed to each end.When it became possible that the charge might have to be released, the harbour lashings were removed and, when the time came to release the charge, a quick-release mechanism on the main strop was triggered and the charge rolled over the stern.Although it was simple and extremely reliable, the main 76 Copyright © 2003 George Franklin

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disadvantage of the chute was that it held only one charge, so had to be reloaded after each attack. The explosive alone weighed 300 lb, and when the metal case and actioning mechanisms are taken into account it will be appreciated that a depth charge was not an easy thing to handle on a pitching and rolling deck.The standard reload time of three minutes for a full pattern of five charges became virtually impossible for chutes, especially in heavy weather, so another device was clearly required.The solution, which appeared during the First World War but was still by no means universal in 1939, was the rail (see Figure 7).This consisted of a pair of mild steel angles on which up to 12 charges could be placed ready to roll over the stern of the ship one at a time.A system of stops and bars prevented more than one being discharged at a time, and a number of attacks could be executed without the rails having to be reloaded at all. A second pair of rails ran over the top of the charges to prevent them from escaping in a heavy sea, and the equipment overall was a good deal bigger and heavier than were the chutes. The rails also suffered from the disadvantage that they sometimes became distorted by the impact of the charges either when the ship rolled or during loading, and a distorted rail could prevent the release of charges, with potentially serious results. Overall, though, rails were found to be far more satisfactory than chutes, and by 1939 the only vessels routinely fitted with chutes were battleship picket boats, fast motor A/S boats and early escorts.

Figure 7: Depth Charge Rail (Source: PRO ADM 189/176)

The sketch designs for the convoy sloops of the 1933 programme, which became the Enchantress or Bittern class, show them being fitted with two depth charge chutes aft and one thrower on each side. The chutes were supplied with 12 charges each, and the throwers with eight each.This would allow for eight full five-charge patterns to be dropped, but the fact that the ship was fitted with only two chutes, and a five-charge pattern demanded 77 Copyright © 2003 George Franklin


the release of three charges over the stern, meant that there was a requirement to reload one of the chutes between the release of the first and last charges. As stated earlier, a ship running at 12 knots would have to drop the pattern in 12 seconds, and it was clearly not realistic to try to reload the chute in that time, so a ship fitted with only two chutes could not lay a five-charge pattern. It is not evident when this shortcoming was put right, but by the time the war started the ships had been fitted with a third chute aft.The use of chutes, rather than rails, however, still meant that a fast reload was required between attacks, and it is for this reason that rails were fitted to all subsequent designs. It is worth pointing out here that, when the huge number of vessels which had been taken up for A/S duties during the First World War were paid off, sufficient presence of mind was shown not to scrap the rails and chutes with which they had been fitted when requisitioned. The result was that in 1939 there were large numbers of chutes and rails available to be fitted to newly built vessels and those being taken up from commercial owners. In the early years the men on the quarterdeck, known as the depth charge party, would start to drop a pattern following a verbal order from the bridge, the depth charge officer using a stopwatch to determine the release time for the different charges. This was modified during the First World War, when some ships were fitted with remote control that allowed the bridge personnel to release the charges. Difficulties were encountered with this system, primarily because the hydraulic pipes linking the bridge controls to the release gear were too thin, making the movement of the controls very hard work. This problem, however, had been overcome by the late 1920s, and bridge firing became standard on some classes of ship. For those ships which did not benefit from remote firing, or for those occasions when the remote firing mechanism failed, a buzzer was introduced that could be sounded from the bridge, ordering the depth charge party to release the charges locally. Ships were then fitted with a ‘ready’ light which enabled the depth charge officer to indicate to the bridge when the next pattern was loaded and ready to be fired. The final stage in automation came with the introduction of an automatic clock to time the release of the charges. It is not clear how the clock actuated the release of the charges, but it could evidently be set for the correct speed, and once started would ensure that the pattern laid was as accurate as possible.This obviated the need for a harassed depth charge officer, on a wet, windswept and quite possibly dark deck to work to half-second accuracies from a stopwatch. It was accepted that it was unlikely that the first attack on a submarine would be successful, so the necessity to reload throwers and chutes was a factor which needed to be considered. An attempt was made to speed the reloading of chutes by arranging for them to swing inboard for loading, but it was found difficult to integrate the hydraulic remote control link into this swinging chute, and the idea was abandoned. Clearly the replacement of chutes with rails answered some of the problems, but it remained difficult to load 78 Copyright © 2003 George Franklin

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the throwers within the standard time. It was suggested in 1925 that in newly built ships the throwers could be recessed so that the top of the thrower was flush with the deck, thus making the reloading very much easier. The uncompromising reply was that the standard time was perfectly achievable with the throwers where they were.At a Portland conference in 1938, however, it was decided that the interval between attacks would be longer than had previously been thought, so the standard reload time was increased to five minutes, and some of the rush was thus taken away from the reloading process. The final point concerning the arrangement of equipment on the quarterdeck revolves around the danger presented by the presence of the charges themselves. At the 1938 conference mentioned above it was pointed out that the presence of the charges on the open deck could pose a safety hazard. At the best of times the presence of 40 300-pound amatol charges on the quarterdeck must have been worrying, and the prospect of one being detonated during an air attack was held up as an unacceptable risk. It was actually proposed at the conference that all charges should be jettisoned if an air attack seemed likely, but it was pointed out that this would render the ships utterly useless for the rest of a voyage. A compromise was reached which involved the provision of bulletproof steel covers for the areas where the charges were stowed, but photographic evidence of wartime and prewar ships indicated that this never actually happened. The depth charge allowance per ship was set in 1938 at 30 for an asdicfitted destroyer, 40 for escort or patrol vessels, 25 for trawlers and 15 for the Table 4: Depth Charge Armaments, 1939

Source: PRO ADM 189/175, Technical History of A/S Weapons.

various other craft that might be used in an A/S role. At that time the navy held a reserve of 25 per cent over the fleet allowance outlined above, but was manufacturing another 6,000 which were to be ready by the end of the financial year 1937–38.The Admiralty and the supply committees were also considering a programme for procurement of a further 6,000 over the following three years, which, as well as providing the weapons themselves, would ensure the maintenance of production capacity. 79 Copyright © 2003 George Franklin


AIR WEAPONS In parallel to the Trenchard-Keyes agreement governing naval aircraft and their crews, which is discussed in Chapter 5, an agreement was reached in 1925 that laid down the way that air weapons would be specified and produced. The Admiralty would specify the performance required but the Air Ministry would be wholly responsible for design and production, and an annual conference would apportion costs. Torpedoes, which were not anti-submarine weapons so do not concern us, remained an entirely naval responsibility.The reader will quickly see that such an agreement meant that design failures could not readily be laid at the door of any one department. Unless the highest levels of co-operation existed between the concerned departments of the two constantly warring ministries, the development of entirely new weapons would be extremely difficult. Add to these factors the belief held throughout the air force, and presumably within their research and development laboratories, that naval air support was a sideshow to the strategic attack, and one can see that the procurement of air-launched A/S weapons was never destined to be a strong area. The early inter-war years saw some acrimonious correspondence between the Admiralty and the Air Ministry, the former accusing the latter of dragging their heels in the development of air-launched weapons. After repeated prompting, the Air Ministry stated in 1920 that a bomb would be developed with the option of an instantaneous impact fuse for a submarine on the surface or a tail impeller delay fuse for a dived target.7 The Director of the Tactical Division suggested that a single bomb might be developed with a combined fuse. In November 1922 the Air Ministry acceded to this request, but at the bomb conference of 1923 there was no mention at all of antisubmarine weapons. At the 1924 bomb conference it was decided that 250-lb and 500-lb light case bombs should be developed for anti-submarine attack. The following year there was a debate between the Admiralty, who favoured the increased probability of a hit given by a stick of 100-lb bombs, and the Air Ministry, who believed the killing power of a single 500-lb was more useful. The Admiralty appear to have won this argument, but progress was slow. Draft specifications were ready by May 1928, trials started in September 1930 and the first bombs were introduced in March 1931. It was, however, not until 1934 that the Royal Armaments Establishment began to investigate underwater explosions.8 The light case A/S bomb could be adjusted to detonate at a pre-set depth, but this adjustment could only be made when the aircraft was on the ground. Attempts to enable the aircrew to re-set the detonation depth while the aircraft was in the air failed, and in 1929 it was reported that the bomb would explode either on hitting the submarine, or, failing that, when it reached the pre-set depth.9 By 1930 an impeller fuse on the front of the 80 Copyright © 2003 George Franklin

1.

Bridge repeaters and asdic communications on a destroyer, c. 1932.The equipment was not controlled from this position, but the range readout, distance indicator and speaker over which the ‘pings’ could be heard greatly facilitated the attack. (Source: Public Record Office, PRO ADM 186/495)


2.

A 1922 photograph of HMS Rocket’s asdic control position, showing the training wheel and the voice pipe to the bridge. Despite the quality of the chair, this cannot have been a pleasant post in a running sea. (Source: Public Record Office, PRO ADM 186/758)


3.

A First World War hydrophone operator training the equipment to obtain the bearing of a contact. This equipment represented the stage of the technology in 1919. (Source: Imperial War Museum, IWM SP 479)

4.

HMS Rocket’s transducer, showing proud of the bottom of the hull. Note also the nonstreamlined, semi-circular-type dome, removed for access. (Source: Public Record Office, PRO ADM 186/758)


5.

Retractable streamlined dome for type 121 asdic, showing the improvement achieved over the nine years since the type 114 (illustration 4) was in production. (Source: Public Record Office, PRO ADM 186/495)


6.

Basic, and appallingly exposed, asdic control position on a trawler. The operator would train the equipment using the small wheel, and the master would shout conning orders down to the wheelhouse. (Source: Public Record Office, PRO ADM 186/495)


7.

A Sa Ro London small flying boat, stalwart of many inter-war exercises. (Source: Imperial War Museum, IWM HU 3173)

8.

Pre-war Avro Ansons flying in formation (Source: Imperial War Museum, IWM HU 68327)


9.

Two A/S bombs fitted to a Sa Ro London, showing the nose impeller arming device. (Source: Imperial War Museum, IWM HU 3171)

10. Short Sunderland flying boat, ultimately successful inter-war design which did good war service. (Source: Imperial War Museum, IWM HU 3177)


11. Marshal of the Royal Air Force Lord Trenchard. Like Harris, he was a capable and patriotic man, who was sure that he was working for the national good. Their uncompromising pursuit of the bomber offensive, however, probably did as much harm to Britain’s anti-submarine capability as any other single factor. (Source: Imperial War Museum, IWM BM 21045)

12. Marshal of the Royal Air Force Sir Arthur Harris. (Source: Imperial War Museum, IWM HU 88537)


13. Admiral of the Fleet Lord Chatfield, who as First Sea Lord from 1933 to 1938 did so much to prepare the navy for war. (Source: Imperial War Museum, IWM MH 9723)

14. A famous wartime photograph of Captain ‘Jonny’Walker. Although he rose to fame after 1939, during the inter-war years he was typical of unappreciated and under-promoted anti-submarine specialists. (Source: Imperial War Museum, IWM A 21988)


15. A poor air shot of HMS Stork, which nevertheless shows the layout of the depth charge equipment around the quarterdeck. (Source: Imperial War Museum, IWM FL 9939)

16. Port quarter of HMS Ibis, showing depth charge equipment, again including the wartime fit of side launchers. (Source: Imperial War Museum, IWM FL 10455)


17. HMS Enchantress, built as an anti-submarine vessel but employed before the war variously as a survey vessel and an Admiral’s yacht. The after-deck housing was removed and replaced with depth charge equipment as war approached. (Source: Imperial War Museum, IWM FL 11395)

18. Starboard quarter of HMS Stork, showing the two depth charge rails and the side depth charge launchers. Being a wartime photograph, this shows two side launchers, rather than the pre-war fit of only one. (Source: Imperial War Museum, IWM FL 12999)


19. Loading a depth charge thrower. Two such throwers had to be loaded between attacks, during which time the ship was likely to be manoeuvring violently.The standard reload time was three minutes. (Source: Imperial War Museum, IWM A 4571)

20. A depth charge in the air, having been fired from its thrower. (Source: Imperial War Museum, IWM A 3571)


21. Detonation of a single depth charge. Simultaneous detonation of five such charges must have been an impressive sight. (Source: Imperial War Museum, IWM A 4570) Copyright © 2003 George Franklin

22. Anti-submarine nets during the Seawolf trials.The right-hand net clearly shows where the submarine has hit it, and between the nets the indicator buoy towed by the submarine during exercises can just be made out. (Source: Public Record Office, PRO ADM 244/17)


23. The luckless HMS Seawolf on the surface after having become entangled during indicator net trials. Note that the riding wire from the top of the periscope sheath to the fo’c’sle appears to have given. (Source: Public Record Office, PRO ADM 244/17)


24. Heavy anti-submarine nets being laid near Rosyth for the Seawolf trials. Laying nets was no quick process, and from this photograph it can be appreciated why their recovery was described as being an ‘arduous and time-consuming’ job. (Source: Public Record Office, PRO ADM 244/12)


WEAPONS

A/S bomb had been developed which prevented the bomb from arming before it had fallen a safe distance from the aircraft. This fuse only turned when in flight through the air, and was designed to protect the aircraft from self-destruction in the unusually low bombing runs that it was thought would be used for A/S work.10 These arming vanes were evidently either abandoned, or ineffective, as there are widespread reports of the wartime weapons being as dangerous for the aircraft as they were for the submarines, and there was at least one instance of a naval aircraft being destroyed by its own bombs.11 It is possible that bombs bounced off the sea surface, so travelling through the air and arming themselves, while still staying dangerously close to the aircraft. A good deal of relevant experimental work was clearly being undertaken at this time, as records survive of other trials taking place in 1936. These included analysis of the stability in flight and angle of entry into the water of A/S bombs,12 as well as their behaviour once they entered the water. One such report concluded that ‘for entry velocities of more than 250fps the trajectory curvature may be so great that accurate bombing of submarines at depths greater than 50ft would be impossible’.13 Pursuant to this problem, experiments were carried out at the Royal Aircraft Establishment, Farnborough, in 1936, which involved arranging for the bomb to spin in flight like a bullet or shell. Having steadily increased the spin rate to some 14,000 rpm, achieved by firing the bomb out of a rifled barrel, the scientists concluded that this method was ineffective.14 It is unclear who ordered the investigation into a means of scoring a direct hit on a submerged submarine, but the difficulty of locating such a target, and the fact that even after the outbreak of war it was still nearly impossible to hit a surfaced boat, imply that little informed thought had gone into the preparation of the specification. Trials were also being conducted into the underwater detonation of 250-lb and 500-lb A/S bombs filled with both amatol and baratol. Despite, or perhaps because of, the trials and experiments described above, little actual progress was achieved, and in the late 1930s Britain still lacked an effective anti-submarine bomb. By April 1939, however, things had begun to move, and Sir Kingsley Wood, Secretary of State for Air, was able to report to the CID that ‘orders for fuzes for anti-submarine bombs had been placed’.15 Development clearly progressed even then at a sedate pace. Two months into the war we find the Deputy Director of Research and Development at the Air Ministry exchanging correspondence with the Royal Aircraft Establishment at Farnborough about whether or not the fuses in the tails of A/S bombs were ripped off as they entered the water.16 A month later an unnamed official in the Air Ministry noted, no doubt to the great comfort of the Admiralty, that ‘the whole policy of anti-submarine bombing has recently been the subject of extensive discussion’.17 Ironically, one of the few ideas for a weapon that might work was suggested by an aircraft manufacturer and dismissed out of hand by the Air 81 Copyright © 2003 George Franklin


Staff. When Shorts were getting into trouble with the eventually cancelled Sarafand flying boat programme, they suggested that downward-firing 10lb guns could be fitted to the enormous aircraft to increase its offensive capability.The guns would be capable of firing for a period of 15 seconds as the aircraft overflew its target, and the possibility of using them to attack surfaced submarines was specifically mentioned.The Air Ministry dismissed the idea and criticised the design team for embarking on such fanciful schemes. The Deputy Chief of the Air Staff wrote to the Air Member for Research and Development: I do not suppose that you want me to spend a lot of time on this matter… I suppose we must not discourage them from trying to think for themselves. It [the gun scheme] clearly arises from the efforts of the firm to find a use for their ‘Sarafand’ type flying boat.18 While such a weapon would have been entirely useless, and dangerous to use, against armoured and defended surface ships, it is difficult not to speculate on its use against a relatively vulnerable and lightly gunned submarine. Another idea for an air-launched weapon was a proximity-fused bomb, which would be actuated, as it sank, by the electromagnetic signature of a U-boat.This was first mooted in the mid-1930s, but appears to have received little attention. It is next mentioned in a letter from the Admiralty to the Air Ministry in 1939 in which the latter department was ‘reminded’ of the tactical requirement for a proximity fuse. Further investigation led to the Air Ministry abandoning the idea as impractical in March 1940.19 In the event, wartime experience showed that air-launched depth charges were far more effective than bombs. There was certainly some awareness during the inter-war period that air-launched depth charges might be useful—an article in a 1929 RUSI Journal, for instance, stating that ‘for aircraft the depth charge is the sole weapon’.20 In his comments on exercise RW in 1933, the Commanding Officer of HMS Glorious stated that there was an urgent need for air-launched depth charges, and was backed up in this by his Commander-in-Chief.This was in the wake of an anti-submarine exercise during which aircraft from HMS Glorious had detected many of the attacking submarines, both at periscope depth and dived, but had been unable to take action against them.21 No evidence has, however, been found of any great will in either the Admiralty or the Air Ministry to develop air-launched depth charges. It is entirely evident from contemporary papers that, until the eve of war, the Air Ministry gave little or no consideration to the tactical question of how to attack a submarine. In May 1939, the CO of 16 Group requested the production and issue of cards showing the flag hoists used by hunting ships so that aircrew could contribute to the hunt,22 and, seemingly without irony or self-consciousness, an Air Ministry paper of July 1939 told the 82 Copyright © 2003 George Franklin

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reader that ‘the bombing of submarines demands great skill…it requires great practice’.23 It is evident that the Admiralty was aware of the general deficiency in airborne A/S, the Director of the Naval Air Division writing in January 1939: ‘that the anti-submarine air forces, both of the FAA and the RAF, are untrained and their methods undeveloped are facts which have been strongly represented by DNAD’.24 Under the pressure of war, work did accelerate, and in October of 1939 one finds the RAF beginning to consider the problem of how to hit a visible submerged submarine. An Air Ministry paper written in November 1939 suggested that experiments be carried out to determine the best height at which an aircraft should patrol in order to see a submarine without itself being seen.25 This is particularly odd as a 1938 Tactical Division memorandum, which was circulated widely within the RAF, specified that ‘a height of about 1500ft is the best from which to sight submarines, and at this height aircraft are not normally heard at as great a range as when they are flying higher’.26 In November 1939 Coastal Command had got as far as proposing a method of sighting anti-submarine bombs. December found them discussing whether to attack across or along the line of advance of a submarine,27 and holding a conference to discuss the clearly entirely unexpected ‘urgent requirement’ for a ‘low height sight for Anti-Submarine bombing’. As an extension of this conference a delegation went to Pembroke Docks in January 1940 to look at the possibility of fitting a sight to a Sunderland. They discovered, once again to their evident surprise, that the pilot’s position was so arranged that he could not see the target during his approach. After 20 years of preparation and five months of war, Coastal Command reached the astonishing conclusion that the Sunderland pilot would be advised to approach the submarine with his head sticking out of the side window.28 This author is unconvinced by the explanation that all RAF officers were congenital idiots, so a more satisfactory reason for this patent failure must be sought. As will be discussed in Chapter 6, much of the value of an aircraft in the A/S role was as a deterrent and a reconnaissance asset. Flying ahead of a force they could, by their presence alone, force submariners to dive, so blinding the submariner and affording protection to the surface ships. If the aircraft saw the submarine before it dived then A/S vessels could be called to the scene, and they could hunt the submarine. An aircraft in such a role would have no need of a weapon. When operating on patrol, however, and not supported by naval forces, the story would be a very different one. In these circumstances the aircraft could, by forcing the submariner to dive, reduce his visibility, slow him down and interfere with his battery charging. This, though, was of little more than nuisance value against a passaging submarine, and without an effective weapon the unsupported patrolling aircraft was of very little use. It seems unlikely that peacetime exercises were conducted in unsupported air operations against submarines. Submarines were such a rare commodity 83 Copyright © 2003 George Franklin


that, when one became available for an exercise, the navy would have wanted to maximise the benefit by involving surface ships as well. Further, RAF enthusiasm for A/S was rarely if ever so great that they would, on their own initiative, plan exercises in the unsupported use of aircraft. Certainly, throughout the research for this book no evidence has been found that aircraft ever exercised against submarines without a surface attack or escort force also taking part. While such negative evidence is far from conclusive, it does seem reasonable, given the number of A/S exercise records that have been uncovered, to argue that such practices probably did not take place. One thus arrives at a position where, by 1939, Coastal Command had only ever practised A/S operations in direct protection of a surface force, or patrol operations with the support of a surface element. Such exercises would have taught the aircrew that, when they found a submarine, all they had to do was force it to dive and then mark its position for the benefit of the surface forces. Given the antiquity of the equipment that they were forced to use, this mission alone proved hard enough, and they would hardly have wanted to make their own work harder by bidding to attack the submarine as well. This state of affairs would explain the following comment, which emanated from the Air Ministry in late 1939: ‘The A/S bomb can be considered, at best, only a weapon to keep submarines below periscope depth, as the possibility of making a surprise attack and finding the submarine on the surface is very small.’29 This implied that the A/S bomb was not a weapon that was worth pursuing. This situation may have been exacerbated by the tactical doctrine which dominated inter-war thinking about A/S operations in home waters. Broadly, if the enemy chose to conduct an unrestricted submarine campaign, merchant traffic around the UK would be put into convoy, and if he opted for a restricted campaign, convoy would not be adopted. In the former case, air assets would be used in direct support of the convoys, most of which would be escorted; and, in the latter case, home waters would be divided into sectors to be patrolled by combined air/sea A/S striking forces. In both circumstances, then, the aircraft would function only as a surveillance asset, and surface ships would conduct the attack.Thus the conviction that aircraft were reconnaissance assets which, invariably acting in support of surface ships, would not require weapons was further strengthened. Undoubtedly the situation was worsened still by the prevalence of the bombing faction within the RAF and the Air Ministry. Such was the drive to direct spending and industrial resources towards Bomber Command that it would have required a sustained effort on the part of Coastal Command, probably backed by the Admiralty, to divert meaningful resources towards the development of A/S weapons. Given the factors outlined above, it is hardly surprising that such an effort failed to develop until the realities of war began to erode Bomber Command’s virtual monopoly. One finds, therefore, that what initially appears to be a crass, almost 84 Copyright © 2003 George Franklin

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culpable, oversight on the part of the Air Ministry in failing to develop air weapons, in fact followed naturally from combined Air Ministry and Admiralty policy. The tragedy was that in the initial months of the war the ratio of A/S aircraft to A/S vessels was higher than had been expected, so the aircraft often found themselves on unsupported patrols over the North Sea, during which any number of opportunities to damage or sink detected U-boats were lost through the lack of an effective weapon system. In 1939 Coastal Command reported 51 attacks on U-boats, the vast majority of which were carried out independently, and none of which appear to have resulted in serious damage to the boats. On 30 January 1940, a Sunderland of 228 Squadron, acting in concert with HMS Fowey and HMS Whitshed, scored Coastal Command’s first A/S success, sinking U-55. Ironically, the first successful independent action by RAF aircraft against a U-boat was brought not by Coastal Command but by a group of Bomber Command aircraft on an armed reconnaissance, which sank U-31 in Schillig Roads using conventional impact-fused bombs.30 The Admiralty was, by early 1940, becoming conscious of the waste of resources involved in unsupported air patrols, and A/S striking forces, based on trawlers, started to appear in the North Sea, where they conducted patrols co-ordinated with Coastal Command aircraft. That the lack of an effective air-launched A/S weapon derived from a combined Air Ministry and Admiralty misconception of the way aircraft would be used in war, is admittedly a thesis based largely on speculation. Previous studies by Roskill,Terraine, Padfield and others have told the story without attempting an explanation,31 while others have described the 1939 situation without studying the pre-war process.32 The simplest explanation would be that the involved departments were staffed by people who were too stupid, lazy or generally stoneheaded to progress the scheme, but, as mentioned in the Introduction, that is rarely a satisfactory explanation. Simple obstructiveness by the bombing lobby, who were after all acting in what they believed to be the best interests of the nation, goes further. It does, however, seem likely that the misapprehension of wartime conditions and the failure to practise independent air A/S operations exacerbated the situation. While a good deal of blame can be laid at the door of the Air Ministry, it was clearly not their fault that there were so few surface escorts available that aircraft were forced to carry out independent operations for which they were neither equipped nor trained. NOTES 1 2

Dan Van Der Vat, The Atlantic Campaign: The Great Struggle at Sea 1939–1945, Hodder & Stoughton, London, 1988, p. 116. PRO ADM 186/444, CB 3002 (24).


BRITAIN’S ANTI-SUBMARINE CAPABILITY, 1919–1939 3 Willem Hackmann, Seek and Strike: Sonar and the Royal Navy 1914–1954, John Murray, London, 1995, p. 187. 4 PRO ADM 189/175, Technical History of A/S Weapons. 5 Ibid., p. 41. 6 PRO CAB 16/109, minutes of the 5th meeting of the DRC, 19 Jan. 1934. 7 PRO ADM 116/2089, Aircraft Bombs and Torpedoes: Conferences with the Air Ministry. 8 CHURCH ROSK 14/4. 9 PRO ADM 186/476, CB 3002 (29), p. 36. 10 PRO AVIA 6/1825, Design of Arming Vanes for A/S Bombs, 1930. 11 Two Blackburn Skuas attacking U-30 on 14 Sept. 1939. See Chapter 7. 12 PRO AVIA 18/1219, Ballistics of A/S Bombs Fitted with Ballistic Caps, Trial reports dated Feb. 1936 and Sept. to Dec. 1937. 13 PRO AVIA 6/3396, RAE Experiments with A/S Bomb Models, July 1935, and AVIA 6/ 3375, Further Experiments with A/S Bomb Models, Dec. 1935. 14 PRO AVIA 6/11959, Tests of A/S Bomb Model with Spin, Feb. 1936. 15 PRO CAB 2/8, 354th meeting of the CID, 27 Apr. 1939, p. 6 of the minutes. 16 PRO AVIA 15/95, A/S Bombs: Technical Policy, Letter dated 9 Nov. 1939. 17 PRO AVIA 15/95, A/S Bombs: Technical Policy, Minute dated 21 Dec. 1939. 18 PRO AIR 2/1657, Use of Flying Boats as Offensive Weapons, DCAS to AMRD, 16 Nov. 1935. 19 PRO AVIA 13/739, Proximity Fuze for A/S Bombs. 20 Lt. Cdr D.G.Wemyss, ‘The Submarine and its Antidotes Today’, RUSI Journal, May 1929. 21 PRO ADM 186/154, CB 1769/33 (2). 22 PRO AIR 15/38, Air Tactics, A/S Operations, Note by CO 16 Gp, 12 May 1939. 23 PRO AIR 14/279, A/S Tactics, Coastal Command paper dated 1 July 1939. 24 PRO ADM 1/12141, Anti-Submarine Striking Forces, Memorandum by DNAD dated 17 Jan. 1939. 25 PRO AIR 15/63, Air Operations, Policy, August 1939. 26 PRO ADM 1/12141, Anti-Submarine Striking Forces, Memorandum written by Capt. Budgen, D of TD, dated 13 Apr. 1938. 27 Ibid. 28 The above developments are all recounted in PRO AVIA 15/70, Aiming of A/S Bombs. 29 PRO AVIA 15/95, A /S Bombs: Technical Policy, Minute by RD Adm 4 (no name supplied), dated 1 Nov. 1939. 30 Stephen Roskill, The War at Sea, HMSO, London, 1956, Vol. 1, p. 132; Kenneth Wynn, U-Boat Operations of the Second World War, 2 vols, Chatham Publishing, London, 1997, Vol. 1, p. 22. 31 Roskill, War at Sea, Vol. 1, pp. 135–6; John Terraine, Business in Great Waters: The Uboat Wars 1916–1945, Leo Cooper, London, 1989, p. 248; Peter Padfield, War Beneath the Sea: Submarine Conflict 1939–1945, John Murray, London, 1995, p. 73; John Buckley, Constant Endeavour: The RAF and Trade Defence 1919–1945, Keele University Press, Keele, 1995, pp. 166–8. 32 Henry Probert, ‘Allied Land Based Anti-Submarine Warfare’, in Stephen Howarth and Derek Law (eds), The Battle of the Atlantic 1939–1945: The Fiftieth Anniversary International Naval Conference, Greenhill Books, London, 1994, pp. 374–5; Corelli Barnett, Engage the Enemy More Closely, Hodder & Stoughton, London, 1991, pp. 586–8.


5

Platforms

Reflecting the Mahanian division of tasks between the battle fleet and the control fleet, the policy between the wars was for A/S protection of naval forces to be provided by destroyers, while trade protection would be provided by specially constructed convoy sloops or escort vessels, augmented by old destroyers. Patrol of coastal areas, choke points and harbour approaches would meanwhile be carried out by smaller patrol vessels or converted trawlers. Submarines, unsuitable as they were for operations which required integration with other units, would be used for forward A/S patrol, specifically in the approaches to enemy submarine bases. Land-based aircraft and flying boats, which came within the Air Ministry’s domain, would be used for escort or area patrol within the narrow waters around the UK, while Fleet Air Arm carrier-borne aircraft would enhance the protection provided to naval forces. Initially, the requirement was to provide destroyers and aircraft to support the defence of the eastern Empire, though the emphasis later moved to survival of the anticipated German attempt at a knockout blow.Trade defence and patrol vessels, which would be more important for the subsequent long war than for the knockout blow, would not be built in large numbers in peacetime. Instead, a few of each type would be built so that designs and operating procedures could be perfected. Industrial capacity, meanwhile, would be reserved to allow for rapid wartime procurement of sufficient vessels to protect maritime trade during the long economic war which would favour the British Empire. In this chapter we will ask how faithfully actual procurement followed these policies, and we will trace the histories of the most important ship and aircraft procurement programmes. DESTROYERS The genesis of the great destroyer building programmes can be seen in proposals made by the Admiralty in 1923. These held that Britain should



start building in quantity, so as to achieve parity with Japan and the United States by the end of the period covered by the ten-year rule.The argument was that, by 1929, 87 of Britain’s 207 destroyers would be at their age limit, as against none of Japan’s 91 and 23 of the US Navy’s 295.Thus Britain was facing a situation in which it would have only 120 useful destroyers, as against the 91 owned by Japan and the 272 of the US Navy. The proposal was to build two flotillas, each of eight ships and a leader, every year from 1927 to 1931, and thereafter to build one such flotilla every year.1 The First Lord, the Rt Hon. Leopold Amery, seems to have obtained the Chancellor’s verbal assent in January 1924, but following the collapse of the Baldwin government and MacDonald’s institution as the first Labour Prime Minister the whole construction programme, like the Singapore Base scheme, was thrown into doubt. The subsequent return to power of a Baldwin government restarted the process, and in July 1925 the Admiralty announced a reduced programme, including the construction of one flotilla of destroyers per year from 1927 to 1930.2 At this time the policy was to build alternate flotillas with either asdic or minesweeping gear. In a 1931 paper the Director of the Tactical Division argued that for a Far East war a total of seven asdic and six minesweeping flotillas was needed.3 In the event of a European war, however, and here it must be remembered that Hitler had not yet come to power, a total of seven asdic-fitted flotillas would still be required. Indeed, the papers stated that It will be seen that a total of 117 destroyers will be quite insufficient in the case of a European war; particularly in view of the large numbers of submarines likely to be employed against us…a war in which attack on British lines of communications by submarine is likely to prove a primary liability.4 Before hailing the author of this report as a visionary when all others were steadfastly ignoring the possibility that trade routed to the UK might suffer submarine attack, it must be remembered that he was in the process of arguing for an increase in the number of destroyers, and an expensive change in the asdic-fitting policy. In this light it is hardly surprising that he painted the home waters’ submarine threat larger than it perhaps really was. The famous destroyers of the inter-war years—from the ‘A’s of the 1929 and 1930 programmes to the ‘K’s of the 1938 and 1939 programmes— enjoyed great wartime success, and have had commensurate numbers of books written about them. Repetition of their characteristics would achieve little here, so they will not be discussed at any great length. It should suffice to say that they were capable platforms, with asdic being fitted in build from the ‘B’s onwards.They had high maximum speeds, were well provided with depth charge equipment and carried sufficient manpower to operate asdic 24 hours per day for long periods. Although it was envisaged in the pre-war plans that they would be used almost exclusively for work with the 88 Copyright © 2003 George Franklin

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fleets, the realities of war meant that they were employed early in trade defence, where they acquitted themselves well.5 The earlier ‘V’ and ‘W’ class destroyers, mostly completed soon after the First World War, fall into something of a middle ground as far as classification is concerned.They were clearly destroyers when built, and continued to be so through the majority of the inter-war years. Although some were not fitted with asdic until the late 1930s, they were employed in a large number of anti-submarine exercises, either in visual screens, or to ‘simulate’ asdicfitted vessels. As they became older, however, and were judged unsuitable for work as fleet destroyers, they started to be converted for the escort role, being fitted with anti-aircraft guns and asdic. To this end, it was decided in 1937 that ‘destroyers rearmed with HA/LA [high angle/low angle] guns and equipped with asdics will, in future, be called “Escort Vessels”’.6 In large organisations, however, such semantic changes take time to sink in, and they continued to be referred to as destroyers right through the war. By the time war broke out, three had been converted to the escort role and another three were nearing completion, while a further nine were converted during the course of the war.7 In early 1938, with the storm clouds visibly gathering, the Director of the Tactical Division reckoned up the forces that would be required for war, and balanced his results against the assets that were actually available. The issue of fleet protection was somewhat glossed over with a statement that the destroyer requirement would depend on the fleet strength in the theatre of war, but trade defence was addressed more systematically. He estimated that 100 ocean-going escort vessels would be needed for convoy protection, and implicit in the terms of the paper was an acceptance that no modern destroyers were to be included in this figure. This meant that the 100 required would have to be found from among the 36 ‘over age’ ‘V’ and ‘W’ class destroyers and the various pre-1932 sloops that were being fitted with asdic. In addition to these there were newly built patrol and escort vessels of the Bittern, Kingfisher and Egret classes available in 1938, with a further three planned under the 1937 programme.The shortfall, the paper stated, might have to be made up from trawlers and patrol vessels which were entirely unsuitable for the escort role, but would have to do. The situation, however, would improve as ships built in wartime became available. SLOOPS AND ESCORTS During the First World War the vast majority of the Royal Navy’s antisubmarine craft were small sloops or trawlers, most of which spent their time conducting ineffective anti-U-boat patrols in home waters. Clearly, the postwar introduction of asdic and the acceptance that convoy would almost certainly be used in a future war changed the specifications of anti-submarine 89 Copyright © 2003 George Franklin


vessels, but nonetheless it was accepted that small, simple and cheap ships would have their place in any anti-submarine campaign.As Fisher is supposed to have said, for these purposes the navy needed vessels that ‘will last six months and can be driven by the man in the street’.8 Such vessels, quickly built in civilian yards and manned by reservists, were not needed in any quantity during peacetime, so Admiralty policy in the inter-war years was not to produce large numbers, but to build one or two prototypes of each class, so as to be ready to build them in bulk should the need arise. This section, therefore, tells a story not of mass production, but of an Admiralty which sought to provide workable designs and production capacity for ships which could be built and sent to sea in war or emergency. One of the earliest overt expressions of this policy came from RearAdmiral Roger Backhouse who, as Controller, wrote in 1932 that, From the point of view of being ready for quick production in an emergency, it would be of great advantage to have one vessel of each type built and standardised, if possible, so that all drawings and details would be ready, which would not only save probably two months, but should ensure the vessels on completion being satisfactory for the service intended.9 Patrol sloops were produced from 1927 to 1930, but were actually designed primarily as minesweepers rather than as A/S vessels. Policy at the time held that, in order to avoid hitting moored mines during sweeping operations, minesweepers should have a draught of no more than eight feet. A/S vessels, on the other hand, were considered not to be properly effective if their draught was less than eight feet, as a shallower draught would reduce asdic effectiveness, the transducer performing much better if out of the mixed upper layer of the sea. Any attempt to combine anti-submarine and minesweeping capabilities in one vessel were thus bound to be fraught with difficulties.The Director of the Signal Division, in his capacity as a technical advisor on the development of asdic, suggested in 1936 that it might be possible to arrange for a retractable dome to extend some way beneath the hull of a minesweeper, but there is no evidence of this idea having been progressed. Although there were various attempts to design a combined minesweeper and A/S vessel, this basic conflict meant that no such ship would ever be fully satisfactory, and more specifically it meant that the 1927– 30 sloops were not suitable for A/S work. The Director of Torpedoes and Mining, whose responsibility included minesweeping, suggested in 1936 that, if there were sufficient A/S vessels patrolling around the UK, the U-boats would never be able to approach the coast to lay mines.10 This idea, born either of massive hopefulness or a true ignorance of the limitations of A/S equipment, fortunately seems not to have driven any subsequent policy decisions. 90 Copyright © 2003 George Franklin

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In the event, minesweepers in the late 1930s were built with space for asdic equipment, but fitting of the equipment did not actually start until the pre-war emergency assumed dire dimensions. These ships, in today’s parlance ‘fitted for but not with’, performed better than expected in their secondary A/S role, and in Chapter 7 we will come across one, HMS Gleaner, actually sinking a U-boat. As there was undoubtedly a requirement for an effective A/S sloop, a meeting took place in February 1932 to discuss design proposals. The Operations Division, the Planning Division, the constructors and the engineers were all represented, as were the Directors of the Signal and Tactical Divisions and Captain A/S. At this meeting, therefore, were high-level representatives of all the involved branches, and they produced a number of criteria which the future sloops should meet. It was agreed that these ships would need a speed of at least 19 knots to be able to chase surfaced Uboats, they would need to be good sea keepers in order to keep up with winter convoys in the Atlantic and they would need to have a building time of no more than seven months. It was stated that the current sloops were not able to keep up with convoys in poor weather, and that sea keeping and speed considerations made trawlers and ‘P’ type boats unsatisfactory for ocean convoy escort.This was accepted, but the point was made that in the early months of a war, before sufficient sloops had been built, the navy would have to rely on requisitioned trawlers.The Engineer-in-Chief appears to have done some very quick sums, and told the meeting that such a vessel, capable of 20 knots, would cost £250,000. The hull, he thought, would take four to five months to build and the machinery would take six to seven.11 The Director of Naval Construction (DNC) agreed to investigate the design of a 1,200-ton vessel capable of 20 knots, armed with a 4-inch gun, depth-charge throwers and asdic.Thus was sown the seed that became the patrol vessels of the Bittern, or Enchantress, class.12 A requirement for a less sophisticated coastal sloop was also agreed, and DNC promised to arrange for sketch designs of this type to be produced with the others. The sketch designs for the two types, produced only four months after the meeting, allowed for the particulars shown in Table 5. The Deputy Chief of the Naval Staff agreed with these figures, and proposed to include the construction of one trial ship of each class in the estimates for 1933 or 1934. By November 1932 it had been decided that 17 of the coastal sloops, and at least ten convoy sloops, were required ‘to form a nucleus of the anti-submarine organisation for the protection of trade’.13 It was conceded, however, that this programme would take some 15 years to complete. The Defence Requirements Committee, however, had not yet opened the tap of rearmament funding, and it was still not acceptable to the Treasury to have ships standing by ready for war. Once built, therefore, ships had to be found employment to justify their existence.This problem was summed 91 Copyright © 2003 George Franklin

BRITAIN’S ANTI-SUBMARINE CAPABILITY, 1919–1939 Table 5: Escort and Patrol Vessel Particulars

Source: PRO ADM 1/9350, Sketch Designs of Ocean and Coastal Sloops, June 1932.

up in a Plans Division minute towards the end of 1933: ‘The war requirements for convoy sloops will be very heavy. It is therefore considered that as many as can be employed in peacetime should be built.’14 Reversing the logic of this statement, the staff then went on to try to provide employment for as many escort and patrol craft as they could, be it as Admiral’s yachts, survey ships, on fishery protection, the Irish patrol or any one of a number of other tasks. The effects of this requirement were being felt as war approached, a later Director of the Plans Division writing that: Although it would clearly be desirable to start a vigorous offensive against enemy submarines on the outbreak of war, the extent to which we can do this is strictly limited by the number of A/S craft which we can afford to keep in commission in peace time.15 In the event, the first of each type of sloop appeared in the 1933 programme, and by 1936 six of each had been built, or were being built. It was planned to continue this programme at a rate of two of each type per year. The staff seem rather to have lost sight of the idea that these designs were to be held in abeyance until an emergency, and it was planned in 1936 to build three patrol vessels a year until 1942, and then reduce the rate to two per year.The sloops would continue to be built at the rate of two per year.16 In 1937 there was a semantic readjustment when the names of the various sloops, escorts and patrol vessels were changed. Patrol sloops of the Bridgwater class and convoy escorts of the Grimsby class were unified under the title of, simply, sloops, and the 510-ton coastal sloops of the Kingfisher class became patrol vessels. Old destroyers which had been 92 Copyright © 2003 George Franklin

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rearmed with HA/LA guns and fitted with asdic were now to be known as escort vessels, though, as discussed earlier, they still tended to be called destroyers.17 The convoy sloops of the Bittern/Enchantress-class also became escort ships. These changes were thought to be sufficiently important to justify the issue of two AFOs, 44/37 and 45/37, explaining the new designations. HMS Kingfisher appears to have been too light to be a good asdic platform, so subsequent ships were made heavier and thus more efficient. This did work, but it increased the unit cost to some £165,000, which was more than the Director of the Tactical Division thought reasonable for a vessel that would be mass-produced in time of war. One of the fundamental problems with these patrol and escort vessels was that, unlike the First World War Flower class, they were built to naval rather than merchant specifications, and so did not lend themselves to mass production. Notwithstanding this, the Director of Naval Construction circulated a paper in 1937 in which he proposed to consult two civilian shipbuilders about possible modifications to existing designs which might make them easier to mass-produce.18 The selected companies were Messrs Denny for the escorts, and Yarrows for the patrol vessels. The proposal was to develop the capacity to build an extra ten escorts and 30 patrol vessels, the first 20 per cent commissioning in the first six months of an emergency, a further 20 per cent every subsequent month. It was soon realised that the aim was not achievable due to the lead time required for production of certain key components, such as turbine blades, which would take nine months to manufacture. Nonetheless the paper continued to circulate, reaching the Director of Plans in early 1938, by which time the Naval Hypothesis for a war against Germany had changed, and it had become evident that the ten and 30 ships proposed would not be enough. It is not clear whether the proposals were forwarded to the builders, but this paper does at least tell us that it was becoming evident in the Admiralty that the existing classes would not allow for the rapid expansion required in an emergency. This dawning awareness led the First Sea Lord to ask, in January 1939, for the designers to investigate a design for a British equivalent of the American wooden 100-foot subchasers.19 The Director of the Tactical Division expressed doubts about the viability of this design, saying that the hull would be too big to use a type 130 motor boat asdic and too small for the type 127 sloop asdic to be effective.20 Nevertheless, he did his master’s bidding, and Commander P.F.Cooper, who had been one of the earliest A/ S specialists and was at the time working in the Tactical Division, was sent to Portland with a set of American designs to discuss the viability of the project. The plan appears to have died a death at this point, but was superseded by an altogether more successful scheme.



In January 1939 some of Captain A/S’s staff were visiting Smith’s Dock Company on the Tees to inspect an Admiralty trawler which was under construction when they happened across the details of a whalecatcher built by that company Enquiries indicated that these vessels could be built rapidly, as rapidly as could trawlers, and could be accepted exactly as they now are plus an asdic set, gun and depth charge equipment. The class has many advantages and may well fill the gap between the patrol vessel and the motor A/S boat.21 These 160-foot whale-catchers, known by the builders as the Southern Pride class, were driven at a maximum speed of 16 knots by their reciprocating engines, and would cost approximately £50,000 each. This clearly made them a lot cheaper than the other ocean-going patrol and escort vessels that were currently available or being built, but the Director of Naval Construction objected that, when whale-catchers had been considered in 1936, it had been decided that their subdivision was inadequate for a warship. He felt that they would founder too easily if damaged below the waterline, and the cost of further subdivision would be excessive. The low speed, however, was considered to be a far more serious drawback. The Director of Naval Construction, again objecting to them, pointed out that modern U-boats were thought to have a maximum speed of 18.5 knots, and the experience of the last war had shown that escorts needed a speed of at least 20 knots to be effective. In the face of these objections, he asked, somewhat brutally, whether ‘the 16 knot whale catcher [is] going to be useful’.22 The First Sea Lord, however, descended from his Olympian heights to decree that, While speed is certainly desirable, by insisting on high speed we put up costs and make it more difficult to produce in quantity. We must have numbers… If we can get a suitable design we could build some of these vessels in 1940. Also, we should be ready with a design in case of previous emergency. The Director of Naval Construction therefore informed Smith’s that at least one whale-catcher would be required. The builders proposed two designs, one oil burner of 190 feet and 1,170 tons which could steam for 3,000 nautical miles at its maximum speed of 16 knots or 4,000 nautical miles at 12 knots, and a 210-foot, 1,390-ton coal burner with the same performance figures. On 18 March 1939 the Director of Naval Construction wrote to a Mr Edwards of Smith’s Docks to tell him that a modified version of the oil burner, with a lesser top speed but greater range, had been approved by the Admiralty, but that no order could be placed until Treasury approval had been obtained.23 The first of these ships would cost £85,150 and could be 94 Copyright © 2003 George Franklin

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available in six months. Further ones could follow at a rate of one every three weeks, and if a greater production rate was required Smith’s were prepared, at a price, to make the drawings available to other builders. This first ship, HMS Gladiolus, was launched on 24 January 1940, and was followed by another 257 of a similar type built in Britain and Canada. The Flower class corvettes were not ideal; they were slow and cramped, they were poor sea keepers until the fo’c’sle was extended, and the low level of subdivision did indeed make them vulnerable to action damage.They were, however, in many ways the backbone of the Atlantic convoy system, and, even if war came earlier than expected, the ordering in peace of a prototype with a view to wartime mass production can only be described as a success. Roskill sums up their contribution to the war effort: ‘They crossed and recrossed the ocean escorting the slow convoys in all weathers and it is hard to see how Britain could have survived without them.’24

Table 6: Particulars of A/S Vessels Built 1919–39



It is interesting to note that when, in 1936, the Southern Pride design was being considered for Admiralty construction, the possibility of taking up the existing 50 members of the class in time of war, much as smaller trawlers were taken up, was also examined. The whale-catchers, however, worked in distant waters, and out of the whaling season they were laid up as far away as Cape Town, so could not be relied upon to be available in home waters in sufficient time to be useful.25 MOTOR BOATS In January 1938, Capt A/S and the Director of the Signal Division asked the British Power Boat Company to investigate the possibility of adding asdic equipment to a fast power boat.The asdic set, designed at Portland, was to be fitted to an existing hull, and the transducer, as mentioned in Chapter 3, was held away from the boat by a streamlined cantilever strut.26 The first of the anti-submarine motor boats, designated M A/S B 1, was built in 1938 by the British Power Boat Company and conducted initially successful trials at Portland. Commander Cooper, still serving in the Tactical Division, witnessed the boat in action and reported that ‘the asdic performance exceeded all my expectations’.27 He went on to write of the total absence of quenching, the effect experienced when a ship pitched so as to lift the transducer clear of the water, but did state that a trainable transducer would have increased the tactical versatility of the system. The boat had a wooden hull, was 70 feet long and had a range of 1,000 nautical miles at 20 knots. Its maximum speed was 30 knots, but it attacked at speeds between 15 and 20, still a good deal faster than a dived submarine could hope to travel. Its usefulness deteriorated significantly, however, in anything above a sea state four.28 As mentioned in Chapter 3, the type 130 asdic was fixed pointing in the ahead direction, and could only be directed by steering the boat itself. M A/S B 1’s first sister, the equally unexcitingly named M A/S B 2, had asdic which was directed on the beam rather than ahead. Although this could be operated without interference when as close as 100 yards abeam of another boat, it was not a tactical success and was soon replaced by an ahead pointing set. Attempts to fit a trainable asdic to the end of the streamlined strut were soon abandoned as impracticable.29 Although M A/S B 1 was initially successful on its own, it was envisaged that these boats would be used in groups, and the true effectiveness of such a class could not be determined until more boats had been built and group trials conducted. To this end M A/S Bs 2 to 6, which would all be of the same type as M A/S B 1, were ordered for construction in 1939.The Director of the Tactical Division described the M A/S Bs as being promising, but admitted that the idea presented ‘a new tactical problem in the use of asdics and involves limitations in endurance, navigational facilities and sea keeping generally’.30 He did, however, conclude his paper by saying that if the group 96 Copyright © 2003 George Franklin

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trials were successful the navy should procure a number of such vessels for coastal and local defence. Elsewhere it was suggested that they should operate in groups of six, the boats being commanded by Chief Petty Officers or Petty Officers, and the groups being commanded by commissioned officers. These groups would be held alongside at short notice rather than be used for patrols, as their strength lay in their speed of approach and attack rather than in an ability to keep the sea while on patrol.31 The general idea was that trawlers would be used for constant patrol of ports and anchorages, and if they found a submarine the M A/S Bs would sail and approach at speed to carry out the attack. It was even suggested by one enthusiast that a number of these motor boats could operate at some distance from their base if a mother ship was provided, as was the case at the time with submarines and their depot ships. Motor A/S boats were also proposed by Swan Hunter, who offered a Gordon Pratt-designed 110-foot steel hull, and Paxman and Ricardo, whose 100-foot steel boat would be driven at 25 knots by a diesel engine. With these proposals in mind, the Director of Naval Engineering asked at a conference in July 1938 whether it would be possible to fit asdic equipment to some other types of boat, to ensure that good results could be obtained from a variety of hull types and engine configurations.The conference agreed with this proposal, and the Controller agreed to arrange for the fitting of asdic to the existing MTB 102. In an unusual turn, and without setting his reasons on paper, the Controller announced four months later that ‘I have decided that MTB 102 is not to be fitted with asdic, and my previous decision of 3 October is reversed.’ A further four months on, however, his relief stated that ‘the trials of an asdic in MTB 102 is [sic] now to proceed with the least possible delay’. It is not known whether this conversion did take place, or how successful it was, but a further 18 M A/S Bs of the original design were certainly commissioned during 1940 and 1941. They appear, however, to have enjoyed little or no success in war, largely because the Uboats avoided the harbours and anchorages which they defended, and in the end the asdics were removed from the bulk of them, allowing the boats to be re-employed in the conventional MTB or MGB roles. An interesting suggestion with respect to fast A/S boats came from the Fairmile Engineering Company, who were not boat builders but specialised in the mass production of cars. Having studied the Admiralty’s requirement for an asdic-fitted power boat which could be mass produced in war, they proposed their own design for a 110-foot wooden hulled boat with a maximum speed of 22 knots and a range of 1,200 nautical miles at 12 knots.What distinguished the Fairmile proposal from the others was the production method. Rather than building the boats from the keel up in one yard, and possibly under licence at other yards, Fairmile suggested a mass production technique which would allow genuinely rapid construction of the boats. A large, not necessarily coastal, central 97 Copyright © 2003 George Franklin


production facility would manufacture the wooden hull components, which would be moved to a number of yards for assembly. Although some engines and gearboxes could be produced in Britain, rearmament was using up so much of British industrial capacity that Fairmile proposed that they should be imported from the United States, where the company had already identified suitable manufacturers. Further, Fairmile had identified six coastal yards which would be able to carry out the assembly and fittingout processes. These six yards had sufficient slips to build 31 boats simultaneously, meaning that over a 12-month period up to 124 boats could be produced.32 This scheme had the further advantage that it made use of small yards rather than the heavier shipbuilders that had been decimated in the building holidays following the Washington Treaty.33 Fully attuned, even in early 1939, to the need for peacetime economy, Fairmile suggested that having produced one boat for Admiralty trials they could switch production to foreign orders until an emergency demanded accelerated production. One Fairmile boat was ordered, the contract being placed in July 1939, and designated Motor Launch (ML) 1, later changed to ML 100. A large number were built during the war, and, while only a few were used for A/S work, they proved their value in a number of other roles. TRAWLERS The trawlers to be used in war would come from two basic sources, those taken up from commercial service and those specifically built by the Admiralty for the purpose. Basset, built in 1935 and employed until the war for training and trials at Portland, was the first A/S trawler to be designed as a prototype for rapid construction in war. At 461 tons it was heavy for a trawler and, in addition to A/S armament, it sported a single 4-inch gun. It was later joined by Mastiff, slightly larger at 520 tons, but in A/S terms essentially the same.These Admiralty trawlers appear to have been a success as the wartime Tree, Dance, Shakespearean and Isles classes were largely based on their design. The system for requisitioning non-Admiralty trawlers in time of emergency was established, or at least regularised, in 1933. Under the arrangements then laid down, Ministry of Agriculture and Fisheries officials, who regularly inspected fishing boats in the course of their other duties, would report to their local Admiralty mobilising officer on the suitability of vessels for war service. The mobilising officer, who was an Admiralty official, would then report to the Admiral Commanding Reserves, who kept a master list of trawlers and drifters that would be taken up in war.34 The mobilising officers, each of whom had an engineer and a shipwright to support him, were replaced by requisitioning officers in 1937. Trawler owners did not know whether their boats were on the list or 98 Copyright © 2003 George Franklin

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not, and it is doubtful whether the existence of the list was publicly acknowledged. By having an official of a civilian ministry make the inspections and recommendations on a discreet basis, rather than demonstrating the Admiralty’s interest in a boat, it was hoped that the possible eventuality of trawler owners demanding Admiralty retainers could be avoided. In 1937 it was pointed out that, following the replacement of the mobilising officers, with their engineers and shipwrights, by requisitioning officers, the Admiral Commanding Reserves had no technically qualified or experienced people on his staff, so was unable to verify the suitability of the ships which appeared on his list. A suggestion that this shortcoming could be overcome by the appointment of Admiralty officials to the Admiral Commanding Reserve’s staff for the purposes of making inspections was vetoed on exactly the grounds that this would reveal the Admiralty’s interest to owners.The problem was instead overcome by moving responsibility for earmarking from the Admiral Commanding Reserves to the Director of Naval Construction, whose technical staff was far better qualified to assess suitability. The Director of Sea Transport then took responsibility for requisitioning and conversion, but the Admiral Commanding Reserves retained his responsibility for manning. Sir Alec Black, of the Sir Alec Black Trawler Company in Grimsby, proposed a novel approach to the problem of trawler earmarking and requisitioning in 1936. Sir Alec was in the process of ordering replacements for a number of his trawlers, and he offered to have the new trawlers built faster and bigger than conventional trawlers, in order to make them more useful to the Admiralty during war. In exchange for this extra construction cost, from which he would gain little commercial benefit, he asked that the Admiralty pay an annual retainer of around £1,000 per trawler per year.35 The proposed boats would be around 190 feet long and have a maximum speed of 15 knots. The Directors of the Planning and Tactical Divisions, in a joint minute, supported the proposal. They argued that the navy clearly did not have enough escort vessels, that there would be a need in war to hit back hard and fast against a submarine offensive, and that £1,000 per year was negligible next to the £200,000 that a new escort cost.36 Vice-Admiral Henderson, however, as Controller, came out heavily against the scheme. He argued that it would take around a year for convoy to be properly established, so there would be no need for escorts in the early stages of the conflict, and that the Empire had sufficient shipping at its disposal, so could afford to lose shipping to submarine attack while a wartime programme of escorts were built. He also argued that a 13-knot trawler was entirely sufficient for the escort of a slow convoy, an odd argument given that later proposals to build 17-knot whalers met widespread opposition on the grounds that they were too slow for escort work.37 Henderson, it is widely agreed, was an extremely capable and dedicated man who brought many 99 Copyright © 2003 George Franklin


gifts to the post of Controller but his arguments in this case do seem to have been extraordinarily poorly founded.The Admiralty were, at this time, beginning to pay large armament suppliers to maintain a reserve of production capacity against future building plans. 38 This practice, enthusiastically pursued by Henderson, was contrary to Treasury policy, and the Admiralty was having to find some fairly under-the-table ways to pay the producers. It is possible that Henderson was unwilling to attract Treasury attention by paying a retainer to Sir Alec, when this might have compromised larger and more important projects. Certainly, the overt payment of capital retainers, even had it received Treasury approval, would have set an awkward precedent. In the event, however, the scheme was doomed to come to nothing, largely because, having been referred to civilian departments, it fell foul of the machinations of fishing industry politics. In 1938 there was another attempt to secure peacetime Admiralty funding for the fishing industry. Owing to overcapacity in the fleet, some 96 modern boats (or 25 per cent of the deep sea fleet) had recently been laid up on a voluntar y basis to make the industr y economic. Representatives of the Fleetwood fishing community proposed to the Admiralty that their Lordships could secure some of these boats from sale abroad by effectively chartering them.They suggested two schemes, one of which would see the Admiralty chartering the boats for £2 per gross ton per year, while the other would involve paying the owners, at cost price, for the expense they incurred in keeping the boats in harbour.39 The scheme was rejected on the general grounds that it was not the job of the Admiralty to keep the fishing industry propped up in lean years. Specifically, the spectre of sale abroad was countered with an extraordinary argument. The Admiralty, this argument went, would have first call on fishing boats in time of war, and there would always be enough for their purposes. If the boats were sold abroad, therefore, the civilian ministries responsible for food supply and shipping would be the ones to suffer, so the onus was on them to ensure that the boats were retained in the UK fleet. Whatever the moral or logical merits of this argument, it seems to have served to buttress the Admiralty position, and peacetime retainers were never paid to civilian trawler owners. A unit made up entirely of trawlers, and designated 2 A/S, was formed at Portland in the early 1930s in order to provide platforms for personnel training and tactical trials. The ten trawlers of 2 A/S were skippered by reservists, and fell into two groups, one commanded by a Commander, the other by a Lieutenant-Commander, both of the regular service.There were also four unit commanders, two being Lieutenant-Commanders and two being Lieutenants, all of the RNVR. This was thought to represent the level of command that would be required in war for a formation of a similar size.40 This was, however, a short-lived unit, and was reabsorbed into 1 A/S 100 Copyright © 2003 George Franklin

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in 1936, although its integral structure appears to have remained intact, and certainly there were trawlers at Portland right up to and beyond the outbreak of war. The system of trawler procurement was put to the test both during the Abyssinian crisis, when ten were commissioned, and during the crisis period immediately before the outbreak of war. By August 1939, 35 anti-submarine trawlers had been taken up,41 and on 29 August 1939 it was reported that ‘three A/S trawlers are now at Plymouth, five more will join when available and a further five in stage III’.42 The trawlers may not have produced dramatic results during the war years, but their presence certainly acted as a deterrent to mining operations and attacks on harbours. They were commissioned, converted, equipped and manned in accordance with the pre-war plans, and the fact that yet another part of the national anti-submarine system was activated with the minimum of fuss must weaken the argument that the navy was caught unprepared in 1939. AIRCRAFT AND AIRCRAFT CARRIERS The whole issue of naval aviation, both sea and land based, was a vexed one throughout the period under study.43 In essence, the Air Ministry, personified in Trenchard, believed that the long-range bomber had become the ultimate weapon of war. No target, they held, was immune, and the only answer to a bomber offensive was a counter-offensive in which the enemy’s airfields, factories and support services would be destroyed. The exercise of this form of warfare called for a unified air force capable of launching massive strategic attacks. Small branches of the unified air force could carry out subsidiary functions, such as direct support for naval operations, but such operations were only sideshows. The way to sink a battleship was to bomb it, and the way to stop submarines was to bomb them in their bases. This belief was outlined in 1935 by Group Captain A.T.Harris, Deputy Director of Plans in the Air Staff, who went on to become the wartime Commander-in-Chief Bomber Command. He wrote of anti-submarine work that, Whereas the methods adopted in the past were primarily defensive in their nature, the existence of long range offensive aircraft will in future provide us with a means of attacking the enemy’s main submarine bases and building yards and so of dealing with the threat at its very source.44 The RAF anti-submarine offensive would thus be directed against U-boats in their bases rather than at sea, and the best weapon to achieve this end was a large contact-fused bomb which did not have to be dropped against a moving target, or with any particular accuracy. Further, any mission flown 101 Copyright © 2003 George Franklin


against an enemy naval base was likely to come up against considerable antiaircraft fire; the bombers would therefore be well advised to fly at medium or high altitude. Clearly, a high-level aircraft dropping contact-fused bombs with at best moderate accuracy against a static target, having no sighting capability against a moving one, stood very little chance of hitting a submarine on the surface, and none at all of hitting one dived. It must be conceded here that the Admiralty was not free from similar belief in ‘forward defence’. It was, for instance, written in the Naval War Manual of 1925 that ‘if the enemy attacks trade, an attack upon some interest which he will feel bound to defend may result in the withdrawal of his forces from trade attack’ and more specifically that ‘attacks upon the bases of forces attacking trade is [sic] an important method of reducing the activities of these forces’.45 With the development of the German air threat the RAF line if anything hardened into a belief that nothing should be allowed to compromise the ability to hit back against the German industrial heartland. The Chiefs of Staff, in terms rather gentler than Harris might have used, reported the attitudes of the opposing sides to the CID in 1936: The main point of divergence between the staffs is that the Naval Staff are anxious to see a greater concentration of effort by the Royal Air Force on the provision of specialised aircraft allocated specifically for trade defence purposes than is considered desirable by the Air Staff. The latter point out that the offensive must take precedence, and that if this is to be achieved the limitations in the strength of the Royal Air Force imposed by practical considerations preclude the provision of a defensive strength which would meet the Admiralty’s views.46 Chatfield, not an officer normally given to supporting Air Ministry arguments, appears on this occasion to have conceded the point, because the paper concluded that ‘We [the Chiefs of Staff] are in agreement that this new [air] and, to a large extent, unknown factor is the principal danger to be apprehended.’ Thus was it ensured that Coastal, established as an Area in September 1919 and redesignated a Command in 1936, would remain the Cinderella of the air force, and that Bomber Command would receive priority in funding and allocation of scant aircraft construction resources. The need to ensure the continued existence of the independent force may have led to some deliberately destructive politics in the attitude taken by the air force. It has been argued that the drive for the air force first to establish itself as an independent service, and eventually to replace the other services, inherently precluded involvement in any activity that would subordinate the air force to one of the older services.47 Involvement in maritime trade defence, therefore, was to be avoided at all costs as it eroded the very basis on which the air force justified its existence. This kind of 102 Copyright © 2003 George Franklin

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argument may now seem extraordinary, but in the heated atmosphere of the debate at the time it was far from unusual. Once again we find Harris, shortly after the Germans had started openly rebuilding their U-boat fleet, defending, with questionable logic, the indivisibility of air: In view of the fact that the submarine and surface borne threats to trade may not develop at all, that they are very unlikely to develop in any serious proportion early on in a campaign, that they are in any case unlikely to constitute a vital menace, and as we know that the air threat to this country will be both immediate and vital, requiring all our resources to cope with it.48 Predictably, the navy and army held slightly different views. They both acknowledged that the strategic bomber was a useful weapon, and in the case of the Admiralty accepted the principle of a separate air force. However, they regarded the air offensive as being only one of the variety of weapons available, and utterly denied the extremist air force view that the new service would, eventually, replace both the older ones. They both held that the air offensive would in future be no more than one of the weapons available to the national armoury. Their argument went on that direct support for still vital naval and military operations was best conducted by separate air arms that would belong to and be controlled by the two older services. This controversy simmered, and occasionally boiled, from the end of the Great War until the late 1930s. Any number of committees and enquiries were appointed by successive governments to investigate War Ministry and Admiralty attempts to recover control of their own air arms, and the overall consequence was undoubtedly the retarded development of Britain’s maritime aviation capability. The compromise arrangement that was current through the bulk of the period under study was settled under the Trenchard-Keyes agreement of 1924, which divided responsibility for naval air power between the Admiralty and the Air Ministry. Shore-based maritime aircraft belonged wholly to the Royal Air Force, they were manned by RAF personnel, procured, equipped and maintained by the RAF, and as part of Coastal Area they were fully integrated into the RAF’s chain of command. Carrier-borne aircraft were designed and produced under RAF direction to meet navy performance requirements. Up to 70 per cent of the pilots of carrier-borne aircraft would be Royal Navy or Royal Marine pilots attached to the RAF, and all observers would be navy personnel.When embarked, the aircraft would be under the operational control of the navy, and when landed they would be trained by the RAF to meet criteria laid down by the navy. Crucially, though, all the aircraft would belong to the air force, which would thus have the main say over numbers to be produced. Moving from the strategic down to the tactical level, there were further 103 Copyright © 2003 George Franklin


differences about the appropriate use of air power, most of which sprung from the core disagreement. One of these was an extension of the view within the navy that anti-submarine warfare conducted through protection of convoys and ports was intrinsically defensive in nature, and therefore contrary to the supposedly offensive traditions of the service.Air Vice-Marshal A.V.Vyvyan, Air Officer Commanding (AOC) Coastal Area, verbalised the air force extension of this argument when he said of anti-submarine work that to provide aircraft in quantity was wrong in principle as this is a purely defensive policy… The nature of warfare in the air is eminently Offensive and not Defensive. To carry out an effective Defensive Policy entails such a huge expenditure in personnel and material to achieve small results that it is unjustifiable. Any Heavier-than-Air power available is much better employed in carrying out effective operations against the enemy’s submarine bases.49 While it is, of course, expensive in aircraft to mount defensive patrols to deter aircraft attack, the same does not apply to anti-submarine work. As we will learn in Chapter 6, the effectiveness of a surface ship convoy escort could be massively increased by the presence of only one aircraft searching ahead for submarines. Working alongside this Royal Air Force reluctance to commit resources to maritime trade defence was the Admiralty preoccupation with battle fleet tactics and the defence of trade against surface raiders, rather than submarines. The origins of this policy are discussed at length in Chapter 1, and it is sufficient here to say that, in the matter of anti-submarine aircraft, the positions of both departments coincided to produce a cumulative spiral of neglect. We will now move on to study the actual procurement of A/S aircraft, which took place against the background of this running difficulty.We can take the opening shots, as far as trade defence was concerned, to have come in the wake of a 1925 Naval Staff paper. In this paper the Staff worked out that for a Far East war, 44 shore-based maritime patrol aircraft would be required between Aden and Singapore for trade defence, while 175 such aircraft would be needed for a European war.50 At this time the flying boat was very much in vogue in Air Ministry circles.The fact that flying boats landed on water and so did not need strong undercarriages meant that they could be built bigger and heavier than land planes. This in turn meant that they could carry large fuel and cargo loads, and for a maritime Empire they were the obvious solution to many transport and communications problems. In the eyes of the RAF they were also the solution to problems of maritime aviation. The flying boat, with its huge range, could patrol the wide oceans from established harbours or improvised bases, and might eventually, following Trenchard’s policy of substitution, replace cruisers altogether. They might also have been useful for antisubmarine work, their great range allowing them to stay with convoys for 104 Copyright © 2003 George Franklin

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extended periods, but they were so big and so expensive that they were never likely to be produced in sufficient numbers to be really useful. It is also to be doubted whether their conspicuous size and large turning circles would have made them useful in the marking or investigation of any submarines they found. This inherent ungainliness would also make them easy targets for enemy fighter aircraft, and even enemy surface ship gunners. Despite a number of highly successful cruises in home waters and throughout the Empire, some of which demonstrated an impressive ability to operate autonomously for long periods, the days of the flying boat as an instrument of imperial control were coming to a close by the early 1930s. Essentially, land-based aircraft that flew, more efficiently, from the rapidly expanding network of shore aerodromes replaced the large flying boats. This was a pity as Coastal Area had to a great degree nailed its colours to the mast of the large flying boats, and with their passing found itself entirely lacking in experience of long-range, land-based maritime air operations.51 Between 1921 and 1925, the American military air enthusiast General Billy Mitchell conducted a number of trials in an attempt to establish that battleships could be sunk by aircraft. The trials revealed that a battleship at anchor without any form of defence could indeed be sunk, but gave no indications of what might happen in wartime conditions. Unfortunately, and perhaps predictably, the RAF’s bombing enthusiasts seized upon the results of the Mitchell trials to champion their cause yet further. A number of British trials were organised, initially against the HMS Agamemnon and HMS Opportune, and later against the converted and radio-controlled battleship HMS Centurion. In the words of John Buckley: the elderly radio-controlled battleship spent the next decade ploughing a lonely furrow up and down the English Channel whilst large numbers of eager pilots and aircraft potted away at her, determined to prove that they could hit—and possibly even sink—the mightiest of battleships.52 The results of these trials further fuelled the fires of the Admiralty/Air Ministry feud, and much has been written about the ensuing controversies. For our purposes, however, the significance of these trials is in the overall conclusion reached. The Admiralty felt that the success of torpedo bombers had been overstated because of the unreality of the conditions. The Air Ministry had no such reservations about the results of the bomber trials, and went away even further convinced that the bomber was the weapon of the future.The emphasis of RAF development therefore remained the strategic bomber force, and Coastal Area, the natural torpedo strike force, suffered further neglect. By the end of the 1920s the front line strength of Coastal Area was limited to some prestigious but militarily useless flying boats and two squadrons of outdated torpedo bombers.These two squadrons were sent to Singapore in reaction to the growth of the Japanese menace, discussed in Chapter 1. 105 Copyright © 2003 George Franklin


Still, however, there was no maritime anti-submarine capability in the Far East, and that at home was provided by four squadrons of Southampton or Blackburn Iris flying boats. This situation was not to change until plans for large-scale expansion of the RAF began to be drawn up in 1933.The first proposal, known as scheme A, allowed for an extra two squadrons of torpedo bombers, and four of general reconnaissance land planes, the latter of which could have been useful for anti-submarine operations around the coast. Before this could be put into action, however, it was superseded by scheme C, which allowed Coastal Area a total of seven land-based reconnaissance squadrons. Although these aircraft would be cheap, lacking in anti-submarine weapons and of relatively short range, they were to become the first of Coastal Area’s effective anti-submarine aircraft.To put the development into perspective, however, an increase of seven squadrons, or 126 aircraft, must be seen against the increase of 40 squadrons, or 500 aircraft, which was granted to the bomber force. Sir Thomas Inskip, as Minister for the Co-ordination of Defence, signalled a slight change in priorities in 1936 when he specified that Britain should plan to survive a knockout blow by Germany, and then wage a long economic war. Under this policy the offensive bombing force became less critical, and the defence of trade routes took on a greater importance. The air expansion schemes of 1937 and 1938—by which time they had reached scheme K—saw substantial increases in the numbers of land-based Coastal Command aircraft, and even modest increases in the numbers of flying boats. Enthusiasm at the increases in numbers of aircraft allocated to Coastal Command through the 1930s must, however, be tempered by a close examination of the aircraft themselves, for which we will start with the land-based aircraft and move on to the flying boats. As discussed, Air Ministry policy throughout the 1920s and early 1930s stated that land planes, which were necessarily lighter than flying boats and could clearly not land on the surface of the sea even in an emergency, were not suitable for long-range maritime work.This was in spite of the fact that the Americans were developing the Boeing B-17 land-based maritime patrol aircraft, which was to prove both cheaper and more effective than British flying boats. The Hawker Horsley, which had been built as a specialised torpedo bomber and, arguably, procured only to keep Hawkers in business, was becoming obsolete by the end of the 1920s. By this time the Air Ministry doctrine of indivisibility of air power had become so firmly entrenched that even Coastal Command aircraft had to be built with a capability to conduct long-range high-altitude bombing.The replacement for the Horsley, therefore, was the Vickers Vildebeest, which was essentially a medium bomber with a maritime capability.The specification for the Vildebeest stated that it was ‘to be designed and constructed to fulfil the duties of a bombing landplane with a high ceiling. It is also to be suitable for a coast defence 106 Copyright © 2003 George Franklin

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torpedo carrying landplane.’53 The reader will quickly appreciate that such an aircraft would be utterly useless if required to attack a submarine, and with its engines and airframe being optimised for high-altitude work would be entirely unsuitable for anti-submarine patrol, which was necessarily a low-altitude operation. The first land-based aircraft to be useful for anti-submarine work was the Avro Anson, specified in 1934 and ordered in 1935. Unusually, this was a maritime general reconnaissance aircraft built with no consideration of a bombing role.The Anson’s low ammunition load, of 360 lb, was not a major consideration in anti-submarine work and, in the face of the total lack of effective weapons, was academic anyway. Its operational range of only 600 nautical miles, however, meant that it could not stay with a convoy or in the position of a suspected submarine for as long as the already available flying boats. The lead time in specifying and designing aircraft was so long that, in the same year as the Ansons were ordered, the Air Ministry was considering the procurement of a replacement aircraft, which would be built to fulfil the scheme C rearmament programme. The development of this replacement was to produce one of the saddest tales of inter-war procurement, with three potential British designs being intermittently pursued with varying degrees of enthusiasm.The procurement of the Bristol Beaufort torpedo bomber, the Blackburn Botha and the multipurpose Bristol Bolingbroke was such an utterly directionless mess that by March 1938 the Air Ministry was despatching a team to the USA to investigate the purchase of American designs that were already in production. On 21 June 1938, 200 of the ultimately successful American Lockheed Hudsons were ordered for Coastal Command, and the first were arriving in the UK eight months later. The Bolingbroke programme was cancelled, the Botha was delivered in June 1940, but managed only 308 sorties before being declared useless and being removed from front line duties, and the Beaufort, which was eventually considered a success, entered service in January 1940. The Anson was thus the only useful land-based A/S aircraft to be used by Coastal Command during the years running up to the war, although it was joined by the Hudson in early 1940. In short, the Air Ministry, having declared that land-based aircraft were more economical, more effective for anti-submarine operations and more mobile than carrier-borne aircraft, utterly failed to supply satisfactory machines. The Anson had insufficient range to patrol even the North Sea and no effective offensive capability, and the Vildebeest, designed in the early 1920s, was a biplane torpedo bomber neither intended nor suitable for anti-submarine work. Regrettably, the procurement of flying boats went little better. The Supermarine Southampton, introduced in 1925 and in service through the bulk of our period, served with distinction both in the imperial cruising role and in diverse exercises. The Blackburn Iris, with three engines to the Southampton’s two, and slightly larger, suffered from a long gestation period, 107 Copyright © 2003 George Franklin


but finally entered service in 1929. Other flying boats in service in the early 1930s were the Short Rangoon, a three-engined machine based on a commercial design, and the Saunders-Roe London. By the mid-1930s the Saunders-Roe London and the Supermarine Stranraer, which was a descendant of the Southampton, were in RAF service in the medium-range role. There remained, however, a requirement for a long-range aircraft, and it was for this specification that Shorts entered with their Sunderland, while Saunders-Roe offered their Lerwick design. The sorry process of vacillation, which, parallel to that described above for land planes, characterised the competition between these two boats, falls outside the scope of this book.54 Suffice it to say that by the outbreak of war neither was in service in useful numbers, and that in 1939 negotiations for the purchase of American Catalina flying boats were under way. At the outbreak of the war, therefore, the RAF’s contribution to the aerial defence of Britain’s all-important trade routes took the form of the outdated land planes described above, two types of ageing biplane flying boats, and a small number of ultimately successful Sunderlands. This, the bombing enthusiasts would argue, was entirely satisfactory as the U-boats were to be annihilated in their pens, and their industrial base flattened by massed bomber attacks. No great study of the war is needed to pass judgement on this prediction. The procurement of aircraft carriers, being wholly a naval responsibility, caused less controversy than the procurement of aircraft, but the Air Ministry managed, nevertheless, to have a say in the process. During the war a number of small carriers were built which could be used to escort particularly valuable or vulnerable convoys, or could be tasked with supporting destroyers to carry out offensive operations against enemy submarines. While the interwar procurement of the large carriers, which were intended to work with the main fleets rather than in trade protection, does not concern us, the failure to procure small escort carriers is of some interest. Although there was no question that any force would enjoy more solid anti-submarine protection if there was a carrier in the group, the major fleet carriers were too few and too valuable to be used on convoy escort work. It must be remembered that the loss in September 1939 of HMS Courageous, which at the time was engaged in anti-submarine operations, represented an effective 25 per cent diminution in the RN’s available carrier capability. Occasional references have been found to the desirability of having escort carriers, which could provide constant air cover, attached to convoys, but in the event none were built until after the outbreak of war. Hague writes of ‘treasury parsimony’ being behind the failure to develop an escort carrier,55 but Admiralty and Air Ministry documents tell another story. An October 1935 Admiralty paper argued for light carriers of 14,500 tons carrying 15 light aircraft, which could support striking forces or escort convoys.56 These aircraft would be relatively cheap, low-performance amphibians, which would still be entirely adequate for anti-submarine patrol 108 Copyright © 2003 George Franklin

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work. While it was conceded that shore-based aircraft might be able to cover the choke points in a war against Germany, the point was made that for a Far Eastern war the mobility provided by carriers would be invaluable. The supporting argument asserted that ‘the most effective use must therefore be made of our Asdic forces, and aircraft will be needed for sighting and directing the Asdic groups towards enemy submarines’, and went on to suggest that attack groups based around these carriers might so damage the enemy submarine capability as to obviate the need for convoy. While this may have been an optimistic hope, it did have some logic of its own, and, as war experience was to prove, the combination of light carriers and destroyers in a supporting group was a deadly weapon against the U-boat. The Air Ministry, once again in the personage of Group Captain Harris, countered with the line that ‘the Navy never regard aircraft as otherwise than an ancillary weapon mainly for reconnaissance and defensive work, and the idea that every aircraft allotted to such duties is a dead loss from the total offensive power available from our strained resources simply does not sink in at all’.57 The Deputy Chief of the Air Staff added that ‘The need for mobility is emphasised and the erroneous [author’s italics] conclusion is reached that carrier borne aircraft are more mobile than shore based ones.’ Harris went on to argue that shore-based aircraft were in fact more mobile than carrier-borne ones, and that ‘the Admiralty paper is a typical example of the senseless and greedy waste of national resources in purely defensive measures’.58 The invective continued at some length, and seems, if only by volume and intensity, to have overcome the Admiralty arguments. Clearly, this exchange does not tell the whole story of the failure to procure escort carriers, other factors being the Washington Treaty limitation on overall carrier tonnage and the belief that any German submarine campaign would be fought close to the UK, but it does give some background to the controversy that ran between the Admiralty and the Air Ministry, rather than between the Admiralty and the Treasury. Of course, the Admiralty could theoretically build carriers without Air Ministry approval, but this would have been seen as little less than bloody-minded, and, if the latter would not co-operate in the procurement of aircraft, the project would have been entirely pointless anyway. Finally, it is interesting to note that the first wartime attempts to get ship-launched aircraft to accompany convoys were aimed at chasing off shadowing aircraft and bombers rather than at direct anti-submarine operations. NOTES 1 2

Stephen Roskill, Naval Policy Between the Wars, 2 vols, Collins, London, 1968 and 1976, Vol. 1, p. 412. Cmd 2476 of 27 July 1925, cited in Roskill, Naval Policy, Vol. 1, p. 452.


BRITAIN’S ANTI-SUBMARINE CAPABILITY, 1919–1939 3

4 5

6 7 8 9 10 11 12

13 14 15 16 17 18 19

20 21 22 23 24 25 26 27 28 29

PRO ADM 116/3603, Appointment of Additional Officers to HMS Osprey, D of TD paper, Dec. 1931. The argument was that two flotillas were needed for the asdic screen, one for the intermediate screen, two more for the close screen, one for the battle cruisers, two spare, two for home waters and a further three for convoy escort. PRO ADM 116/3603, Appointment of Additional Officers to HMS Osprey, D of TD paper, Dec. 1931. For fuller descriptions, see, among other sources, All the World’s Fighting Ships, 1922 to 1946, Conway Maritime Press, London, 1980; Peter Elliot, Allied Escort Ships of World War II, Macdonald & James, London, 1977; and H.T.Lenton, British Fleet and Escort Destroyers, Macdonald, London, 1970. Confidential Admiralty Fleet Order 1861, dated 2 Sept. 1937, in PRO ADM 1/10550, A/A and A/S Escort Vessels—Nomenclature. Antony Preston, V & W Class Destroyers 1917–1945, Macdonald, London, 1971. Quoted in Andrew Gordon, British Seapower and Procurement Between the Wars: A Reappraisal of Rearmament, Naval Institute Press, Annapolis, MD, 1988, p. 275. PRO ADM 1/9340, Types of A/S Vessels, Minute by Backhouse dated 11 Feb. 1932. PRO ADM 1/11596, Sloops, Minesweepers and A/S Craft, Policy Regarding, 1936. PRO ADM 1/9340, Types of A/S Vessels, Minutes of meeting 2 Feb. 1932. The confusion over the name of this class arose from the ship HMS Bittern having been renamed HMS Enchantress, and another ship then being called HMS Bittern. The class continued to be referred to in official papers by either one of the two names. NMM CHT 3/1, Memorandum by the Sea Lords on the Condition of the Navy and its Reserves, probably Nov. 1932. PRO ADM 116/2607, Sloop Requirements, Memo dated 1 Nov. 1933. PRO ADM 1/12141, Anti-Submarine Striking Forces, D of P memo dated 22 March 1939. PRO ADM 1/11596, Sloops, Minesweepers and A/S Craft, Policy Regarding, 1936. Minute by Head of M, Sept. 1936. PRO ADM 1/10550, A/A and A/S Escort Vessels—Nomenclature, 1937. PRO ADM 1/9417, Special Designs of Escort Vessels, Minesweepers and Patrol Vessels for Rapid Construction, Initial paper by DNC dated 23 Oct. 1937. Theodore R.Treadwell, Splinter Fleet: The Wooden Subchasers of World War II, Naval Institute Press, Annapolis, MD, 2000, gives a good account of the procurement and operation of the American version. PRO ADM 1/10174, Design of Anti-Submarine Vessels, Minute from 1SL to D of TD, 2 Jan. 1939. PRO ADM 1/10174, Design of Anti-Submarine Vessels, Minute by D of TD, 23 Jan. 1939. Ibid., Minute by DNC, 7 Feb. 1939. Ibid., Letter from DNC to Smith’s Docks, 18 March 1939. Roskill, War at Sea, Vol. 1, p. 133. PRO ADM 116/4005, Lists of Trawlers to be Taken up for War. PRO ADM 1/13802, Anti-Submarine Device—Removal of Prohibition of Patent Publication, 1938. PRO ADM 116/4458, Development of MA/S Bs and MTBs. PRO ADM 186/536, Annual Report of HM Anti-Submarine Establishment, 1937. PRO ADM 186/547, Annual Report of HM Anti-Submarine Establishment, 1938.


PLATFORMS 30 31 32 33 34 35 36 37 38

39 40 41 42 43

44 45 46 47 48 49 50 51 52 53 54 55 56

57 58

PRO ADM 1/10174, Design of Anti-Submarine Vessels, D of TD paper, 5 Jan. 1939, ‘Requirements for an Anti-Sub marine Vessel’. PRO ADM 116/4458, Development of MA/S Bs and MTBs. PRO ADM 1/10174, Design of Anti-Submarine Vessels, Fairmile’s proposal dated 6 April 1939. Gordon, Rearmament. Chapter 8 gives a vivid description of the damage that was done to the heavy shipbuilding industry. PRO ADM 116/4005, Lists of Trawlers to be Taken up in War. PRO ADM 116/3367, Construction of Trawler Fleet Suitable for War Service, Minute by D of TD dated 4 June 1936. Ibid., D of P and D of TD minute dated 10 Sept, 1936. Ibid., Controller minute dated 8 Sept. 1936. The debate surrounding ownership of equipment which was produced and held ready to allow for massive rearmament in the event of an emergency is a constant theme throughout Gordon, Rearmament. PRO ADM 116/3367, Construction of Trawler Fleet Suitable for War Service, Letter from representatives of the Fleetwood fishing fleet, and subsequent Admiralty minutes. PRO ADM 186/519, Annual Report of HM Anti-Submarine Establishment, 1935. PRO ADM 1/10189, Implementation of War Book Measures, 1939. PRO ADM 1/10547, A/S and M/S Vessels at Plymouth, 1939. For detailed discussions of this issue see Roskill, Naval Policy, both volumes, and John Buckley, Constant Endeavour: The RAF and Trade Defence 1919–1945, Keele University Press, 1995. The Air Ministry arguments are laid out best in Andrew Boyle, Trenchard, Man of Vision, Collins, London, 1962. Memo dated 1 Nov. 1935 from Harris as DD of P, in PRO AIR 2/2729, Proposed Squadrons and Aircraft Required for Sea Communications and Trade Protection in Time of War. ADM 186/66, CB 973, Naval War Manual 1925, p. 35, paras 233, 234. CAB 4/25, CID 1276-B, Food Supply in Time of War, 11 Nov. 1936, p. 3. Buckley, Constant Endeavour, p. 18 Harris as DD of P, 26 Nov. 1935, in PRO AIR 2/2729, Proposed Squadrons and Aircraft Required for Sea Communications and Trade Protection in Time of War. Memo dated 11 Nov. 1919, in PRO ADM 116/1836. Roskill, Naval Policy, Vol. 1, p. 472. Buckley, Constant Endeavour, pp. 24–30. Ibid., p. 48. Specification issued 1 Jan. 1926, in PRO AIR 20/3, cited in Buckley, Constant Endeavour, p. 51. The failure of Coastal Command procurement in the mid- to late 1930s is well covered in Chapter 4 of Buckley, Constant Endeavour. Arnold Hague, The Allied Convoy System 1939–1945: Its Organisation, Defence and Operation, Chatham, London, 2000, p. 77. PRO AIR 2/2729, Proposed Squadrons and Aircraft Required for Sea Communications and Trade Protection in Time of War, 1935, contains Admiralty and Air Ministry papers on the subject. Ibid., Memo signed by Harris, 1 Nov. 1935. Ibid.


6

Tactics CONVOY EXERCISES As discussed in the Introduction, the consensus in the published literature is that the navy failed utterly to practise the defence of slow convoys against submarine attack.This has, moreover, been extended by some commentators into an accusation that convoy tactics as a whole were not exercised.The facts as they appear today throw a different light on Roskill’s original contention. He quotes two authorities, the first of whom, Admiral Sir Geoffrey Miles, wrote that ‘I do not remember an exercise with a slow convoy screened by destroyers against submarine attack.’ Admiral Miles was a navigation specialist, and as such served on the staffs of the Rear-Admirals (Destroyers) of the Atlantic and Mediterranean Fleets between 1920 and 1925. After that he was appointed to HM Ships Iron Duke, Barham and Hood, and the Plans Division before going on to command a minesweeping squadron. He did not, therefore, serve on destroyers at any time after 1925, nor was he directly involved with destroyer exercises, so it would have been surprising if, 15 years after the event, he had had any memory of specific exercises in the defence of slow convoys. Roskill’s second authority was Rear-Admiral J.H.F.Crombie, who is quoted as speaking of the ‘total lack of convoy exercises’. Crombie was a specialist communicator whose seagoing appointments between the armistice and 1934 were to HM Ships Birmingham, Resolution, Hood and Repulse. He was, from July 1934 to August 1935, CO of HMS Thruster in 1 A/S, and later commanded the destroyer HMS Boadicea. During nearly all his time in Thruster the ship was alongside at Portland or day-running for repetitive and not very demanding exercises, many of which were in support of A/S School training. The ship did, however, participate in a few Home Fleet exercises, one of which was TP1, discussed in the ‘Offensive Tactics’ section of this chapter.1 During this exercise Thruster escorted a number of ships in and out of Portland, and it was the intention of the exercise planners that the ships should simulate either individual merchant ships or convoys. Three months later Thruster, still under the


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command of Commander Crombie, took part in exercise AD4, during the course of which she spent most of one day escorting the Italia at 10.5 knots. While both these exercises involved the escort of single ships, it was the habit at the time, for reasons of economy, to use single ships to simulate convoys. Indeed, the Admiralty definition of convoy was ‘one or more merchant ships or auxiliaries sailing under the protection of one or more 2 warships,’ and under this definition both these exercises were convoy defence exercises. Certainly, there is no good reason why tactics developed around a single ship should not be extended to larger convoys. It is thus surprising to read of Admiral Crombie’s ‘total lack of convoy exercises’. In order to look for exercises which may, contrary to Roskill’s statement, have taken place, one must define ‘slow’. In the inter-war years there was no formal definition of a slow or a fast convoy, but Roskill was writing from a post-war perspective so it would seem reasonable to take the wartime definitions. When convoys started to become classified as fast or slow, for instance the HXF and HX series, the limiting speeds were 12–15 knots and 9–12 knots respectively.3 As these brackets also applied to other convoys, it would seem that we can safely define any convoy with a mean speed below 12 knots as being slow. Hague’s exhaustive analysis of convoy statistics, however, shows that actual speeds were appreciably slower than this. Average voyage speeds of HX (slow) convoys were around 9 knots, and SC convoys were even slower at around 7.5 knots. If one reckons, as Hague suggests, that a zigzagging convoy has an overall speed of advance one knot below its speed through the water, one can conclude that the actual speed through the water of a slow convoy was usually between 8.5 and 10 knots. To make a conservative verification of Roskill’s assertion, then, we will look for interwar exercises with convoy speeds of 9 knots or less. With a very few exceptions, the only surviving exercise records are those which were collected in the CB 1769 summaries. These covered only a selected few of the most significant, but still give us details of a number of exercises in the defence of slow convoys against submarine attack. Table 7 lists those which are relevant. Many of these exercises also included other units, but they were all to some degree exercises in the defence of convoys against submarine attack, and five were without question slow convoys. It is conceded that five exercises over the period of 13 years studied in this book are not a tremendous number, but these five come from only a small sample. The direct records outlined above are further supported by other more oblique references in the source material, such as in the 1929 CB 3002:‘Several convoy exercises were carried out… The exercises were chiefly designed to discover the best dispositions for a small escort of A/S vessels such as might be expected in war.’4 In any event this evidence undoubtedly undermines Roskill’s contention that no such exercises took place, and by extension the subsequent literature which follows Roskill’s line. 113 Copyright © 2003 George Franklin

BRITAIN’S ANTI-SUBMARINE CAPABILITY, 1919–1939 Table 7: Convoy Defence Exercises

TACTICAL DEVELOPMENT When a ship goes to sea on an anti-submarine mission, it can find itself being given one of two entirely distinct tasks. The first involves offensive operations, which will mean working in known or suspected submarine operating areas in an effort to find the submarines and to engage them, or at the very least to limit their freedom of action.The second kind of operation is more defensive, and involves providing direct support to some maritime asset that is reckoned to be a target for the enemy’s submariners.This target may be a warship, a troopship or a merchantman, and the tactics used to defend it will vary according to the value attached to it and the speed at which it is moving. These circumstances require different approaches, and the bulk of this chapter has been subdivided into sections that look independently at each of these possible sets of requirements. Under defensive dispositions we will look first at the general principles involved in all defensive A/S operations, and the specific problems posed by surfaced night attack and the defensive employment of aircraft.We will then examine warship and merchant convoy defence. As a preliminary, however, it is worthwhile to look briefly at the status quo in A/S thinking that existed in 1919, when wide experience had been gained of anti-submarine operations but asdic was not yet in service. The eyeball was the only sensor available to aircrew, and, while surface ships 114 Copyright © 2003 George Franklin

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relied heavily on visual sightings, some employed passive hydrophones which could be lowered into the water to listen for the radiated sound of a submarine. The most effective ship-launched weapon for use against a dived submarine was the depth charge. Some ships did tow explosive sweeps, or paravanes, in the hope that they would make contact with a submarine and detonate, but this method was largely abandoned soon after the armistice. Gunnery and ramming were employed against surfaced submarines. Aircraft would drop contact-fused bombs against surfaced or shallow dived submarines, but it has to be said that this method had enjoyed the absolute minimum of success during the war. Aircraft had been found to be extremely useful when employed to search areas of ocean, and, although lacking an effective means of attack, they could force submarines to dive, so making them expend valuable battery power, reducing their mobility and limiting the submariner’s range of visibility. Surface ships conducting offensive sweeps or area patrols had been found to be substantially ineffectual, and the submarine was defeated largely through the use of convoy. Even in convoy escort, surface ships could do little against dived submarines, which were largely invisible to them, but a submarine which revealed its position by surfacing, showing its periscope or accidentally broaching could expect a large number of admittedly unaimed depth charges to be dropped in its immediate area. Theoretical tactics had been developed which allowed ships undertaking escort duties to station themselves in those positions which would afford best protection against submarine attack. The concepts of danger areas and limiting lines of approach, which allowed the escort commander to predict the direction of attack, are discussed later in this chapter. GENERAL PRINCIPLES OF ANTI-SUBMARINE DEFENCE Before discussing even the principles involved in protective anti-submarine operations, we need to address some of the philosophical arguments about the defensive or offensive nature of an anti-submarine escort, and to define some of the central terms. Because of the nature of the German attacks on Britain’s sea lines of communication, the terms ‘trade defence’ and ‘anti-submarine warfare’ have become, to some commentators, interchangeable. This is a great error, as trade defence had to do with a good deal more than anti-submarine warfare. Rather, it was the business of getting merchant ships across the ocean without interference from submarines, aircraft or surface raiders. Debates about trade defence will thus include such issues as convoy or independent sailing, convoy routeing, strategic deception, cover by heavy surface forces, and strategic interdiction as championed by Bomber Command. Anti-submarine warfare, however, is merely the business of denying the submarine the opportunity 115 Copyright © 2003 George Franklin


to operate profitably As this book is concerned with anti-submarine warfare rather than trade defence, we will not be entering into extended debate about the merit or otherwise of convoy, or the processes which led to its introduction. The anti-submarine escort commander who is assigned to a given force or main body can have one of two main aims: the first is to ensure the safe and timely arrival of the main body; the other is to ensure the destruction of any submarines that come within striking distance. Although the ‘safe and timely’ task may involve some trade-off between speed of transit and force security, this compromise can usually be arrived at without excessive debate, and the escort commander will find himself with a clear mission. He is to prevent submarines from firing on the force that he is protecting.A submarine detected ahead of the force is to be engaged if possible, but above all is to be avoided. A submarine detected abeam or astern of the force such that it is unable to make an approach is to be left alone, as is a submarine that, during the course of an anti-submarine action, has been forced into a position from which it will be unable to make an approach to the main body. When the escort commander is satisfied that the submarine can, for these reasons, no longer attack, the escort is to disengage and return to its defensive disposition around the main body, in preparation for the approach of further submarines. The escort commander, however, who is tasked to engage and destroy submarines will hunt any detected submarine, irrespective of the submarine’s ability to attack the main body, and will continue to hunt the submarine until it is destroyed or definitively lost, irrespective of the fact that this may leave the main body without protection during the hunt. The value of the main body, the number of submarines available to the enemy and the expected duration of the conflict will all inform the choice of mission. This debate was summed up in 1923: The object of all anti-submarine operations is the destruction of enemy submarines.While under certain circumstances successful defence must be the primary consideration in general the most certain means of obtaining security from enemy submarines is by carrying out a vigorous offensive against them.5 From this comes the debate about the defensive or offensive nature of convoy. One of the common naval objections to convoy is that it is seen to be inherently defensive in nature, and as such is contrary to the supposedly offensive traditions of the service. This feeling derives from a misreading of history, but nevertheless has to be overcome by advocates of convoy. When writing the Naval Staff History of the war against the U-boats,6 Barley and Waters sought to overcome the anti-defensive school by arguing that convoy, by forcing the attackers to come to the defenders, becomes an offensive operation. Although slightly academic, this definition of convoy as 116 Copyright © 2003 George Franklin

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an offensive disposition has gained wide currency among historians and tacticians, and for this reason the description in this chapter of convoy escort as a ‘defensive’ disposition may ruffle some feathers. The point needs to be made, therefore, that the term defensive has been used merely to achieve a convenient differentiation between different types of operations, and is in no way intended to challenge the philosophical assertion of convoy’s offensive nature. Escort dispositions, which are discussed at length during this chapter, do not change when the commander’s mission changes between protection of the main body and destruction of submarines. In either case, he will place his ships, if possible, in such a position that they will detect the submarine before it attacks. Where this is not possible, he will place his ships in such a position that they are able to counter-attack a submarine that has successfully fired against one of the main body units. The appointment of Paymaster Rear-Admiral G.H.W.Eldon Manisty in 1935 to the Naval Staff, with instructions to prepare the Trade Division and the Naval Control of Shipping (NCS) organisation for the wartime institution of convoy, represented the start of the steady development of a convoy system.7 Aside from building a staff at home, Manisty toured the world appointing reservists to act as NCS officers in the event of war, so populating all the world’s major harbours with men who understood, and were ready to institute, convoy. Certainly when the decision was made to adopt convoy in September 1939 the guides, publications, officials and structures were in place to allow the rapid and relatively painless institution of a complex and widely spread system. Credit must therefore go to the officers, many passed over for promotion, who staffed this Admiralty backwater. A number of documents and instructions written in this department survive, two of which are particularly worthy of mention. The first is CB 648, which carried the cumbersome but descriptive title of Mercantile Convoys: General Instructions for Port Convoy Officers, Ocean and Destroyer Escorts and Commodores of Convoy. This was produced soon after the armistice, and as such would seem to have been an attempt to round up the lessons learnt during the First World War.8 The second document, published in 1934 and clearly intended as an update of the earlier work, was entitled Mercantile Convoy Instructions.9 These documents had specific instructions for virtually all aspects of convoy, including suggested sailing formations, matters to discuss at pre-sailing conferences, and arrangements for command within the convoy .They also included predictions of how a submarine might choose to attack the convoy. These guides are important because their existence weakens another of Roskill’s lines of attack on the inter-war trade defence organisation, namely his allegation that ‘no coordinated instructions existed in the Royal Navy until the Western Approaches Convoy Instructions were issued under the stress of war in 1941’.10 117 Copyright © 2003 George Franklin


Lord Stanley, Parliamentary Secretary to the Admiralty, told parliament in March 1935 that ‘I can assure the house that the convoy system would not be introduced at once at the outbreak of war.’11 We have, however, already seen the extent to which material and manpower were being organised for convoy, and it seems to have been widely accepted, in the early 1930s, that an unrestricted submarine attack on trade would be countered by the introduction of convoy. It thus fell to the tacticians to work out how asdic would be used both in convoy defence and in the protection of large naval units. In the First World War, as has been discussed, the escorts were largely blind once the submarine had dived, and they had to rely on close screening to stand any chance of deterring submarine attack, while hydrophone-equipped vessels could patrol areas of known submarine activity. The advent of asdic extended the debate about the relative merits of screens and offensive hunting groups. In the early heady days of great faith in asdic, when the talk was of the ‘undetectable being detectable’ and a ‘transparent ocean’, there was a compelling logic behind sending groups of asdic-fitted ships to sweep the seas clean of submarines. When, however, it became evident that asdic was not all that had been hoped, the argument swung back in favour of the defensive asdic screen. The doctrine being issued by Portland in 1925 stated, quite categorically, that ‘the submarine should be left alone in the open sea, as the seas are too large to search for her’.12 By 1924, therefore, serious thought was being given to the issue of screen design. The principles of screen design, adhered to throughout the inter-war years and in many respects still current today, can be found laid out in a 1919 document.13 Figure 8 shows a diagrammatic representation of the problem faced by the escort commander. In order to achieve an attacking solution the submariner did not need to get inside the convoy, only within a reasonable firing range, usually reckoned to be around 4,000 yards. A perimeter of 4,000 yards was thus drawn around the convoy, offset forward to allow for the movement of the main body while the torpedo was running. This area, known as the torpedo danger zone (TDZ), had to be penetrated by a submarine intending to attack.The figure of 4,000 yards could be adjusted depending on visibility, sea state, changing estimates of torpedo range etc.14 The essential assumption in considering the submarine’s approach to the TDZ was that the speed of the target was greater than that of the submarine, so the submarine needed to start its approach from ahead of the target if the attack was to have any hope of success. It is important to remember that the maximum dived speed of a conventional submarine is a largely meaningless figure when considering the approach to, attack of and escape from a target.When attacking a defended target the submariner will be concerned to preserve as much of his battery capacity as possible to maximise his chances of escape. While a type VII U-boat, thus, may have 118 Copyright © 2003 George Franklin

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Figure 8: The Submarine Approach Problem (Source: PRO ADM 186/40)

been capable of 8 knots submerged, the CO would have been unwilling to use this very draining speed during his approach. Even the slowest of convoys, therefore, had some speed advantage over dived U-boats. In Figure 8 the lines marked as the limiting lines of approach are the lines ahead of which the submarine had to keep in order to be able to work into an attacking position. The faster the target, in relation to the assumed maximum speed of the submarine, the smaller the angle P, so the harder for the submarine to get into an attacking position. The water astern of the limiting lines was of no interest to the escort as a submarine here would not be able to catch the convoy up in order to attack. A submarine conducting a dived patrol in position A, making periodic periscope observations, would see the target approximately at A’, from where it would be able to work in to an attack position at A”, as shown. A dived 119 Copyright © 2003 George Franklin


submarine in position B, however, would not see the target through its periscope until B”, by which time it would be astern of the limiting lines, and so would not be able to attack. A surfaced submarine at B, however, would, with its increased visibility, be able to see the target at B’, and would then be able to manoeuvre for an attack. It is assumed, reasonably for daylight conditions, that the surfaced submarine would dive on sighting the target, and would thus make its approach at periscope depth and dived speed. A submarine which starts at C would only be in a position to attack if it happened to be steering, by chance, across the line of advance of the target and found itself at C’, which was within the surfaced danger area. If it first saw the main body at C” it would have lost the chance to make an approach. It can be seen from these three conditions that a submerged submarine needed to be within the dived danger area (DDA) to have a chance of attack, and a surfaced one within the surfaced danger area (SDA). These would thus be the areas which would need to be covered by the escort force if it were to be efficiently placed to detect or interfere with a threatening submarine. The shape of this diagram, and thus the front to be covered by the escort, varied with target speed, submarine dived speed, sea state, visibility and torpedo capabilities. If a submarine was detected ahead of a force and within the limiting lines, the heading of the force could easily and rapidly be altered to put the submarine outside the limiting lines, so making attack impossible.The escort commander could then make a decision about whether to detach escorts to prosecute the submarine, or to keep them in their stations to protect against further attackers.15 The idea of a zigzag as an anti-submarine tactic, albeit nakedly defensive, was well established during the First World War. The object was to disguise the main line of advance of a force of ships by constantly zigzagging together around that line. An attacking submariner, it was hoped, would see the force on one heading and would manoeuvre himself so as to be ahead of it for a torpedo attack. Some minutes later, when he again raised his periscope to check on the ships’ position, he would find that they had altered course and he was not ahead of them, as he had hoped to be. In an extreme case he might find himself outside the limiting lines of approach, so unable to attack, and in any event his approach would be made very much harder. The whole force would alter course together using preplanned zigzags executed either by signal or at a given time. Thus the ships’ logs of escorts often show entries such as ‘Commenced zigzag No. 23 at 1042.’ Looking up zigzag No. 23 in the relevant publication, the ship’s team would know to alter, for instance, 26 degrees to port at the 44th minute after the hour, then 14 degrees to starboard at the 53rd minute etc. If everyone followed the book, the whole force would, without any need for communications, alter course together, so confounding the submariner.


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A 1916 summary indicates clearly that the tactic was well established and gave some directions as to its employment: Alterations of course should not be so frequent that a submarine can estimate the possible course and speed and calculate when the alteration will take place; nor should they be so seldom that it is possible for the ship to have remained on the same course throughout the time she has been visible to the submarine.16 Although widely used during the First World War, the tactic of the zigzag was hardly employed at all in exercises up to 1932 for a combination of reasons, including submarine safety, fuel economy and a need to simplify the exercises in order to develop tactics. Asdic destroyers screening the Mediterranean Fleet during exercise RE in September 1932 did, however, employ zigzags,17 and this appears to have become the norm in the mid- to late-1930s. Another question concerned the spacing of units within the screen.18 Inter-war asdic sets could not search all around a ship in one transmission, but could only transmit along a cone of around 5 degrees. Thus, to search over an arc it was necessary to make one transmission, wait for the echoes to return (if there were any), move the transducer through 5 degrees, make another transmission etc. The length of time it was necessary to stay on each bearing depended on how long the furthest echoes were going to take to get back to the transducer, and that in turn was governed by the asdic officer’s estimate of the maximum effective range for the day. If oceanic conditions determined that a submarine was unlikely to be detected at a greater range than 3,000 yards, there was little point in waiting for echoes to return from 6,000 yards; the equipment would be more effectively used by moving it onto the next bearing as soon as the 3,000-yard echoes had returned. It took around half a second for the transducer to be moved through 5 degrees between transmissions, so for an asdic working range of 2,500 yards, which meant waiting 3 seconds for the echoes to return, the time between transmissions was 3.5 seconds. It was found that the best way to sweep was from 80 degrees abaft one beam through 5-degree steps to the ahead position, then from 80 degrees abaft the opposite beam again to the ahead position. This total involved 34 transmissions, as the ahead position was swept twice, and gave a basic sweep time of 119 seconds. Add to this a 25 per cent safety margin and the 8 seconds required to train from ahead to 80 degrees abaft the beam, and the total sweep time was 157 seconds. Figure 9 shows a submarine approaching a ship conducting just such a sweep, the sweep starting at time T, and being repeated every 157 seconds. Clearly, if the submarine is so fortunate as to be able to transit from A to B between T+(14) and T+(157) seconds, it will be able to avoid detection, passing the asdic ship with impunity. It is possible to derive a position for 121 Copyright © 2003 George Franklin


Figure 9: Asdic Sweep Pattern (Source: AL, CB 1870 (A)(39))

the point C, such that a submarine entering the asdic trace is unable to avoid being swept, as did the boat entering at A. From the position of C one can derive the effective angle, and effective width. The effective angle varied according to asdic range being used, ship speed and estimation of submarine speed. It was of course far from guaranteed that a submarine within the cone of the asdic transducer would be detected, but the chances of detection could be optimised by ensuring that the effective widths of adjacent ships abutted, or overlapped. For an ideal asdic screen, therefore, the spacing of the screening ships would be the same as or less than the effective sweep width in the prevailing conditions. To optimise the protection ahead of a force, therefore, it was necessary to determine the width of the dived danger area, and the effective widths for each of the escorting ships. From these one could calculate the number of vessels necessary to provide abutting effective widths within the dived danger area, and thus the number of escorts required for an effective sweep. The effective width could also be adjusted by using non-standard sweep patterns, for instance starting from 70 degrees rather than 80 degrees abaft the beam, or placing ships on a line of bearing rather than abreast, and having them sweep to one side only. Figure 10 (see p. 138) shows a screen in which both these methods were employed. 122 Copyright © 2003 George Franklin

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USE OF AIRCRAFT Aircraft tactics were applicable equally to the defensive screening of mercantile convoys and other faster, more valuable units, the speed of the aircraft being in either case so much greater than that of the ships that the tactics were interchangeable. For this reason this subject, rather than being subsumed into either the convoy or warship/troop ship sections, is afforded a separate section of its own. The 1926 CB 3002, or annual report on A/S progress, mentioned that fleet exercises had demonstrated the importance of ‘combined antisubmarine tactics by ASDIC destroyers and aircraft’, and noted that ‘this will receive more attention in the future’, but there is no direct indication that aircraft were getting involved in Portland exercises.They were, however, used extensively in the fleet exercises, where the first problems encountered revolved around communications. In the early days aircraft communicated with ships using flashing light, and the 1928 edition of the Battle Instructions specified that the outer air patrol should ‘pay attention to the outer limit [of their patrol area] as this is where submarines will first be located. They should close the extended screen at intervals though, to verify position and receive [visual signalling] signals.’19 The increased use of aircraft radios, which promised to solve many problems, actually introduced a number of new difficulties.The aircraft radio sets available in the 1920s were rudimentary and notoriously unreliable, with the result that aircraft, which were increasingly expected to operate beyond visual range from ships, often had great difficulty in alerting the ships to the presence of a submarine, or guiding them onto it.20 The limited radio fit in fleet destroyers also presented obstacles to the development of co-ordinated tactics. Ships in a screen were unable simultaneously to monitor traffic on aircraft and surface ship nets, and as it was necessary for the screen as a whole to be informed of traffic on both nets it became the practice for some ships to watch one net and some to watch the other. The method settled on in exercise AU21 was for the flotilla leader to watch the aircraft circuit, in order to obtain early warning of submarines. He would then use flashing light to communicate this information, and his instructions, to the rest of the screen. If he was within visual signalling range of the main body he could simultaneously send a contact report, which would provoke the commander of the main body to issue instructions for evasive action. If the screen commander was out of visual signalling range of the main body, as was often the case, it would fall to one of the screen destroyers to make the contact report to the main body. The time taken for an aircraft to contact the screen commander, the screen commander to make a visual signal to the screen, one of the screen to make a morse contact report to the main body, and the main body commander to issue his intentions was clearly too long for this arrangement to be satisfactory in a tactical environment.There 123 Copyright © 2003 George Franklin


was also a requirement for the main body commander to pass instructions to the aircraft, and for this purpose the 1934 amendment to the Battle Instructions specified that ‘vessels of the extended screen are responsible for passing to aircraft of the outer patrol all signals that affect them’.22 Awareness of the shortcomings of air/sea radio communications forced the introduction of other tactics. During exercise NX in 1928 it was found that aircraft could, by firing flares and diving over the position of a submarine, attract the attention of the escorts.23 A year later further methods had been developed, and the report on one 1929 exercise noted that aircraft had indicated detection of a submarine variously by circling the detected boat, firing flares, indicating ‘SSSS’ on flashing light, dropping smoke bombs or making radio contact. In one textbook action, an aircraft detected the presence of a submarine and was joined by HM Ships Rowena and Salmon, who both gained asdic contact and were later considered to have prosecuted the boat to destruction.24 The communications fits of destroyers improved with time: a 1928 paper on destroyer policy stated that all newly built ships were being constructed with one short-wave and one long-wave set, flotilla leaders being fitted with three sets.25 Aircraft radio fits were also starting to overcome technical problems, as shown in a report that noted that aircraft radios, which had until 1931 required constant tuning, were greatly improved, with the result that it was no longer necessary to carry three in an aircraft to keep one frequency open.26 The inherent difficulties in airborne communications were acknowledged in the Battle Instructions of 1928, which were amended in 1934 to an edition which remained in force until 1938. These instructions specified that the outer patrol, which worked out of visual range of the destroyer screen, was to be made up of multi-seat W/T-fitted aircraft, as the navigation and communications requirements were likely to swamp an unaccompanied pilot.27 The 1930 CB 3002 contained a note that aircraft had been used to some effect to counter shadowing submarines.This may have reflected the results of exercise OD in June 1929, in which an 8-knot convoy with a heavy escort and land-based air support was attacked by surface units and the first submarine flotilla. The defending aircraft met with considerable success, detecting and harassing surfaced submarines. One aircraft is reported to have found a submarine (L23) and ‘took three photographs of her on the surface at heights between 600 and 250ft. The aircraft approached down sun with engine throttled down. L23 does not appear to have observed the attack, and took no action.’28 How frustrating, then, for the aircrew to know that they possessed no effective anti-submarine weapons. Atlantic Fleet exercise AR, in November 1929, saw the Battle Fleet, its normal complement of destroyers augmented by 1 A/S, being attacked by no less than 15 submarines. In addition to the aircraft of HM Ships Furious and Argus, the flying boats of 201 Squadron RAF were supporting the fleet. 124 Copyright © 2003 George Franklin

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The destroyers were stationed ten miles ahead of the fleet, and the aircraft worked further ahead, there being no inner air patrol. Even though the fleet was not permitted to zigzag or undertake any evasive steering, only one of the 15 attacking submarines managed to make an undetected approach. Rear-Admiral (Destroyers) commented in his report that ‘Though only two submarines were sighted [from the air], the air patrols had the effect of often putting down the submarines when still well ahead of the anti-submarine vessels.’ As well as the implications for battery conservation, this would have meant that submarines in the surfaced danger area but outside the dived danger area would have been prevented from seeing and thus approaching the main force. Rear-Admiral (Submarines) confirmed this feeling when he wrote, in the same report, that the success of the antisubmarine force ‘encourages belief in the value of such vessels as a striking force well ahead of the Fleet, especially when air co-operation is available’. For policy development purposes, however, the final word lay in the Admiralty’s concluding comments that the submarines were badly handled and that ‘there is hardly enough evidence to show that this is the best way to use asdic vessels in home waters, where submarines are not easily detected by aircraft’.29 In mid-1930 the Atlantic Fleet exercised the defence of a 10-knot convoy, simulated by battle cruisers and battleships, against an attack by 16 submarines. The convoy was protected by two destroyer flotillas, aircraft from HMS Argus, and flying boats of the RAF. The destroyers in this case were split between a close screen and a distant screen six miles ahead of the main body. The tactics proposed for the submarines were practically identical to those later used by Dönitz for the wolf packs. Any submariner finding the force would shadow, making positional reports to his Commander-in-Chief, who would direct other submarines to intercept. Although one submarine did manage to shadow successfully, all attempted daytime attacks were detected and countered by the aircraft and destroyers, forcing the somewhat fatalistic comment from Rear-Admiral (Submarines) that ‘against enemy anti-submarine air patrol it is desirable when possible to maintain a dived patrol’.30 The same exercise conducted at night, it was conceded, would have presented much greater problems for the defending force. An investigation into the utility of flying boats was carried out by the Mediterranean Fleet in 1932. This seems to have taken the form of all Commanding Officers submitting their thoughts to the Commander-inChief, who drew conclusions and circulated the resulting paper to the Fleet and the Admiralty. Some Commanding Officers gave their own opinions and some commissioned wardrooms to conduct the study. Detailed reports do not survive, but various notes made on circulation are available.31 The Commander-in-Chief showed a sound understanding of the subject, acknowledging the usefulness of flying boat patrols in keeping submarines down and stating that ‘there is general agreement that, if aircraft accompany 125 Copyright © 2003 George Franklin


convoys, the danger from submarine attack will be reduced’, while qualifying his enthusiasm by conceding that ‘it is more than doubtful if flying boats, unaided, will ever be able to destroy or neutralise hostile forces (whatever their nature) employed in the attack on trade’.The Director of Plans, Captain John Cunningham, lived up to the model of an influential officer with no real understanding of anti-submarine in minuting under the Commanderin-Chief ’s comments that ‘it is not considered, however, that the use of flying boats for the protection of trade would materially reduce the numbers of auxiliary vessels required in war’ and, extraordinarily, going on to argue that ‘it seems doubtful whether the great number of aircraft required to search an area has been generally realised’. It is clear from these comments that Cunningham was still thinking in terms of clearing large ocean areas of submarines, rather than just sweeping ahead of a force.The Vice-Admiral Commanding the First Battle Squadron broadly agreed with Cunningham, but the Captain of HMS Resolution was openly optimistic, believing that ‘with a depth charge load equivalent to that of a “P” boat and a speed four times that of any surface craft, the flying boat would prove a definite menace to submarine operations’.32 While it is unclear if this study had any influence on policy, it allows an interesting insight into the spread of opinion about the subject. In particular, the failure of the Director of Plans to understand the subject backs up the point made in Chapter 2 that there was a narrow vertical column in the Staff who appreciated the problems, and that few of those outside that column were well informed. The limitations of aircraft when protecting a force in a narrow seaway were illustrated during Atlantic Fleet exercise AU in October 1930. The objective of this exercise was to screen battleships as they passed, in ones and twos, through a nine-mile-wide channel.33 The aircraft were successful in forcing the submarines to operate dived, making only intermittent use of periscopes. The narrowness of the channel, however, meant that the submariner could, even only occasionally using the periscope, be fairly sure of spotting the battleships as they passed. In other words, the battleships were forced, by navigational constraints, to put the submarines in the dived danger area, so negating the benefits of forcing them to dive. Defence was thus left to the asdic screen, which detected only 19 of the 36 attacks. Exercise RZ in the Mediterranean in 1933 saw the Battle Fleet successfully defended against submarine attack, and exercises in the Mediterranean in 1934 were again successful in that the aircraft were used to locate submarines and direct depth charge-fitted ships on to the target, even indicating the correct time to drop depth charges.34 The key point about the use of aircraft in screening operations was that, although they had little hope of inflicting damage on the submarine, they could summon escorts to attack it. In this way, their mere presence forced submarines to operate dived, so reducing the time the submarines could 126 Copyright © 2003 George Franklin

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spend recharging or conserving batteries. Similarly, aircraft could force dived submarines to lower their periscopes, so reducing their chances of sighting, intercepting and attacking surface units.The ability to see a dived submarine, in conditions such as prevailed in the Mediterranean, was thus not a prerequisite for the successful defensive employment of aircraft. Further, detection of a submarine ahead of the main body could allow the main body to alter course, putting the submarine outside the limiting lines of approach, so overcoming the danger presented without having to track or engage the submarine.35 One of the difficulties experienced in developing aircraft/escort cooperation concerned the time taken by destroyers, sloops and, especially, trawlers to reach the point being indicated by the aircraft. Clearly, an aircraft detection made in close proximity to the screen or hunting force presented few difficulties, but one made some distance off could be more problematic. A submarine which was forced to dive, for example, ten miles ahead of the screen might, as Captain D2 reported in 1932, ‘not offer sufficient chance of success to justify detachment of a hunting force’.36 If the hunting force were able to steam at 30 knots, it would in this instance take them 20 minutes to reach the last known position of the target, by which time a dived submarine could have moved by as much as two or three miles, making the probability of asdic detection very slim. The tactic decided on for such occasions was for the aircraft to conduct an expanding circle patrol around the last known position of the submarine, so keeping it down, and for the main body to alter course to put the submarine outside the dived danger area. The 1934 amendment to the Battle Instructions discussed the employment of an outer air patrol in conjunction with an extended screen. These instructions specified that when an aircraft made contact the nearest escort was to close the submarine, unless that involved being more than five miles out of station, in which case the chances of achieving a successful prosecution were not enough to justify detaching the ship. The contrast between air operations in the Mediterranean and the Atlantic was demonstrated by the difference between the reports on exercise NX, previously discussed, and TP1. In NX, aircraft working in support of asdic ships in the Mediterranean were able to guide ships onto submarines, while in the Atlantic exercise TP1 the submarines were lost once dived, leading the Commanding Officer of HMS Thruster to conclude that ‘the flying boats, in this exercise, proved of no assistance to the A/S vessels in searching for submarines’.37 Here again the subtlety emerges in the varying utility of aircraft. When escorting a main body, engaged in an essentially defensive operation, the requirement was to deny the submariner the opportunity to work into a firing position, so the aircraft only had to detect him on the surface and force him down to achieve success. In more offensive operations, where the surface ships were required to engage and destroy the submarine, merely forcing him down was not enough; the aircraft had to track the 127 Copyright © 2003 George Franklin


dived submarine for long enough for the surface ships to close and obtain asdic contact. It is worth mentioning a technique pioneered in the final months of the First World War and then, seemingly, abandoned, but which might have proved useful. These experiments involved the fitting of hydrophones to seaplanes, which could land on the surface of the sea, shut down their engines to minimise their own noise, and lower the hydrophone on the end of a ten-foot arm to listen for submarines. These hydrophones were directional and allowed a pair of aircraft working together to localise a dived submarine with some accuracy. Photographs remain of this equipment fitted to type F2 and F3 flying boats as well as a Short seaplane, but there is no evidence that the technique was pursued after the armistice.38 Attempts were also made to tow hydrophones behind airships, but the noise in the airship cabin meant that this method was found to be useless.39 Liaison between carrier aviators and the anti-submarine community appears to have been satisfactory, though the links between Coastal Command and the navy were less well developed. There was at least one attempt by the Admiralty to rectify this shortcoming; a letter from the Admiralty to the Air Ministry in 1936 requested that 217 Squadron, which often took part in Portland exercises, either move to a base closer to Portland or provide a liaison officer to the anti-submarine school.40 This liaison, which was felt by their Lordships to be ‘of considerable urgency’, was planned to allow investigation of anti-submarine co-operation, training of Coastal Command personnel in anti-submarine work and instruction of RN officers in the capabilities of anti-submarine aircraft. This sentiment was supported by Coastal Command, but when passed on to the Air Ministry, which was dominated by bombing enthusiasts, a sympathetic officer reported that ‘unfortunately I have come up against some very heavy artillery and as a consequence have had to retire somewhat hurt. I am very sorry that I have not been able to do any better than this.’41 In summary, during the First World War it was realised that aircraft could be useful in anti-submarine operations, and in 1926 aircraft/ship cooperation in submarine prosecution was formally identified as a subject that needed to be investigated. The early experiments took place in the fleets, rather than at Portland, and communications between the aircraft and the ships proved problematic. These difficulties were soon overcome, and in 1929 air patrols proved successful in countering shadowing submarines and, in theory at least, attacking those ahead of the force, to the extent that their use as part of an anti-submarine striking force was considered. Over time, limitations were identified, these involving the difficulties of providing effective cover at night or in narrow waters, and the fact that detected submarines were escaping because escorts were too slow to reach the position in which the aircraft had forced the submarine 128 Copyright © 2003 George Franklin

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to dive. By 1934, however, tactics had become largely standardised, with well-trained aircraft and ships able to work in combination to deter or prosecute submarines.The only serious shortcomings, apart from the night detection problem, concerned the paucity of suitably equipped and trained Coastal Command squadrons, and the lack of effective air-launched antisubmarine weapons. However widespread the agreement that aircraft were useful, vital even, for effective anti-submarine defence, there remained a number of questions surrounding the availability and provision of platforms. In 1931, the Commander-in-Chief of the Atlantic Fleet gave his personal view of the importance of aircraft in the anti-submarine role. In prioritising the roles of carrier aircraft he put reconnaissance, which he held to include antisubmarine work, ahead of gunnery, spotting or any attack role. In a discussion of the merits of carrier aircraft and those embarked in other types of ship he conceded that a force without an attached carrier was unlikely to be able to mount an airborne anti-submarine patrol. From this one can conclude that the majority of mid-Atlantic convoys would have to operate without air cover.42 The whole position was summarised in a 1938 Air Ministry paper on anti-submarine tactics and operations, which stated that a battle fleet would generally have enough aircraft attached to it to ensure anti-submarine protection. If trade was not in convoy, each of 14 designated coastal antisubmarine patrol areas would have an aircraft allocated by daylight hours, while, in the event of convoy being used, each convoy would have one aircraft for escort during daylight. If the movement of the main body was unrestricted and enemy submarines were working without surface or air co-operation, the air escort would work two hours’ steaming ahead of the convoy to interfere with surfaced approach. If the enemy was thought to have enough information to be able to make a dived approach, the aircraft would work in an inner patrol area just ahead of the convoy, thus having to cover less water and enjoying an increased chance of sighting periscopes or even dived submarines.43 SURFACED NIGHT ATTACK There is a common theme in the literature surrounding this subject which holds that the inter-war Admiralty failed utterly to appreciate the dangers posed by U-boats attacking on the surface under cover of darkness. Specifically, the accusation is frequently levelled that there was no awareness that a surfaced U-boat presented a poor asdic target. In this section it will be argued that the navy was unprepared to face surfaced night attack in spite of the fact that they understood the threat posed by boats which were difficult to see and made poor asdic targets. It will be suggested that nothing was done about this because, until the development of radar, there was simply nothing that 129 Copyright © 2003 George Franklin


could be done to detect the night-time approach of a well-handled boat on the surface. It seems that in the early days of asdic it was indeed not appreciated that surfaced submarines gave worse returns than dived ones. The report on a 1921 exercise involving two ‘P’ boats noted that ‘P40’s Asdic was working well, P38’s indifferently, and no echo could be obtained from the submarine, even when on the surface after the exercise’ (author’s italics).44 A year later, however, evidence was emerging that asdic was not fully effective against surfaced submarines, a report on one set of 1922 trials stating that ‘the submarine was first picked up at 1000 yards on the surface, and again at 1800 yards after diving to periscope depth, the echoes now being distinctly better’.45 By 1935 staff at the Admiralty Research Laboratory at Teddington were beginning to understand the refractive paths taken by underwater sound, and the deleterious effects of a negative velocity gradient were becoming apparent.46 A substantial section of that year’s CB 3002 was dedicated to the peripheral benefits which might be gained from asdic equipment. While the majority of this section is of minimal interest for the purposes of this study, one paragraph does stand out as being particularly revealing: ‘Whether surface craft can be detected, when their whereabouts are unknown, at ranges usefully in excess of low or night visibility will be matter for experiment.’47 Although specifically directed at destroyers and small torpedo boats, the results of such experiments would have given information about the usefulness, or otherwise, of asdic in detecting submarines making surfaced night approaches. Circumstantial and uncertain as this evidence is, it does provide another suggestion that there was an institutional and official awareness of the difficulty of using asdic to detect vessels on the surface. There is other more direct evidence that doubt existed about the effectiveness of asdic against surfaced submarines. During a 1935 exercise in harbour defence it was decided, for reasons of safety, that the submarines would attack on the surface. Little success was had against these surfaced targets, and It was suggested that submarines on the surface, and trimmed down, make bad Asdic targets, but it is more probable that the difficulty of detection is due rather to the submarines being able to see the patrols [which were using navigation lights], to keep continuously end on and to avoid close approach, and the difficulties of the patrol would not be so great in war.48 Someone in the Portland organisation clearly recognised the advantages the submariner had when making a night surfaced approach, but the collective solution in this instance appears to have leant on a simple act of faith and a good deal of optimism. There was, however, undoubtedly an official 130 Copyright © 2003 George Franklin

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awareness of the possibility that surfaced submarines might make bad asdic targets. In discussing static harbour defence asdic, the 1937 CB 3002 noted that a dived submarine could be detected at 5,000 yards, as against 4,000 yards for a surfaced one. More specifically, a 1937 Tactical Division paper discussing the use of surface ships as targets for A/S practice concluded that they were unsuitable as, ‘due to its shallow draught, a surface ship is an unreliable target’.49 A report written in April 1939 by the commander of the First Tribal Destroyer Flotilla gives further evidence that the efficacy of asdic against surfaced targets was causing concern. This report included a section specifically entitled ‘Detection of Surfaced Contacts’ in which it was reported that in two trials carried out against surfaced submarines detection ranges were found to average between 1,000 and 2,500 yards.50 Two comments elsewhere in the report are of interest: In a night exercise off Malta when Mohawk was being shadowed by submarines on the surface, they were detected by echo long before being sighted… While Cossack was anchored close to the harbour entrance at Alexandria during the 1938 crisis, Asdics were used successfully to give warning of the approach of Fast Motor Boats entering the fixed boom defences at night. These comments are significant, first, because they indicate that the general subject of detection of small surface contacts was receiving attention and, second, because in both cases detections were being achieved at tactically useful ranges. Faced with these, it becomes difficult to defend the widely expressed opinion that the navy ‘failed to appreciate that [asdic] was useless against a surfaced submarine’.51 The Naval Staff, it seems, were also aware that surfaced night attack presented a real problem. It was not uncommon for a submarine to be able to penetrate convoys or battle fleets by night.A fine example, far from unique, was L26 which, during the Mediterranean Fleet exercise OC in May 1929, passed right through the fleet, on the surface at night, ‘probably passing within a few hundred yards of [the destroyer] Valentine’.52 OC’s post-exercise report, which will have been a widely read document, made no attempt to shy away from the difficulties inherent in countering a submarine attacking or shadowing on the surface by night. The Captain of the first submarine flotilla wrote that ‘It is not only obvious, but has already been clearly established in many exercises, that submarines, with their low freeboards, should always be able to remain unseen at night.’53 The Rear-Admiral commanding the first battle squadron summed up: ‘This exercise has opened up a large field for investigation in regard to the tactical use of Asdic vessels in anti shadowing operations against submarines.’ It was the usual practice for submarines to shadow by night on the surface, 131 Copyright © 2003 George Franklin


so the foregoing comment must point, again, to an awareness of the vulnerability. The following year, during exercise AS, a surfaced submarine was able to spend the whole night tracking a cruiser from a range of a quarter of a nautical mile without being detected.54 In 1932, the utility of a surfaced submarine at night had not been forgotten, the Commander-in-Chief of the Mediterranean Fleet writing in his report on exercise QS that ‘a submarine after dark becomes virtually a slow and unhandy torpedo carrier which, due to her low silhouette, is unlikely to be spotted by enemy forces’.55 It is clear from this that there was a practical understanding of the problems posed by surfaced submarines. Still in question, however, is the extent of this crucial awareness within the wider navy. Significantly, the instructions for exercise AS in 1930 specified that submarines, for safety reasons, were to remain on the surface at night.There is evidence that this was a standard exercise instruction, which would indicate that night attacks by surfaced submarines would have been a familiar experience for the men of the fleets. The only surviving set of standard anti-submarine exercise instructions are those contained in CB 4000, dated 1938.56 These specified that, In peace, submarines are not allowed to dive during dark hours, except in purely submarine and anti-submarine exercises in accordance with the instructions in Chapter 7. They are, however, allowed to operate on the surface during dark hours but should, as far as possible, be kept clear of areas where surface forces are likely to make contact. The instructions referred to made it clear that diving a submarine at night was to be an exceptional practice rather than the norm.They specified, among other things, that the anti-submarine ships should have special lookouts posted, clear weather was required (not something to be relied on in the Portland area), the area should be relatively free from shipping (again, not a condition often found at Portland), the target ships should be on a steady course at a maximum speed of 20 knots and the submarine Commanding Officer was to be on the bridge for diving. These were not easy criteria to meet, so the vast majority of tactical night-time exercises carried out by submarines must have been conducted on the surface. Vice-Admiral Sir Ian McGeoch remembers exercising his submarine on the surface against ships in the Mediterranean during the inter-war period. Although he reports that navigation lights were generally used by submarines and ships alike, he does remember one exercise during which, as a Midshipman on the bridge of HMS Devonshire, he saw a darkened submarine operating on the surface.57 The rules laid out in CB 4000 certainly provided for submarines to operate


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darkened on the surface, but specified that they should only do so when the CO was on the bridge.58 The collective implications of this evidence are that fleet exercises would generally have been conducted with submarines on the surface, and, where necessary for training, the submarine would have been allowed to approach the surface ships at night, not always showing navigation lights. Further, the conditions required for night diving were far from guaranteed in the Portland area, so many of the Portland exercises conducted at night would have been against surfaced submarines. Certainly among the fleets, then, and probably among the Portland community, there was a substantial corporate experience of night operation against surfaced submarines. These findings are in direct conflict with Padfield’s unsubstantiated assertion that, during the inter-war period, ‘night surface attack was not practised’.59 In 1938 Admiral McGeoch, then a Sub-Lieutenant serving in submarines in the Mediterranean, submitted a paper for publication in the RUSI Journal on the subject of the offensive potential of the submarine. Among other points, Admiral McGeoch suggested that the Royal Navy could benefit from making more use of surfaced night attack. The RUSI submitted the paper to the Admiralty for approval and the Admiralty refused permission for publication. Padfield has made much of this refusal, claiming it as evidence that ‘another fatal flaw in the Admiralty’s Asdic-induced complacency was the assumption that enemy submarines would only deliver submerged attacks’.60 Closer analysis, however, points to a different conclusion. Some ten years after submitting his paper Admiral McGeoch was appointed to the Admiralty, where he was able to examine the docket concerning his paper. He found that permission had been refused on the recommendation of the Director of the Operations Division, who had described the subject as being ‘more suitable for a Staff College Lecture than a published paper’. From this it is difficult to impute that there was an objection to Admiral McGeoch’s ideas being promulgated within the service. The more likely conclusion, with which Admiral McGeoch now agrees, is that there were at least elements in the Admiralty which were aware of the surfaced submarine’s offensive potential, but that it was not desirable to have the implicit vulnerability of the Royal Navy’s surface ships highlighted by the publication of the paper in an open document such as the RUSI Journal.61 As an aside, the mere fact of the paper having been circulated within the staff for vetting approval will have gone some way to spreading the word about vulnerability to surfaced night attack, although the relevant section, on which Padfield bases his conclusion, comprises a mere seven lines in a 15-page paper.62 Much has been made of the blindness of the Admiralty, and specifically of the Naval Intelligence Division, in their failure to make a proper analysis of a book written by Dönitz, in 1939, on the subject of U-boat warfare.



The passage which has caused particular excitement is one in which he writes that The U-boat which is surfaced at night has the very great advantage over surface ships of a smaller silhouette. At night the hull of the Uboat is generally invisible, and if there is any sea there is no silhouette… Thus the night attack delivered on the surface provides the U-boat with a particularly effective method.63 There is no documentary evidence of the Naval Staff having made an analysis of this book, but such an analysis would hardly have changed the position with respect to surfaced attack; the navy, as has been demonstrated, was aware of the vulnerability and did not need to read books by foreign admirals to learn that surfaced submarines were hard to see. Some evidence does exist that the Air Ministry had given thought to the night-time conduct of U-boats. An Air Ministry memorandum written in April 1939 stated that ‘It is assumed that the tactics of enemy submarines will be similar to those employed in the War 1914–1918, in that they will operate at periscope depth during daylight and at dusk will surface to charge batteries.’64 This paper was circulated to and commented on by the Admiralty, but no note was made to contest this assertion. It is not a tremendous leap to conclude that an Admiralty which expected German submarines to patrol on the surface at night also expected them to attack on the surface at night. The clinching evidence, which points to an awareness of the problem within the Naval Staff and at the operational level, comes in the form of the 1934 Mercantile Convoy Instructions.65 So direct are the indications in this widely distributed document that it is worth quoting at some length: Para 185. With only her bow and a little of the upper deck above water, a submarine can steam from 10 to 11 knots. In this condition she is much less visible [than when fully surfaced] and can submerge to a safe depth within a minute. Para 187. If the night is starlight or not quite dark, a submarine can be fairly sure of seeing a ship before she herself is seen, and, under such conditions, she will probably operate on the surface with reduced buoyancy; in the moonlight, if her position is well chosen, she will be very hard to see. Para 188.The underlying principle of a submariners tactics on sighting a convoy is, if not interfered with, to use high speed in order to get ahead of the target either on the surface or submerged, and as a general rule, once in position the attack will be made with as little delay as possible. Para 189. If in a position to choose his form of attack there is a possibility of an experienced and skilful submarine Captain getting between two of the inner columns… 134 Copyright © 2003 George Franklin

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A submarine Captain will not get between the lines at night if he can avoid doing so, as he will be exposed to close range gunfire if sighted, but he will probably try for a shot from outside the escorting craft on the flank. The submarine could only have been exposed to gunfire if on the surface, so the last paragraph of this widely distributed 1934 document can only be referring to a surfaced night attack, the same surfaced night attack that David Henry tells us ‘was to come as a complete surprise to British anti-submarine forces’.66 To summarise, surfaced submarines made bad asdic targets, were hard to see in the dark and had been successfully used by the Germans during the First World War to make night attacks. Many currently claim that the interwar Admiralty was ignorant of asdic’s limitations against surfaced contacts, conducted no exercises against surfaced submarines at night, ignored the lessons of the 1914–18 war and was taken entirely by surprise when the Germans succeeded in repeating the tactic in 1940. The evidence here presented, on the contrary, indicates that the degraded performance of asdic against a surfaced target was understood, the fleets and the Portland organisation frequently exercised against surfaced submarines at night and they were only too aware that they were difficult to detect both visually and by asdic. The lack of available countermeasures in 1940 can then only be explained in one of two ways.The first is that the Royal Navy, aware both of a critical weakness and Germany’s history of exploitation of that weakness, was guilty of the most monumental, almost wilful, blindness and stupidity in failing to devise countermeasures. The second explanation, which seems more plausible to the author, is that the available technology did not allow for countermeasures; there was simply nothing that could be done to prevent a surfaced submarine making an approach and successful attack at night. Hydrophones would not detect a surfaced submarine against the background noise generated by merchant ships or heavy fleet units, the submarine could not be seen, nor could it be reliably detected by asdic. Even in the pressing conditions of war no other antidote than radar was developed to detect the approaching boat, though various methods were devised of illuminating the scene once the attack had been made. These, however, were risky tactics as they enabled the submariner to see his targets and pursuers better, and might alert other submarines in the area to the presence of the convoy. WARSHIP AND TROOPSHIP DEFENCE The Royal Navy has been the subject of further vilification for concentrating excessively on the defence of warships and fast troopships to the detriment 135 Copyright © 2003 George Franklin


of the more pedestrian aspects of trade defence. While it was undoubtedly the case that great, almost fatal, harm was done to the war effort by the Uboat attack on trade, it is worth speculating briefly on what might have happened had the Germans been successful in sinking a significant number of heavy warships. In the First World War the British Grand Fleet, without the benefit of asdic screens or the tactics discussed in this section, was left extremely vulnerable to submarine attack. This weakness so influenced Jellicoe’s thinking that he felt himself to be severely constrained in the North Sea, and it is arguable that it was this constraint which denied him the opportunity to engage the German High Seas Fleet on a number of occasions. It is unlikely, however, that freedom from such restriction would have had a significant effect on the overall conduct of the war; the Grand Fleet was, after all, despite the submarine menace, successful in denying the High Seas Fleet the freedom of the seas. At risk of straying into the counter-factual, it seems reasonable to suggest that, had the capital ships of Britain’s Home Fleet been more vulnerable to submarine attack in the early days of the Second World War, the great German raiders might have had a very much better time of it. At the very least, awareness of such a weakness would have denied the Home Fleet the ability to deploy on a purely offensive basis, as they did, for instance, in reaction to the sailing of the Bismarck in May 1941. In the worst case, successful U-boat operations against the Fleet might have caused the losses by attrition of which Tirpitz had dreamed, and, while it is inconceivable that the Germans would ever have been in a position to offer a Battle Fleet action, the operation of individual capital ships or raiding groups in the Atlantic would have been much less restricted. As shown in Chapter 1, much of the Royal Navy’s strategic planning in the 1920s and 1930s was aimed at a war in the Pacific against the Japanese. Such a war against a powerful surface fleet that would be virtually impossible to blockade, and a submarine force directed at attrition of enemy warships, would have been a very different matter from the Grand Fleet/High Seas Fleet conflict in the North Sea. Absolute freedom of manoeuvre would have been vital if the RN was to prevent the Japanese fleet from interfering with the very long lines of communication to and between Britain’s Far Eastern possessions. Had the British fleets failed to develop effective antisubmarine measures, such freedom of manoeuvre would have been denied, as it was to Jellicoe, possibly with disastrous consequences. The assertion that the Royal Navy concentrated on the defence of warships and fast troopships to the detriment of mercantile defence seems to be justified; what is questioned here is the assumption that the thinking behind that emphasis was flawed. While Roskill’s contention that the protection of slow merchant convoys was never practised has been shown to be untrue, the majority of the surviving records describe exercises using 136 Copyright © 2003 George Franklin

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escorts of a scale and strength undreamed of by Atlantic convoy commodores. These escorts would only have been provided for heavy fleet units, troop carriers or exceptional convoys such as those to relieve Malta. The conclusions often drawn, however, that such a policy was misguided and that grand strategy would have been better served by a withdrawal of the emphasis on warship defence, do seem open to debate. The fact that submarines had greater success against merchant ships than warships does not in itself mean that efforts made to defend the warships were wasted; rather it would indicate that the defensive tactics used were successful in at least discouraging submarine attacks. Further, the fact that the RN’s freedom of action prevented the German raiders from fulfilling their potential seems to support the assertion that sound anti-submarine tactics led, in part at least, to the failure of the German surface fleet. The assertion that German U-boats would, out of preference, have conducted operations against allied naval forces is backed up by the German Naval History of the U-boat: During the critical days before the annexation of Czechoslovakia in 1938 there were so few boats that they could not have had any appreciable effect on shipping. If war with England had resulted, they would have operated only against her naval forces.67 It was generally, and not unrealistically, assumed that a battle fleet at sea would have at least two flotillas of destroyers available to screen it.The spacing of ships within the screen was discussed in the ‘General Principles’ section of this chapter, but the actual placement of the screen, or screens, has yet to be covered. In general, the philosophy was to place the screen in such a position that any submarine lying within the dived or surfaced danger areas ahead of the fleet had a good chance of being detected. Clearly, surfaced submarines operating in the surfaced danger area could, by day, be detected by aircraft or non-asdic-fitted ships, which could force them to dive, so denying them an opportunity to press home an attack on the main body. The role of the asdic screen, therefore, would be to search ahead of the fleet in the dived danger area, where detection could only reliably be made by asdic.68 The question which had to be addressed thus revolved around the distance ahead of the fleet at which the screen or screens were to be placed. If the screen was too close, the submariner would be able to fire through it to hit his target without having to work his way through the screen. Place the screen too far ahead, though, and the submariner could dive deep while it passed over him, coming to periscope depth between the screen and the main body to reposition himself for attack. However, a screen placed some miles ahead might force the submariner down before he had sighted the main body, thus causing him to miss it altogether. The 1925 CB 3002, without making any recommendations, stated that 137 Copyright © 2003 George Franklin


the issue of distance between the escort and the main body was ‘a current tactical question’. In the 1929 edition the Commander-in-Chief of the Atlantic Fleet stated that a ‘close screen’ should be used in preference to the standard screen ‘whenever conditions for Asdic operating become unfavourable, or when a meeting with enemy surface craft is expected’. He also noted that, if there were surplus destroyers available when the main screen had been formed, those spare ships should be employed as a striking force rather than as a close screen. This striking force would be held in reserve behind the screen, ready to prosecute any contacts gained by the screen ships. An obvious benefit of the maintenance of such a striking force was that they need only have their asdic sets operating when there was known to be a submarine in the vicinity, so the asdic crews would be fresh and alert when most needed. By 1934, however, it was accepted that a close screen was, irrespective of conditions, a better use of assets, and the debate revolved around the position of that screen.That year’s CB 3002 stated that there should be sufficient sea room between the main body and the close screen for the screen escorts to be able to fall back to prosecute a submarine without getting mixed up with the main body. The report concluded that the position of the close screen depended largely on the prevailing asdic conditions, and that on a good day it could be efficiently stationed up to 4,000 yards ahead of the main body. In his report on exercise EC of June 1934, the Commander-inChief of the Home Fleet found that his close screen had been placed too close to the Battle Fleet, allowing HMS Achilles to be torpedoed from outside the screen.69 His conclusion was that the escorts should not be placed less than 1,500 yards from the main body units.70

Figure 10: Battle Fleet Asdic Screen for Exercise RZ, August 1933 (Source: PRO ADM 185/155)


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The close screen was again tested in August 1933, when the Mediterranean Fleet took part in exercise RZ.The Fleet was screened by a single destroyer flotilla in the formation shown in Figure 10. There were also two aircraft screens, one just ahead of the destroyers and one 15 miles ahead. A succession of submarines were positioned ahead of the fleet in order to attack, and all were spotted by the patrolling aircraft.With the exception of one submarine, these were ‘handed over’ to screening destroyers, which were considered to have carried out successful asdic and depth charge engagements. One submarine did penetrate the screen to attack the heavy units, having been detected but then lost by the aircraft screen. The exercise regulations did not allow the main body to zigzag or to make evasive alterations of course, and it was considered that when this submarine was originally detected the fleet could, in war, have altered course to put it outside the limiting lines of approach.71 The screen shown in Figure 10 is particularly interesting, as mentioned earlier, in that it shows the flanking ships sweeping only to one side, and all ships sweeping to 70 degrees abaft the beam rather than the more usual 80 degrees. By employing the tremendous number of escorts that would be available to the battle fleet, it was possible to establish two or even three screens ahead of the main body, so circumventing much of the debate about screen position. Certainly up to the mid-1930s the principle was that where two screens were available the outer, advanced or extended screen would be tasked to harass the submarines, keeping them down and so reducing their chance of seeing the main body in time to manoeuvre for an attack. The inner screen would form a ring of steel ahead and abeam of the main body, with the object of stopping the submarines approach to the main body.72 A novel tactic attempted during 1933 was to form the escorts into a ring around the main body, preferably in pairs, and then ‘expand’ the ring, prosecuting any submarines found and leaving the main body in the middle of a circle of sanitised water. By rapidly contracting the ring at dusk it was hoped that undetected alterations of the main body course could be achieved. This ‘ring’ tactic was tried in one exercise, and it was reported that all shadowing submarines were successfully detected, but there is no evidence of it ever having been tried again.73 Throughout this discussion it has been assumed that the screen around the main body was established to counter submarine attack only. Clearly, while commanders would sometimes be faced with only one threat, the enemy could reasonably be expected to concentrate all his available force in attack, so consideration would also have to be given to stationing for defence against surface and air attack. For a troop convoy or main fleet unit, this would not present a serious tactical difficulty as heavy fleet units would be available to counter surface and air threats, leaving the destroyer escort to concentrate on the anti-submarine effort. For a mercantile convoy with an exclusively destroyer or sloop escort, however, a requirement to counter 139 Copyright © 2003 George Franklin


an air threat would involve tactical compromises. Although there was a clear awareness in fleet exercises of the need to prepare for a multi-threat attack, the first indication that the Portland organisation was giving thought to convoy defence against combined air and submarine attack came as late as the 1936 CB 3002, which stated that ‘the whole question of trade protection has recently been under review for the purpose of correlating the methods of protecting it from attack from submarines and aircraft’. The measures taken in the early stages seem to have involved additions and alterations to ships’ weapon systems rather than tactical adjustments, so have little impact on our subject. These tardy rumblings of awareness at Portland contrast markedly with the attitudes in the fleets. A good number of the fleet exercises during the period under study, especially its earlier part, involved defence of the main body against combinations of surface, sub-surface and air attack. A typical example of such an exercise was NP, undertaken in the Mediterranean in January 1928. In this exercise six battleships, one battle cruiser, four cruisers, one destroyer flotilla and a number of RAF aircraft defended a convoy of 16 ships with a maximum speed of seven knots. The attacking force comprised five battleships, one battle cruiser, four cruisers, two destroyer flotillas, one aircraft carrier and four submarines.The screens for this exercise were designed for defence against surface rather than submarine attack, and all the attacking submarines managed to get themselves into firing positions against either the convoy or the heavy surface units. In the post-exercise report, however, the Commander-in-Chief stood by his identification of the enemy surface force as the major threat.74 This statement would seem to point to the Commander-in-Chief ’s strategic rather than tactical thinking. In 1927 the main naval threat to the Empire came from Japanese heavy warships, not submarines. The Commander-in-Chief Mediterranean, who could expect to find himself taking his fleet to the Far East in the event of a war with Japan, would thus be more concerned to defend himself against battleships and cruisers than submarines. Mindful of this, his dispositions in NP were not configured to provide for anti-submarine defence, and it was thus hardly surprising that the submariners found little difficulty in working themselves into firing positions. Eight years later, in exercise FC, a single submarine was able to make a good attack on a battle fleet steaming at 17 knots, and scored three hits on the Hood. Once again the screen was configured solely for surface ship attack.There were no destroyers or asdicfitted cruisers in the surfaced danger area, so the submariner’s success, while commended, was unsurprising.75 The reports on the vast majority of battle fleet anti-submarine exercises contrast markedly with those of exercises NP and FC. Typical examples were the Mediterranean Fleet exercises NO in 1927 and SF in 1934. In NO, the battle fleet was escorted by three flotillas of destroyers. Despite the submarines being placed directly in front of a fleet which was not permitted 140 Copyright © 2003 George Franklin

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to zigzag, only one of the six managed to penetrate the screen.76 In SF, the battle fleet was defended by three flotillas of destroyers, and attacked by four submarines. All the submarines were detected early, and it was, quite reasonably, concluded that ‘it is unlikely that in war they would have survived to fire their torpedoes at the battle fleet’.77 Another general tactical question revolved around the use of non-asdicfitted ships to augment an asdic screen, and was first raised in 1932. One answer to this problem underwent trials in exercise CB,78 when an extended screen of four pairs of asdic destroyers over a ten-mile front was placed ten miles ahead of the force, and the close screen was formed of non-asdicfitted destroyers. In the case of this exercise, ‘a submarine patrol line was encountered, and the fleet passed through the gap provided by the submarine that had been successfully attacked by one pair of destroyers’. This seems an odd tactic because the extended screen, covering a wide front and having large gaps between their effective widths, was lucky to detect a submarine, and the close screen might easily have been penetrated by a submarine operating at periscope depth.The better answer, thus, would seem to be to put the non-asdic-fitted ships in the distant screen, to keep the submarine down in the hope of it missing the main force altogether. Closer in, one could form a close screen of asdic-fitted destroyers with overlapping effective widths to prevent a dived or periscope depth approach to the main force. As the proportion of asdic-fitted destroyers increased, this problem diminished, and by the time war broke out virtually all of the RN’s destroyers were fitted with an asdic set of some sort. Exercise SK, in August 1934, practised the protection of a slow (9-knot) but valuable troop convoy, using three battleships, five cruisers and three flotillas of destroyers. The destroyers were ranged in screens four and eight miles ahead of the convoy to protect against submarines, as well as in columns down both flanks for air defence. The battleships were close on the beams and astern, and the cruisers further out on the flanks and astern. Not surprisingly, none of the attacking submarines got through to the convoy, only one managing to score a hit on a flanking cruiser. In summary, the issue which caused most debate in the area of battle fleet anti-submarine defence was the positioning of the screen ahead of the fleet. There was little doubt that the asdic screen should cover the dived danger area, but quite some debate about how far ahead of the main body it should be placed. By 1929 it had been established that a close screen was the optimum if asdic conditions were poor, and by 1934 the doctrine was to give the battle fleet a close screen whenever there was a submarine threat. In good asdic conditions this screen could be placed 4,000 yards ahead of the main body, and on a bad day as close as 1,500 yards. Any screen closer that 1,500 yards was deemed impractical as it would allow a shot to be take at the main body from outside the screen.This was still the accepted doctrine at the outbreak of war in 1939. 141 Copyright © 2003 George Franklin


The Portland establishment, tasked solely with anti-submarine matters, devoted very little energy to the problems of multiple-threat attacks, but these were addressed by the fleets in their exercises. The broad conclusion was that it was impossible simultaneously to provide for effective defence against submarines and other threats.The commander should thus establish the nature of the main threat to his force and configure his defence for that threat, accepting that his ships would then be vulnerable to other forms of attack. It was, however, generally believed that a close asdic screen would detect a high percentage of attacking submarines. CONVOY DEFENCE The intention to adopt convoy as the principal means of defending trade against unrestricted submarine attack was Admiralty, and probably government, policy at least from the early 1930s, as given by the CID in 1937: ‘To meet “unrestricted” warfare, we rely on the rapid adoption of the convoy system, and on being able to impress every available anti-submarine vessel into service as convoy escorts.’79 This position was also made clear to the public at large, and particularly to merchant ship owners, specifically through the medium of the Shipping Defence Advisory Committee: ‘The Chairman took this opportunity of assuring members at the second meeting of the committee that the convoy system is considered by the Admiralty to be the most effective form of protection against surface, submarine or air attack.’80 The Naval Staff did not enjoy absolute unanimity in support of this policy. For example, Admirals Pound and Fisher, as Assistant and Deputy Chiefs of the Naval Staff respectively, reasoned in 1928 that it would not be appropriate to introduce convoy in defence of mercantile trade.81 They were opposed, however, by, among others, the First Sea Lord, Admiral Sir Charles Madden, and in the end the Admiralty, the Board of Trade and the Ministry of Transport continued to plan for the introduction of convoy.82 In the event, therefore, of a submarine attack on trade which was conducted in accordance with the London Treaty, convoy would not be used, but if the enemy resorted to unrestricted submarine warfare convoy would be adopted. This was extended to cover RAF Coastal Command strategy. In the event of a restricted submarine attack, shore-based aircraft would patrol areas through which trade was passing, while an unrestricted attack would be met by attaching aircraft to individual convoys.83 It was assumed in the late 1930s that Germany would embark on unrestricted campaigns, and in fact naval control of shipping was taken as early as 26 August 1939, with the first formed convoy sailing on 2 September, the day before war was declared.84 It cannot be doubted, therefore, that at least from the re-emergence of the German submarine threat, and probably from the early 1930s, convoy was anticipated. 142 Copyright © 2003 George Franklin

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Whatever the consequences or the merits of the concentration on warship defence, the reasons for bias away from trade protection were disparate and many. There was a feeling in the inter-war Royal Navy that it was inconceivable that the UK would, in violation of the London Treaty, resort to unrestricted attack on enemy merchant ships. The doctrine for RN submariners was, therefore, almost exclusively aimed at attack of warships, preferably capital ships.85 In view of this, if an anti-submarine exercise was to be of any benefit to the submariners, it would involve them attacking the battle fleet. However aware the anti-submarine community might have been of the requirement to defend against foreign unrestricted attack on trade, participation in repeated battle fleet anti-submarine exercises will have concentrated minds on that area. Inevitably, the preoccupation of the ambitious seagoing officer is success in the next exercise, not the war that may or may not occur in five or ten years’ time. Provided with this motivation, surface ship officers could be forgiven for concentrating on the warship defence presented during exercises, rather than the subsidiary issue of trade defence. Once again, then, we see the development of a spiral of disregard. Under the strategic guidance of the Admiralty, who anticipated the institution of convoy, the anti-submarine establishment and the fleets did devote energy to trade defence, and as will be shown there was significant tactical progress over the period under study. A development which is first revealed in the 1928 CB 3002 is the suggestion that it was important to have at least one escort placed astern of the convoy in order to ‘retaliate on a submarine that has just attacked the convoy and also to keep a look out for submarines shadowing from the rear of the convoy’.86 This was a departure from the then current thinking, which put all assets ahead of the main body, and was the first of a number of developments that gradually moved the whole convoy escort to positions abaft the convoy’s beam before they once again, in 1935, moved to positions on either bow. This first change in doctrine may well have been fed by the results of exercise LA in January 1928. The escort dispositions for this exercise in defence of a slow (8-knot) convoy, which put the bulk of the asdic escort abeam or ahead of the convoy, allowed one submarine to work its way into the convoy during the night. She shadowed the convoy from a position on the surface slightly astern, before dropping out of sight at daybreak.87 It appears that she was tasked merely to shadow and report the convoy, rather than to attack. Such night shadowing would have been made very much harder had more of the destroyers been stationed astern of the convoy. The next development came in 1929 when, as a result of exercises in convoy defence with small numbers of escorts, it was decided that it was best to keep all the escorts on the quarters or astern of the convoy.88 The theory was that with a small number of escorts it was not possible to prevent a determined submarine commander from making an attack, but by placing 143 Copyright © 2003 George Franklin


Figure 11: Convoy Night Asdic Screen for A/S Defence Only: Exercise MA, 1929 (Source: PRO ADM 185/145)

the escort astern of the convoy one could optimise the chances of being able to make a counter-attack against the submarine.This may have provided little comfort to victims of the first, essentially unopposed, attack, but as the 1930 report said, somewhat hopefully, ‘if a good proportion of the ensuing hunts are successful, the object will ultimately be achieved by moral effect’. The tactic did, however, carry the cautionary comment that,‘when sufficient escort vessels are available, the positions ahead should be filled, but not to the exclusion of positions on the quarters and astern’.The disposition shown in Figure 11, designed to counter submarine attack by night, shows the theory of stationing escorts on or abaft a convoys beam. It seems to have been accepted in designing this screen that there was virtually no chance, by night, of detecting an attacking submarine until it had revealed its presence by firing torpedoes, usually from inside the screen. The four asdic-fitted destroyers on each flank would then be in an ideal position to turn in and hunt the attacker. The two destroyers astern of the convoy were clearly stationed to deter shadowers. The exercises carried out in 1931 led to the somewhat equivocal conclusion that ‘the escorting anti-submarine ships were disposed in positions ahead, beam and on the quarter or astern of the convoy. These positions would seem to be most advantageous for an A/S escort unit.’89 That report did, however, note the merits of positioning the fastest units ahead of the convoy, in order to deliver a rapid counter-attack. It is important to stress here that a counter-attack was not necessarily, as one might expect, an attack executed once the submarine had made an attack of its own. Rather, a counter-attack was any rapid attack made on a submarine that had been detected at close range or in circumstances where urgency prevented a steadily and deliberately developed attack. In a counter-attack, speed was of 144 Copyright © 2003 George Franklin

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the essence, in order to seize the initiative, and the accuracy of the depth charges could be compromised.Thus, detection of a submarine close ahead of a convoy would lead to a rapidly delivered anticipatory counter-attack to interfere with the submarine’s approach. In order to expedite such an attack, the fastest escorts would take the ahead sectors. It would also have been an advantage to put the fastest escorts ahead of the convoy so that they could sprint to attack any submarines detected by the air escort, which worked well ahead of the convoy. The 1932 CB 3002 gave a good summary of the broad position with respect to the state of anti-submarine defence of ships in the open ocean. While the men of the battle fleets could have taken comfort from the reassurance that they possessed ‘a high degree of anti-submarine protection by reason of high speed and the light craft and aircraft normally in company’, any merchantman would have found it stark reading. He would have discovered that ‘A/S protection will be afforded to mercantile convoys primarily by evasion’ and that ‘it is not envisaged that the escorting vessels will be able to prevent a submarine attacking the convoy’, but that reliance would be placed on the subsequent prosecution of the submarine. This attitude would harden in the following years, and in 1933 the policy was that the escort would attack the submarine once it had revealed its presence, and thus would ‘provide A/S protection to our convoys, not only by destroying enemy submarines but also by acting as a deterrent’. That this was Admiralty, rather than merely Portland, policy is indicated in a note written by the Director of the Tactical Division on a staff requirement for sloops: ‘Small numbers of the usual escort rule out any attempt at direct protection of the convoy, and make the detection of the submarine before firing largely a matter of chance.’90 The progressive consolidation of the Admiralty line is illustrated by the comments of a later Director of the Tactical Division in another staff requirement: To protect convoys against attack by submarines involves screening, for which the number of vessels required would be prohibitive. The anti-submarine requirement is therefore limited to the location and destruction of enemy submarines detected in the vicinity of the convoys.91 This opinion was duly reported to the Cabinet in a 1937 CID paper: Complete reliance can not be placed on detecting a well executed submarine attack prior to its delivery. On the other hand, once the attack has been delivered, the submarine’s chances of avoiding destruction by asdic-fitted escorts should not be too great.92 This was in agreement with the contemporary views of the RN’s submariners. Admiral McGeoch talks, from the submariner’s perspective, of the ‘childlike 145 Copyright © 2003 George Franklin


belief that we were not going to be detected’. He states that ‘we had a very good chance of getting in unseen and undetected’, but that ‘the chances of a submarine being destroyed once it had fired and revealed its position were high’.93 In order to provide for this attack of the detected submarine, it was felt that two asdic-fitted escorts would be required for a convoy of 20 merchantmen. If one considers that the exercise hunt success rate at this time was running at 54 per cent this does not seem such an unreasonable conclusion; few powers would persist in a submarine attack on trade if their boats had a 54 per cent chance of being destroyed every time they attacked a merchant ship. Notwithstanding this logic, there was clearly some doubt about the value of the two-sloop escort, and the 1935 CB 3002 promised investigations into ‘the extent to which an escort of only two ships may be expected to result in the destruction of attacking submarines, and the measure of protection given to convoys thereby’.94 The figure of two escorts compares with the 1924 projection of five escorts per convoy,95 a reduction which reflected the fact that, by the mid-1930s, most escort vessels were fitted with asdic.The exercise planners, particularly within the fleets, do however seem to have allowed themselves occasional flights of fancy: exercise ZP in 1938 saw a 20-ship merchant convoy being protected by no less than 14 destroyers! It should be noted here that when the Washington restrictions on construction applied, the RN was limited to 100 destroyers, which accorded roughly with the number that the Admiralty believed to be needed for trade defence.With the lifting of the Washington restrictions, the limitation on destroyer numbers became purely budgetary. The smaller, slower and lighter armed trade defence vessels were not limited by the terms of the Washington Treaty. We can summarise that the defence of mercantile convoys was afforded a good deal less effort than that of battle fleets or troop convoys, but work conducted over the period of this study did lead to substantial changes in tactics. In 1924 the practice was to station all the available escorts ahead of the main body, as one would for a battle fleet, but to accept that the screen would be thinner and less effective than one ahead of the battle fleet. In 1928 it was suggested that at least one escort should be kept astern of the convoy to deter shadowing submarines, and in 1929 the whole escort was moved astern of the convoy in a major change of philosophy. From this date it was implicitly accepted that it was impossible to keep submarines from attacking convoys, and the emphasis was placed on killing the submarine once it had revealed its presence by attacking. In 1931 this was refined by the suggestion that in some cases there might be enough escort vessels available to put some ahead of the convoy, preferably the fastest, in order to attack any submarine clumsy enough to reveal itself during its approach. In 1932 came overt acceptance that trade defence relied primarily on evasive 146 Copyright © 2003 George Franklin

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routeing, and that U-boats were not likely to be detected before putting in their first attack on a convoy. In 1935 there was a change of tactical doctrine, with the escorts being placed on either bow of the convoy where they would at least interfere with a submarine by forcing it to dive early in its approach. Realistically, however, they were still not expected to stop submarines attacking and, at the outbreak of war, convoy defence relied on the escorts reacting to a U-boat’s initial strike. The view that convoy escorts existed only to prosecute submarines which had disclosed themselves by attacking meant, in the extreme case, that there was no need to put any effort at all into convoy screening. In pursuance of this logic, it was decided in 1937 that only two escorts, the minimum needed for co-operative hunting and attacking, would be required for a 20-ship convoy. This clearly assumed that the enemy would attack with only one submarine at a time, and reservations about the value of a two-ship escort were voiced as early as 1935. The doctrine at the outbreak of the war was that, in order to protect the maximum number of convoys, a standard escort would consist only of two ships. OFFENSIVE TACTICS While the debate about how to form the screen was still ongoing, the increased use of aircraft to search ahead of the screen for submarines on the surface or at periscope depth once again offered up the possibility of forming offensive hunting groups. Extensive use had been made of patrols during the First World War, and they had generally proved ineffective. Although initial optimism about the performance of asdic led to a resurgence of belief in patrol, by 1925 the policy was fairly clear: ‘[Patrol] is defensive in conception and by itself it is uneconomical of fighting ships and unreliable as a protection against attack. It is therefore only effective when used in conjunction with other measures, such as convoy and cover.’96 This predicated the use of patrol on the availability of sufficient anti-submarine ships to provide both escorts and patrols, which was clearly optimistic. This view did persist for a while, and was expressed by Vice-Admiral Sir Osmond de B.Brock: ‘The main point of the Asdic system is that until something better is discovered, it does afford a satisfactory means of attacking submarines operating off a Port or in a focal Trade Area.’ 97 While Admiral Brock seemed, encouragingly, to understand the limitation of the equipment, especially for large-scale searching operations, he evidently still believed in the principle of patrol as an effective tactic. In 1930 the first properly analysed experiments were carried out with a ‘high-speed asdic sweep’, consisting of a number of vessels in line abreast, at 1,250 yards’ spacing, sweeping across an area at 18 knots.This might represent the conventional operating mode of escorts screening ahead of a battle fleet, 147 Copyright © 2003 George Franklin


or sweeping any area that was believed to contain a submarine. Although it was conceded that these exercises were ‘set pieces’, and so necessarily artificial, an impressive success rate of 77 per cent was claimed over 67 exercises, though the efficiency of a high-speed sweep degraded quickly in unfavourable weather conditions. If specific information was available about the position of a submarine, for instance if it had already been reported by an aircraft, it might be necessary for a striking force to sprint to that position before commencing its search. The submarine’s last known position was known as the datum, and the constantly expanding area of water in which it could be was described by what were known as furthest-on circles.98 In the case of the reported submarine the requirement was for a high sprint speed which took no account of the effectiveness of the asdic set at that speed, as the search would not start until the striking force was in the vicinity of the submarine’s reported position. In order to achieve this high sprint speed, asdic domes which could be withdrawn into the ship’s hull were designed for destroyers, allowing a maximum asdic speed of 20 knots and a maximum speed with the dome withdrawn of up to 32 knots. It was anticipated that this type of sprinting operation would most often be undertaken in coastal waters, especially in areas around harbours or convoy forming-up points. It was unfortunate, therefore, that the defence of these areas was eventually consigned to trawlers, sloops and other vessels considered inadequate for ocean escort work, many of which had maximum speeds lower than those of the submarines they were supposed to chase. The tactics for the approach to the datum were laid out in a 1938 Air Ministry document99 which refers to CB 3024, the ‘Manual of A/S Warfare’, no copies of which appear to survive.This specified that the largest possible number of ships should be engaged in the initial search, but once the submarine had been located only two should stay to conduct the hunt. If the searching ships were initially more than 10 nautical miles from the datum, they should approach in line abreast at 3,000-yard spacing; if closing from within 10 nautical miles, they should be at 1,500-yard spacing. The more precisely known position in the latter case allowed for the reduced front, and the closer spacing increased the chances (80 per cent for 1,500 yards against 40 per cent for 3,000 yards) of detecting a submarine which attempted to pass under the formation. These figures seem to result from generalised calculations based on the effective angle/effective width theory outlined in the ‘General Principles’ section of this chapter. A memorandum written by the Director of the Tactical Division in the same year gave some more instructions for hunting groups. He specified that they would only be efficient if they were able to put at least four ships to sea. Each group should thus consist of five ships, so that one could remain alongside for maintenance. He also felt that a group without an attached aircraft would be very limited, and that in order to provide continuous air 148 Copyright © 2003 George Franklin

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cover during daylight at least six aircraft would need to be allocated to each group.100 The memorandum, which was ‘intended to provoke study and probably argument as to the best means whereby aircraft and asdic vessels can cooperate in A/S operations’ divided offensive operations into three broad categories, depending on how much information was available about the submarine. During an ‘intelligence slight’ search of a large area where a submarine presence was suspected, the ships would proceed at around 16 knots at 1,500-yard spacings while the aircraft swept a 25-mile-wide lane. When carrying out an ‘intelligence medium’ search, normally in a restricted area such as the approach to a port, but still with no firm indication of submarine presence, the aircraft would work on an arc around 12 miles ahead of the surface ships. If a submarine had been reported to the group it would engage in an ‘intelligence considerable’ search. The aircraft would immediately go to search the area where the submarine had been detected, and the ships would steam towards it at best speed. When the surface ships reached the furthest-on circle, they would reduce to an effective asdic speed and would search the water within this constantly expanding area. In exercise NX in the Mediterranean in 1928, insufficient destroyers were available to provide a full asdic screen so consideration was given to their employment as an offensive striking force. The Commander-in-Chief ’s comments after the exercise noted: The exercise shows that the offensive qualities of even a small number of Asdic vessels may be of great value for the protection of the Fleet, provided that conditions are good for sighting submarines from the air. It is considered, however, that the standard Asdic screen should be employed under all conditions when numbers permit. This enables the offensive qualities of the Asdic to be fully employed, and at the same time a considerable degree of protection is afforded.101 In March 1935 an exercise, designated TP1, was undertaken to assess the utility of patrols and striking forces in a very local area. Portland was used to represent a fuelling point on an overseas trading route, there being seven independent arrivals and sailings every day. On the first day the two available anti-submarine vessels escorted the merchantmen in and out of the area, and on the second they adopted patrolling tactics, trying to sanitise the entire area. On both days the escorts were assisted by three flying boats of 204 Squadron RAF.102 It was thought that the lessons from this exercise would apply equally to the defence of single ships and convoys. The first day did not give encouraging results, with the majority of the merchantmen being ‘sunk’ by the submarines. Some asdic contacts were made, however, and three of the subsequent counter-attacks were 149 Copyright © 2003 George Franklin


considered to have sunk the submarine. Given, however, the accepted convoy defence doctrine that it was virtually impossible to prevent initial attack, reliance being laid on subsequent counter-attack, this inability to defend single ships is unsurprising. It is arguable, therefore, that had the ships arriving and leaving been in groups, or convoys, the percentage of sinkings would have been much lower, a maximum of one ship from each group having been a casualty. The second day, when patrolling tactics were used, proved disastrous for the anti-submarine forces. The submarines were able to operate virtually unhindered against merchant ships, and the anti-submarine vessels gained only one asdic contact all day. The Commanding Officer of HMS Thruster, one of the anti-submarine vessels involved, and Captain A/S respectively wrote in their reports: The patrol method is considered ineffective for a small A/S force… It is considered that a small A/S force is of no offensive value unless continually accompanied by a flying boat.103 It is not worth setting off at high speeds to search for a submarine at any but short distances.104 Notwithstanding these conclusions from the anti-submarine experts, the Admiralty summed up that, as well as providing for convoys and escorts, policy calls for offensive action to destroy the enemy as being an effective means of defence.To this end the intention is to provide striking force units at selected points around the coast…to carry out this intention it may be necessary for the patrol vessels to search a considerable amount of water.105 A special short exercise, XTF, was carried out in 1938 in order to test the effectiveness of striking force tactics.106 Two groups each of five destroyers were formed, one aircraft was airborne and one was on the ground at short notice, and five submarines were set to patrol in the area.The objective was for the surface/air force to detect and prosecute the submarines, so clearing the area prior to the arrival of a notional main body.The positions of the first two submarines were reported by the exercise directing staff, simulating a report from, say, a fisherman, and the surface ships set off to hunt their respective targets. Each one found its submarine, and in accordance with the doctrine two ships from each group were designated as the attacking units. In the following actions the two submarines were considered to have been destroyed. One of the other submarines, also reported by the directing staff, suffered the same fate, but the remaining two survived undetected. Although the surface ship tactics were found to be successful, poor air/sea communications meant that the aircraft were able to provide little or no assistance to the 150 Copyright © 2003 George Franklin

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destroyers.The crucial lesson of the exercise was that a patrol force was virtually useless unless given a good report of a submarine’s position. During the 1914–18 war much use was made of hydrophone-fitted trawlers, and between the wars a good deal of work went on, as has been shown, with a view to using asdic-fitted trawlers.The fundamental problem revolved around their being much slower and more susceptible to a heavy sea than destroyers and other naval vessels. This meant that the pitch, roll and yaw in anything more than a very moderate sea reduced asdic detection ranges dramatically, and the trawlers were so slow that hunts usually degenerated into tail chases, with the submarine often able to outrun its pursuer. As a result of these limitations it was early accepted that trawlers were suitable for harbour defence and limited coastal escort duties only, and should not be used for open ocean operations. The 1932 CB 3002 noted with evident exasperation that the results being achieved by trawlers were ‘inferior to the equivalent efficiency of asdic-fitted destroyers…this is unsatisfactory and tactics differing materially from those hitherto employed by trawlers will be tried out’.They were, however, considerably cheaper than warships, and in time of conflict could be bought, fitted with asdic, manned and readied for action in a very short time. Tactics employed by groups of trawlers engaged in search or escort duties were also limited by their maximum speed. In the event of one destroyer in a hunting formation obtaining an asdic contact, the procedure was for that ship to drop back to investigate. If the contact turned out to be a submarine, the other escorts would turn back to help, and if not, the destroyer could easily increase speed to catch up with the rest of the formation (screen speeds were usually around 12 knots, and destroyer maximum speeds were of the order of 30 knots). In the case of a trawler screen, or patrol, which might well be proceeding at a maximum speed of 10 knots, there was no possibility of a vessel which had fallen back catching up.The entire formation would thus have to stop and investigate each possible contact, much reducing the speed of sweep, and making direct escort duties impracticable. The rudimentary electrical equipment fitted to trawlers also caused tactical difficulties in that they were generally not fitted with radio equipment to communicate with aircraft, so were largely denied the tremendous advantages which were to be had from close aircraft support. Very few of the surviving documents give detailed descriptions of exercises involving trawlers and the development of their tactics, but there is no doubt that such exercises did take place, and some were directed at the protection of slow mercantile convoys. Indeed, a convoy protected by trawlers would, by definition, have to be slow. The 1936 CB 3002, for instance, tells us that ‘an exercise was carried out to investigate the employment of auxiliary A/S vessels [trawlers] for the protection of trade in coastal water’. Further, following the establishment in 1935 of the 151 Copyright © 2003 George Franklin


second anti-submarine flotilla (2 A/S), comprising ten asdic-fitted trawlers, we know that ‘satisfactory results [were] obtained with the equipment’, though no exercise records remain. In 1937 it was policy that each group of trawlers would be supplied with a Lieutenant or Lieutenant-Commander either RN, RNR or RNVR, who would be given specialist A/S training, but not to the same standard as the specialist A/S officers of the mainstream navy.107 By 1938, however, this requirement had increased to one Commander or Lieutenant-Commander and two Lieutenant-Commanders or Lieutenants per group of five trawlers. The reasons for this increase have not been found laid down in any document. It was, however, about this time that it became evident that in the early stages of war the trawlers would be required to perform escort as well as local defence duties (see Chapter 5). The very much more complex and responsible task of an escort group might have been thought to warrant the employment of the more senior command team. It is also possible that, as escort groups were more likely to be divided up than were local defence groups, the extra officers would be required to command the independently acting units. To sum up this section, the increasing availability of both shore-based and carrier-borne aircraft made the use of offensive patrols a more realistic option.Various exercises were devised, both to assess the value of offensive operations and to develop tactics, during which it was found that ships given a good positional report of a submarine had a good chance of successfully prosecuting it. The general conclusion of the anti-submarine community was that, in the event of an unrestricted submarine attack, antisubmarine forces would be more usefully employed in convoy escort than in offensive operations, and that patrolling ships were unlikely to be effective unless queued onto submarines. There remained, however, a misinformed body of opinion within the Naval Staff which believed that patrol, by dint of its inherently offensive character, would be effective in war. THE ENGAGEMENT Because ships necessarily lost asdic contact when executing depth charge attacks, it was the usual practice for them to attack in pairs. In this way one, which became the ‘directing’ ship, could hold contact while the ‘attacking’ ship actually delivered the charges. In good conditions the directing ship, which would aim to be on the beam of the attacking ship, could even signal the correct time to drop charges. It was unusual for more than two ships to execute an attack, as the extra ships added little, and their wakes and hulls could confuse the asdic picture.


TACTICS

The tactics discussed in this section all deal with a single ship attacking without the benefit of a second directing ship. This is because the policy was to develop the single-ship attack to the highest degree possible in order to provide for the worst-case condition.A ship that was proficient in attacking on its own, according to the theory, would have no problems taking part in a two-ship attack. So far the discussion has been about dispositions to be used to search for submarines or to prevent their access to a main body. We pass now to the actual direct attack by A/S ships on submarines. One of the main problems discovered during the early days of asdic was that there is a minimum range at which a submarine can be tracked by a vessel relying on an active sensor. In brief, each of the ‘pings’ sent out by the transducer lasts for a given length of time (in the early inter-war sets this was typically a quarter of a second). While the transducer is transmitting, it cannot receive any echo signal. If, therefore, an echo from a close-in contact arrives back at the transducer while the transducer is still transmitting, the received echo will be lost.The range at which contacts are lost in this way is referred to as the ‘dead range’, and can be showed to be one half of the pulse (or ‘ping’) length multiplied by the speed of sound in water. For an asdic set with a pulse length of 0.25 seconds, the dead range is thus 250 yards. Clearly, if a ship has to make the final 250 yards of its approach with no idea of what the submarine is doing, the problem of hitting it with depth charges which are necessarily launched over the stern of the attacking vessel becomes very difficult. In the early asdic sets the transmission was made by the operator using a morse key, and it was found that this led to variable transmission lengths and unpredictable dead ranges. This was overcome by incorporating circuitry which automatically governed transmission lengths and intervals.This could not eradicate the dead range altogether, but avoided some of the problems inherent in non-automatic operation. Automatic transmission equipment had, by 1928, enabled pulse lengths to be reduced to 0.05 seconds, below which it became difficult to obtain an echo. This length of pulse allowed a theoretical dead range of 50 yards.108 In practice longer pulses were used as they gave much more reliable echoes, and the practical dead range limit from pulse length was around 100 yards. There remained, however, another problem with close-range detection that had to do with the amplifiers in the receiving circuitry. In order to detect a contact at distant range it was necessary to use very sensitive receiving equipment and high-gain amplifiers, as the returning echo from a distant target was very weak indeed. Equipment set up, however, to process such faint signals was easily swamped by the relatively loud returns coming from close contacts, so it became impossible to process information about submarines which were nearer than approximately 250 to 400 yards from the transducer. Figures from 1927 indicated that the return from 6,000 yards



gave an echo strength of 0.014 millivolts, while one from 1,000 yards gave 80 millivolts, resulting in a range of input voltages well beyond the capability of any available receiving circuitry.109 This problem was initially overcome by the installation of a potentiometer which the operator could set to one of five positions according to the range at which he was operating. A later wartime development was introduction of automatic gain control which allowed distant and near contacts to be processed by the same circuitry. Another cause of dead range problems was the shape of the asdic beam, which was directional in the vertical as well as in the horizontal.This meant that although the beam subtended a fairly large angle, it was possible for a submarine to pass beneath it, especially as it closed the ship. In fact, although this resulted in a dead range, it was an advantage to the ship’s team, as it was reckoned that submarines went below the beam at a range of about six times their depth. Crude as it was, then, the range of the submarine when it was lost to asdic might allow a rough estimate of depth. Various tactics were introduced in an attempt to overcome dead range problems. The first was the Time Range Plot, or TR Plot. To execute this attack the escort commander would use the bearing and range information from the asdic equipment to alter the ship’s heading such that the submarine’s true bearing from the ship was steady; the ship and submarine were then on a ‘collision course’. As he then approached the submarine he would use a stopwatch to determine the rate at which he was closing the contact. When the submarine was within the blind range he would then use the stopwatch and his estimate of the closing speed to work out when he was ‘on top’ of the submarine, and would drop his charges accordingly. As he became more proficient he learnt to set his course to pass ahead of the submarine, and to drop his charges slightly ahead of the on-top time, so allowing the submarine to run on to the charges while they sank to their detonation depth. Even against a ‘dumb’ straight running submarine, such as those used during most Portland training exercises, this process required considerable mental agility and skill in shiphandling. An experienced submariner, free to make evasive manoeuvres, using hydrophones to assess the range, speed and heading of the attacking ship, could establish the time at which the ship was likely to become ‘blind’, and could then manoeuvre violently. As the TR Plot relied on the submarine having constant speed and course, such evasion clearly made the attack highly unlikely to be successful. It was in an effort to overcome the clear shortcomings of the TR Plot that the tactic of the ‘pounce’ was developed in 1925. The principle of the pounce attack was that the ship would approach the submarine very slowly, thus quietly, hopefully making it harder for the submariner to use his hydrophones. As the ship reached the dead range, at anything from 100 to 600 yards from the target, it would pounce, increasing to maximum speed and covering the distance to the submarine in as little time as possible. As 154 Copyright © 2003 George Franklin

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the ship was blind over the final approach the degradation in asdic performance consequent on the high pounce speed was not important, and the object was to be on top of the submariner before he had had time to react. The initial difficulty with the pounce lay in the fact that it is not easy to assess the distance covered by a ship which is rapidly changing speed.Thus, although the Captain might know when he started his pounce that the target was, say, 500 yards ahead of him, he had no reliable way to tell when he had covered that distance and was in a position to drop his weapons. For this reason the 1926 report states that the pounce, although promising, was proving no better than the TR Plot.With the development of the Chernikeef log (an impeller fitted to the hull which gave an accurate reading of the distance the ship had passed through the water, under development in 1926) it was hoped that the pounce would become more effective. By 1928 the pounce had indeed become the standard method of attack used at Portland and recommended to the fleets.The Chernikeef log was proving successful, and other innovations were reducing the dead range, so making the pounce more accurate. Although no figures are available for the success of exercise attacks in 1929, the texts of various reports indicate that the pounce was working well. Up to the late 1920s asdic operators determined a submarine’s position by timing the return of the echo with a stopwatch and noting the direction in which the transducer was pointing. With the pounce attack’s increasing requirement for accurate positional information came a need to automate the plotting of the submarine’s position. Among the benefits of such an automated plotter would be the ability of the ship’s crew to determine whether the submarine was moving. Although it is possible to sit a submarine on the seabed, it is very hard for it to keep depth off the seabed without making way through the water. If the ship could determine, using an automatic plotter, that the target was not moving through the water, it was hoped that it could be made easier to discriminate between submarines and non-submarine echoes from rocks, wrecks and other stationary objects. As the technique of the pounce was honed and the necessary equipment developed, so the submariners were exploring their own countermeasures. By 1928 some of the tactics still familiar today had been discovered. The first of these was to develop what would today be called an active intercept sonar; this enabled the submariner to listen to the asdic transmissions of the hunting ship. By listening to these transmissions he could establish the bearing of the attacking ship, and from the strength of the signal he could get a feel for its range.The second technique was to keep either the submarine’s bow or stern on to the hunting vessel, thus reducing the area off which the asdic pulse could be reflected. To confuse the hunter’s asdic even further, it was discovered that one could ‘proceed with bursts of high speed and large alterations of course’ to form a series of disturbances in the water which 155 Copyright © 2003 George Franklin


would reflect sound, so presenting the operator with a number of promising reflections, only one of which would be the submarine. Another tactic, and one which required a good deal of skill and luck, was to sit directly under another surface vessel. Any hunter would then see a reflection from that piece of water and assume it came from the surface vessel, rather than the submarine under it. Most crucially, though, submariners learnt to keep a constant speed and course until they heard an appreciable increase in the rate of turn of the hunting ships’ propellers. They knew that this represented the rapid phase of the pounce, when the ship was blind, so they could manoeuvre violently to avoid the imminent depth charge attack. Alternatively, if they could hear asdic pulses but no propeller noise, as the ship was steaming very slowly, they knew to manoeuvre violently when the propellers or engines became audible.This countermeasure was found to be so successful that a new tactic was developed, the Medium Range Constant Speed (MRCS) attack, first reported in 1930. The technique of the MRCS attack is best described in the words of the 1931 progress report: An attacking vessel lies about 900 yards from the submarine and estimates her movements. When these have been satisfactorily determined, the attacking vessel increases to maximum operating speed and closes the submarine on a steady bearing.This results in the target being closed for the last 700 yards of the run in at a speed of 18 knots. Any additional movements of the target during the run in can be corrected for during this short interval.The time of fire is estimated by a time range plot.110 The reader will immediately recognise similarities between the MRCS and the original TR Plot, which was abandoned in 1926. The intervening five years had, however, seen the introduction of new equipment which made the MRCS very much more successful than the original TR Plot. The first of these was the development in streamlining of domes which increased the speeds at which contacts could be held. While the ships running a TR Plot attack in 1925 were limited to 12 knots if they wished to keep contact, those running an MRCS attack in 1932 could easily make 18 knots, thus reducing the reaction time available to the submariner. The second change was the reduction in dead range, which made the final blind part of the approach run very much shorter. The third equipment advance was the automatic asdic plotter.This gave the officers of the ship a graphical representation of the positions of the ship and submarine, so making it much easier to determine the course to steer and the time to drop the depth charges, reducing the need for precise mental arithmetic in the heat of battle. The first automatic anti-submarine plotter was fitted to HMS Thruster in early 1929.This equipment took feeds 156 Copyright © 2003 George Franklin

TACTICS

from the ship’s compass and Chernikeef log to put a pencil mark on the plotting sheet once every minute. Information drawn from the asdic equipment guided another pencil to mark the submarine’s position, so showing the true course and speed of the submarine and allowing an accurate MRCS run to be made.When HMS Thruster steamed in a 7,500-yard circle, the pencil returned to within 25 yards of its starting point and submarine positions were found to be plotted with a maximum error of 0.5 degrees in bearing and 10 yards in range.111

Figure 12: Percentage of Success Rates in Asdic Hunting Exercises, 1925–38 (Source: CB 3002 Series)

The MRCS technique was practised with increasing success, and by 1934 improvements in detection ranges meant that ships were commencing their run-in from 1,200 yards, further decreasing the likelihood of the submariner detecting them before the attack. It is worth noting that when the MRCS attack was first introduced only A/S 1 and D4 were fitted with streamlined domes. The ships of D2 and D6 could not hold a contact at the required speed, so continued to rely on the pounce attack. No figures are available for the success of exercise attacks for 1931, but in hunting exercises those using the MRCS achieved a 60 per cent success rate, while those still relying on the pounce managed only 48 per cent. While not a clinching statistic, this would seem to indicate that the pounce had been rightly superseded. This was confirmed the following year when the MRCS ships achieved a 44 per cent success rate against the 30 per cent of those using the pounce. 157 Copyright © 2003 George Franklin


It must be borne in mind, when considering these statistics, that the methods of analysis still took no account of the relationship between depth charge depth setting and submarine depth, or of the movement of the submarine between depth charge launch and detonation. Figure 12 shows the fluctuating rate of success enjoyed by 1 A/S and the asdic-fitted destroyers in the fleets. It shows how the effectiveness of each tactic declined as submariners devised countermeasures, and how by the time war broke out 70 per cent success was being achieved. Moreover, these were hunts against submariners who understood asdic and had long experience of operating against it. NOTES 1 PRO ADM 53/99864, HMS Thruster log, March 1935. 2 Arnold Hague, The Allied Convoy System 1939–1945: Its Organisation, Defence and Operation, Chatham, London, 2000, p. 16. 3 Ibid., p. 109. 4 PRO ADM 186/476, CB 3002/29. 5 PRO ADM 186/500, CB 3002/32. 6 The Defeat of the Enemy Attack on Shipping, 1939–1945, originally CB 3304(1A), by the Navy Records Society, Aldershot, 1997. 7 Hague, Convoy, p. 20. 8 PRO ADM 186/40. 9 PRO ADM 239/126. 10 Stephen Roskill, Naval Policy Between the Wars, 2 vols, Collins, London, 1968 and 1976, Vol. 1, p. 537. 11 Parliamentary Debate, Commons, Vol. 199, cols 674–7, cited in Roskill, Naval Policy, Vol. 2, p. 228. 12 PRO ADM 186/447, CB 982, Progress in Torpedo, Mining, Anti-Submarine and Allied Subjects, 1925. This was the precursor to the CB 3002 series. 13 PRO ADM 186/40, CB 648(2), Mercantile Convoy Instructions, 1919. 14 AL, CB 4097 (1), Conduct of Anti U-boat Operations, and AL, CB 1870(A)(39), AntiSubmarine Manual, 1939, Part III. 15 AL, CB 1870(A)(39), Anti-Submarine Manual, 1939, Part III. 16 PRO ADM 1/8478/2, CB 0259, Remarks on Submarine Warfare, 1916. 17 PRO ADM 186/152, CB 1769/32(2). 18 The following is taken from AL, CB 1870(A)(39), Anti-Submarine Manual, 1939, Part III, but these principles are thought to have been current throughout the period under study. 19 PRO ADM 186/106, CB 01821. 20 See, for example, exercise NO in ADM 186/143, CB 1769/27(2). 21 PRO ADM 186/148, CB 1769/30(2). 22 PRO ADM 186/106, CB 01821. 23 PRO ADM 186/144, CB 1769/28(2). 24 Ibid. 25 PRO ADM 116/2685, Destroyer Policy, 1928.


TACTICS 26 27 28 29 30 31 32 33 34 35

36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

PRO ADM 116/2792, Shipborne Aircraft, 1931. PRO ADM 186/106, CB 01821, Battle Instructions, June 1928. PRO ADM 186/145, CB 1769/29(1). PRO ADM 186/146, CB 1769/29(2). PRO ADM 186/147, CB 1769/30(1). All the following are taken from PRO ADM 116/2862, Flying Boat Operations, 1932. It should be noted here that flying boats, until well into the war, did not carry depth charges. PRO ADM 186/148, CB 1769/30(2). PRO ADM 186/515, CB 3002/34 and PRO ADM 186/156, CB 1769/34(2). Conditions in the Mediterranean made submarines much more visible from the air than they were in Atlantic waters, to the extent that they could sometimes be seen even though dived to depths of up to 100 feet. The general view of RN submariners was that in Atlantic waters a dive to periscope depth was sufficient to escape from an aircraft, while in the Mediterranean it was ‘prudent to go deep when an aircraft was sighted’ (author conversation with Admiral McGeoch, 6 Sept. 2000). The Mediterranean Fleet, therefore, could be expected to be more enthusiastic than other commands about the employment of air assets in striking forces, although the author has come across scepticism about the claim that submarines could be seen at 100 feet. PRO ADM 186/151, CB 1769/32(1). PRO ADM 186/157, CB 1769/35. PRO ADM 186/406, CB 865, Hydrophones in Flying Boats and Float Seaplanes. PRO ADM 186/434, CB 01412, A/S Division Monthly Update of Experimental Work, Dec. 1918. PRO AIR 20/236, Anti-Submarine Work. Deputy Director Operations (Naval Co-operation) to Air Officer C in C Coastal Command, 28 March 1939, in PRO AIR 20/236, Anti-Submarine Work. PRO ADM 116/2792, Shipborne Aircraft, report by C in C Atlantic, 8 May 1931, ‘Review of the Situation Regarding Aircraft in the Fleet’. PRO AIR 15/38, Air Tactics, A/S Operations, 1938. PRO ADM 1/8609/138, Asdics: Anti-Submarine Flotilla—State and Proceedings, w/e 9 Jul 21. PRO ADM 186/758, HM Signal School Experimental Department Quarterly Report, March 1922. See Appendix A for an explanation of basic asdic theory. PRO ADM 186/522, CB 3002(35). Ibid. PRO ADM 1/12140, A/S Policy, Tactical Division memo, ‘Provision and Training of A/S Personnel’, 1937. PRO ADM 1/9942, Capt. First Tribal Flotilla, Report dated 18 April 1939, in C in C Med Half Yearly Report on A/S Operating, 26 May 1939. Roskill, Naval Policy, Vol. 2, p. 228. PRO ADM 186/145, CB 1769/29(1). Ibid. PRO ADM 186/147, CB 1769/30(1). PRO ADM 186/152, CB 1769/32(2). AL, CB 4000, Instructions for Submarine and Anti-Submarine Exercises, 1938.


BRITAIN’S ANTI-SUBMARINE CAPABILITY, 1919–1939 57 58 59 60 61 62 63 64 65 66 67 68

69 70 71 72 73 74 75 76 77 78 79 80 81 82

83 84 85 86 87 88 89

Author conversation with Admiral McGeoch, 6 Sept. 2000. AL, CB 4000, Instructions for Submarine and Anti-Submarine Exercises, 1938, p. 40. Peter Padfield, War Beneath the Sea: Submarine Conflict 1939–1945, John Murray, London, 1995, p. 21. Ibid., p. 24. Author conversation with Admiral McGeoch, 6 Sept. 2000. Admiral McGeoch’s paper survives in IWM P/347. Karl Dönitz, Die U-bootwaffe, E.S.Mittler, Berlin, 1939. Translation taken from CHURCH ROSK 4/92. PRO AIR 15/34, Trade Protection—Convoy Organisation, 1939. PRO ADM 239/126, Mercantile Convoy Instructions, 1934. David Henry, ‘British Submarine Policy’, in Bryan Ranft (ed.), Technical Change and British Naval Policy 1860–1939, Hodder & Stoughton, London, 1977, p. 93. The U-boat War in the Atlantic 1939–1945, German Naval Staff History, HMSO, London, 1989, p. 4. Although a submarine working in to attack from the dived danger area would have to use its periscope, so presenting a counter-detection opportunity, visual detection of a periscope from a ship is, at best, a haphazard business, and even the early asdic sets presented a more reliable means of detection. Visual detection of dived submarines from the air could, likewise, not be relied on. This must have caused considerable embarrassment to the Commander of the Achilles, Cdr P.F.Cooper, who was one of the navy’s most senior A/S specialists! PRO ADM 186/155, CB 1769/34(1). PRO ADM 186/155, CB 1769/34(2). PRO ADM 186/106, CB 01821, Battle Instructions, June 1928. PRO ADM 186/153, CB 1769/33(1) and 186/515, CB 3002/34. PRO ADM 186/143, CB 1769/27(2). PRO ADM 186/157, CB 1769/35. PRO ADM 186/143, CB 1796/27(2). PRO ADM 186/158, CB 1769/34. PRO ADM 186/1769/32(1). PRO CAB 4/26, CID 1318-B, Defence Against Submarine Attack, March 1937, p. 4. PRO ADM 116/3635, Minutes of 2nd meeting of the Shipping Defence Advisory Committee, 31 July 1937. PRO ADM 1/8765/313, Cruiser Policy: Proposals for Smaller Cruisers and Minutes of the Naval Planning Committee. Martin Doughty, Merchant Shipping and War: A Study in Defence Planning in the Twentieth Century, Royal Historical Society, London, 1982, provides an excellent analysis of the efforts made to prepare the mercantile marine, ports and distribution systems for a wartime attack on trade. PRO AIR 2/3101, Coastal Command Plans for Reconnaissance, Convoy Escort and AntiSubmarine, 19 Dec. 1938. Hague, Convoy, p. 23. Author conversation with Admiral McGeoch, 6 Sept. 2000. PRO ADM 186/468, CB 3002(28), p. 36. PRO ADM 186/143, CB 1769/27(2). PRO ADM 186/476, CB 3002/29. PRO ADM 186/491, CB 3002(31).


TACTICS 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111

PRO ADM 1/9341, Staff Requirement for Asdic Sloops, 21 June 1932. PRO ADM 1/9424, Escort Vessels—Staff Requirements, 17 Feb. 1937. PRO CAB 4/26, Defence Against Submarine Attack, 24 March 1937, para. 16. Author conversation with Admiral McGeoch, 6 Sept. 2000. PRO ADM 186/515, CB 3002/34. PRO ADM 1/8672/230, Construction Programme, Light Cruisers, Destroyers, Minelayers etc., 1924. PRO ADM 186/66, Naval War Manual, 1925. PRO ADM 116/2410, A/S Depot Portland, Letter dated 10 Oct. 1927. PRO ADM 1/1214, A/S Striking Forces, D of TD memo dated 13 April 1938. PRO AIR 15/38, Air Tactics, A/S Operations, 1938. PRO ADM 1/12141, Anti-Submarine Striking Forces, Memo written by Capt. Budgen, an ex-Capt. A/S, 13 April 1938. PRO ADM 186/468, CB 3002(28), p. 25. PRO ADM 186/157, CB 1769/35. Ibid. Ibid. Ibid. PRO AIR 15/38, Air Tactics, A/S Operations, Notes on exercise XTF, 6–7 Dec. 1938. PRO ADM 1/12140, A/S Policy, TD memo, ‘Provision and Training of A/S Personnel’, 14 June 1937. PRO ADM 186/459, CB 01793, Portland Experimental Section Quarterly Report, 30 June 1928. PRO ADM 186/455, CB 01793, Portland Experimental Section Quarterly Reports, 30 June 1927 and 31 Dec. 1927. PRO ADM 186/491, CB 3002/31. PRO ADM 186/465, CB 01793, Portland Experimental Section Quarterly Report, 31 March 1929.


7

Wartime Experience

In order to put inter-war A/S developments into some sort of perspective, and see just how effective anti-submarine measures were, this chapter will touch on the early days of the Battle of the Atlantic. Enough dramatic and informative accounts have been written about that great conflict already, and this is in no way meant to be a short general history. Instead, individual U-boat versus anti-submarine vessel actions have been analysed as fully as possible to see how well they reflected what was expected to happen, and how effective the anti-submarine vessels actually were when they got within sniffing distance of a submarine. An attempt to construct such a narrative for the whole war would take over the book. This study has therefore been stopped in June 1940 because, first, however good the pre-war preparations, tactics and procedures evolve when tested in action, and after the middle of 1940 the modus operandi of the anti-submarine forces diverged from that employed in the early days to such an extent that examination of later actions would not help us assess the pre-war work. Second, from the late summer of 1940 U-boats operated from the French Atlantic ports. Portland had prepared for attack from single submarines working in the relatively shallow waters around the UK, in which conditions a depth charge set at 100 feet or 150 feet would have a fair chance of at least damaging a submarine, and determination of submarine depth was not a major factor. The tactics and sensors required to defend against a multiple U-boat attack in the deep waters of the mid-Atlantic were so different that is seems hardly fair to judge the pre-war preparations against the pack attacks that came after the summer of 1940. In the preparation of this chapter, information has been taken from published sources, private papers, ships’ logs and reports of proceedings to give as clear an account as possible of every significant or instructional interaction between U-boats and anti-submarine forces between the outbreak of war and the end of May 1940. Regrettably, all destroyer logs which originated after January 1940 have been destroyed, so this vital source


WARTIME EXPERIENCE

of information has been denied to the historian.While the collections from before that date are far from complete, the reader may notice that narratives of earlier actions are necessarily more complete than those of actions after the end of that month. WARSHIP AND TROOPSHIP DEFENCE On 14 September 1939 HMS Ark Royal, in company with her escorting destroyers, HM Ships Faulknor, Foxhound and Firedrake, was conducting offensive anti-submarine operations to the west of the Hebrides when she was attacked by U-39.1 The boat, commanded by KL Gerhard Glattes, was on passage to Wilhelmshaven at the time, and appears to have sighted the carrier purely by chance. Although not flying at the time, Ark Royal was steaming at speed so the escorts were going too fast for their asdic to be fully effective. Also, oddly for a force which was not engaged in flying, the force was not zigzagging, so provided he was within the dived danger area the submariner would not have had a particularly difficult approach. Blair has the destroyers 4 nautical miles away from the carrier at the time of the attack, which was certainly further than they should have been according to Portland doctrine. He believes that this was due to the carrier ‘falling behind’ while conducting flying operations, which would seem odd as it was the escort commander’s responsibility to keep his ships in station on the carrier, whatever she did. The author does have personal experience of modern carriers turning in unexpected directions and increasing speed without warning, making it very difficult for the escort to stay in station, particularly if running on an engine configuration which does not allow maximum speed to be rapidly achieved. In Ark Royal’s case, however, all three destroyers had been steaming on a steady course at 24 knots ever since flying operations had been completed, an hour before the attack, so doubt must be cast on Blair’s assertion. In any event, the attack failed, the torpedoes exploding some hundreds of yards from their target, and the escorts slowed down to close the believed position of the submarine, where they commenced a classic Portland hunt. The logs of all three escorts survive, and although many of the timings shown are contradictory, it seems clear that the submarine was rapidly detected and depth-charged. The initial attack by Foxhound damaged the boat’s electrical systems, and the follow-on attacks by the other two escorts forced the boat to the surface, where it was engaged by guns. Some 40 minutes after firing her torpedoes U-39 was on her way to the bottom, the first U-boat to be lost in action, and her crew were in the water, later to be taken to the Tower of London. Steaming at speed in a straight line, with asdic ineffective but all ships making enough noise to be detected by the submarine’s hydrophones, was 163 Copyright © 2003 George Franklin


not an activity in accordance with the normal anti-submarine doctrine, but would seem to have been forced by circumstances. It is unlikely that their asdic domes were retracted, but the flow noise from the water passing the hull and the dome would have masked all but the strongest echoes. The submariner would have been extremely reluctant to use his periscope for fear of being spotted by aircraft, but could have made most of his approach using hydrophones. The force commander thus had to accept the risk that if a submarine found itself within the narrow dived danger area ahead of a ship steaming at 24 knots he would have a good chance of making an attack. It does seem, however, that the escorts were distributed over a wider front than was necessary to cover only the dived danger area, so with better positioning might have been able to detect the submarine before its attack, notwithstanding the degraded performance of their asdic. Once the submariner had revealed his presence by attacking, a hunt was initiated in accordance with the doctrine and the submarine was destroyed. U-29, commanded by KL Otto Schuhart, was nearing the end of an already successful patrol when, on 17 September, she happened across the carrier HMS Courageous which was engaged in anti-submarine patrol. The carrier was in company with two of her four escort destroyers, the other two having parted company to assist a merchantman.2 Schuhart tried to work himself into a firing position, but as he was outside the dived danger area he was unable to do this, and after an hour he had only succeeded in closing the range from 10,000 to 7,000 yards. He estimated the carrier to be making 20 knots, and all he could do was attempt to stay in touch. After a further 20 minutes the carrier suddenly altered course by 70 degrees towards him and reduced speed, so putting him in an ideal position to attack. One of the two escorting destroyers is reported to have passed within 500 yards of the approaching submarine without having detected it, so it is unlikely that a fuller screen would have hindered the attack. Two of the three torpedoes hit home and the carrier sank. The submarine was subsequently detected by the escort, and reported having been heavily depthcharged, Schuhart at one stage believing that his boat was about to be crippled, but they eventually got away. Again, as in the case of the Ark Royal, the initial approach and attack had been made undetected, but once the escorts were alerted to the presence of a submarine they were able to make asdic contact and press home attacks. Following the air raid on Scapa Flow on the night of 16 March, the German Naval Staff concluded that the Home Fleet would put to sea, possibly returning to the relative safety of the west coast. Anticipating this movement, four U-boats were stationed to the west of the Pentland Firth to intercept the heavy units when they exited the anchorage.The only one of these boats to have any contact was U-44, commanded by KL Ludwig Mathes, who had sent eight merchant ships to the bottom on his previous patrol. While attempting to attack a battle cruiser ahead of the fleet, the 164 Copyright © 2003 George Franklin

WARTIME EXPERIENCE

boat was detected and sunk by the screening destroyer HMS Fortune.3 Fortune was acting as part of the fleet’s screen, and it seems likely that the submarine was detected and sunk while attempting to penetrate the screen, so had not yet made its attack. There were no survivors, the boat going straight to the bottom, and wartime records do not include the action. It is safe, therefore, to conclude that as far as Fortune was concerned, all she knew was that she had attacked what seemed like a U-boat, and after some attacks the contact disappeared. In fact, in accordance with Portland screening doctrine, she had detected a boat, prosecuted it and destroyed it. The first part of the British expeditionary force to Norway left the Clyde and Scapa in the heavily escorted and extremely valuable troop convoy NP1. The passage went largely without incident,but as the convoy approached the Norwegian coast on 15 April it was reported that a U-boat had been sighted from the shore. HM Ships Fearless and Brazen, two of the nine escorting destroyers, were despatched ahead to hunt, Fearless gaining initial asdic contact at a range of 1,700 yards. A brief hunt followed, and after the first depth charge attack the boat, which turned out to be U-49 under the command of KL Curt von Gosler, ‘shot to the surface’ and was subsequently destroyed. Once again, an accurate sighting report had localised the position of a U-boat, enabling a pair of destroyers to initiate a successful Portland-style hunt. This attack proved especially fruitful as details of the U-boat dispositions for the invasion of Norway were recovered from the floating debris left by the submarine. The U-boat arm was severely dogged throughout the Norwegian campaign by torpedo failures, so the number of recorded and, for the purposes of this study, useful interactions is low. Of note, though, is that in a number of cases U-boats were able to penetrate screens undetected to make attacks on heavy units, HMS Warspite in particular being saved on at least three occasions by torpedo failures. In those attacks during which torpedoes did not explode, the U-boats generally remained undetected, while an exploding torpedo, whether under its target or harmlessly in open ocean, would often lead to asdic contact and, at least, damage to the boat. One can conclude that, in general, submarines fortunate enough to find themselves inside the dived danger area of even a heavily defended force were able to make their first approach with relative impunity. Once alerted to their presence, however, escorts were usually able to detect and prosecute them with asdic, at least driving them off and usually damaging or sinking the boats. CONVOY DEFENCE Any attempt to construct firm statistics about convoyed merchant ships is fraught with difficulties as convoys did not all passage together from one port to another. Some assembled at sea, many dispersed at sea, most had ships 165 Copyright © 2003 George Franklin


which ‘straggled’ behind, some had ships which ‘romped’ ahead, and escort from end to end was very far from being guaranteed. For the purposes of this section the Admiralty definition of ‘one or more merchant ships or auxiliaries sailing under the protection of one or more warships’ has been adopted. Thus unescorted convoys, convoys which had dispersed when the action took place, and ships which were separated from the escort, will not be considered.As the book is concerned primarily with asdic-related tactics, convoys escorted by non-asdic-fitted ships will not be considered either. The first source to which one naturally turns is the Naval Staff History;4 this however includes stragglers in its figures. Numerous books and records have been published since 1945 showing details of merchant ship sinkings, few of which agree with each other, but probably the most reliable, and certainly the most recent, is Arnold Hague’s,5 which represents some 50 years of research. The method adopted, therefore, has been to use his information as a baseline but to check all information against Kenneth Wynn’s near definitive U-boat history,6 the British Naval Staff History and the German Naval Staff History.7 A number of primary documents have also been consulted, including ADM 53 series of ships’ logs and ADM 199, 217 and 237 series of convoy records and escort reports of proceedings. Where no discrepancy is highlighted, these sources can be assumed to have been in agreement on the relevant details. Hague’s listing of ‘losses incurred in convoy, excluding stragglers’ details the sinkings for the period between the outbreak of war and the end of May 1940 and indicates that German U-boats sank 14 allied or neutral merchant ships in allied convoys over the period. Thus, German U-boats sank 14 allied or neutral merchant ships in allied convoys between the outbreak of the war and the end of May 1940. A close examination of each sinking indicates the efficacy and relevance of the Portland doctrine and training. The first three ships pose no problem at all for analysis, as the convoy was not escorted when attacked, and scattered after the first attack. A local escort had been provided on departure from Gibraltar, and it was planned to provide another escort as it entered the western approaches, but none was in the area when U-46 sank SS Yorkshire, its first victim. HM Ships Escort, Electra and Wakeful were despatched to the scene but did not arrive with the reassembling convoy until the following day. For completeness of evidence it should be noted that Blair8 describes this convoy as having been ‘heavily escorted by British destroyers transferring from the Mediterranean to home waters’, but the reports of proceedings9 make it clear that the convoy was not escorted between the departure of the local Gibraltar escort during the night 13–14 October and the arrival of Escort and Electra on 18 October. The convoy was thus unescorted when attacked on 17 October. The next ship, SS Malabar, was escorted by two destroyers, HM Ships 166 Copyright © 2003 George Franklin

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Grafton and Gallant. The escorts’ logs, which would normally be the best record of an inconclusive anti-submarine action, do not survive, but there is nowhere any indication that they gained contact on the submarine. This action, then, can be taken to be a square failure of the anti-submarine escort. SS Bronte, although listed as having sunk on 30 October, was actually attacked early in the morning three days before. The convoy had an escort of two destroyers, HM Ships Walpole and Whirlwind, both of which gained good contact on a submerged object, before attacking using patterns of five depth charges.The only evidence of success was an oil slick and bubbles on the surface, and the surviving U-boat records do not indicate that U-34 was damaged in the attack. Indeed, she went on to attack Malabar two days later and, given that U-boats frequently released oil and air to simulate a hit, one can conclude that, again, the escorts failed to achieve any positive result. Even if the oil was deliberately released, however, this would indicate that the destroyers were at least attacking the U-boat, rather than a false contact, so preventing it from making another attack on the convoy. SS Royston Grange was sunk in similar circumstances and the two escorting destroyers, HM Ships Versatile and Witherington, detected and prosecuted a contact which let out oil and water after being attacked.The hunt continued from 1320 until 1655 hours, a total of 15 depth charges being dropped in four attacks on U-28. Again, there is no evidence of significant damage to the U-boat, which went on to lay mines off Swansea and returned to base on 18 December.There is no doubt, however, that the U-boat was prevented from taking further action against the convoy. SS Navasota was sunk in a homebound convoy not far east of the line where they were usually joined by their escorts. HMS Escapade was ‘in the vicinity’, and half an hour after the attack she ‘attacked a very poor contact with no results’.The reader will remember that when a single ship made an attack she necessarily lost contact, and following her attack Escapade is reported to have ‘failed to regain contact in a very big sea’. The attack on the submarine is reported to have been ‘desultory’.10 Some hours later, when she had ceased hunting and taken station on the convoy, she was joined by HMS Walpole. MV Vaclite was sunk at seven o’clock in the morning while, apparently, in convoy OA 80 G. The escorting vessels, HM Ships Fowey and Whitshed, whose logs survive, make no mention in those documents of her sinking. This indicates very strongly that either Vaclite or the escorts were not with the convoy at the time. Roskill tells us that the convoy had been placed in some disarray by bad weather,11 and it seems likely that Vaclite and the escort were not in company at the time of the sinking. Having sunk Vaclite with impunity, KL Werner Heidl in U-55 returned four hours later to attack again, this time sinking the SS Keramiai. On this occasion she was not so fortunate; she was immediately detected by Fowey, 167 Copyright © 2003 George Franklin


who was soon joined by Whitshed, the other escort, and 17 minutes after hitting the Keramiai the U-boat suffered her first depth charge attack. In a familiar pattern, the destroyers saw oil and water on the surface but after several attacks disengaged. On this occasion, however, the U-boat was damaged and forced to the surface, where she was detected by a Sunderland flying boat of 228 Squadron.The Sunderland and the two escorts reengaged the submarine, which was then scuttled by Heidl, who appears to have ensured that his crew were clear before sinking the boat, from which he did not escape. The SS Armanistan was sunk while in a convoy which was being escorted by non-asdic-fitted French ships, so does not enter our statistics. SS Beaverburn was sunk while in a convoy with an escort of only one destroyer, HMS Antelope, which detected the submarine soon after it had attacked.The destroyer then conducted an 11-hour hunt, during which 21 depth charges were fired in six attacks and at the end of which U-41 was destroyed, all hands being lost. SS Pyrrhus, like the Armanistan, was being escorted by two French vessels which did not have asdic equipment. Further, the convoy had substantially scattered in heavy weather so the French escorts were not able to provide proper protection.The Commodore of the convoy in fact reported that he did not see the escorts at all on the day the Pyrrhus was sunk. Although Hague lists SS British Endeavour as having been sunk while in convoy, both the First Sea Lord’s daily intelligence summary and the Naval Staff ’s contemporary record state that, in company with one other merchant ship, she had fallen well astern of the convoy during the previous night. Hague highlights a difficulty of definition in that the commanders at sea tended to call any ship which had detached from the convoy a straggler, while the Naval Staff, and Hague, define a straggler as a ship ‘that has definitely become separated from a convoy and is out of sight of her convoy and all escorting vessels’.12 It can thus be taken that, when she was torpedoed, the British Endeavour was within sight of the tail end of the convoy but beyond the range at which the escort could reasonably provide protection or commence an effective hunt. SS Orangemoor was attacked and sunk while being escorted by HMS Arabis, a newly constructed Flower class corvette. Arabis detected the boat and pressed her attack home. Roskill13 states that U-101 was slightly damaged in this attack, and his original notes give this information as well14 but provide no indication of his original source. Certainly the damage cannot have been severe as U-101 went on to sink another five merchant ships before returning to base a month later. In any event, however, the Arabis undoubtedly prevented the submariner from putting in further attacks on that convoy.


WARTIME EXPERIENCE

In conclusion, then, up to the end of May 1940, a total of six merchant ships were sunk by U-boats while in convoys with asdic-fitted escorts. Of these six sinkings, two led to the destruction of the U-boat, three led to the U-boat being detected and attacked with possible damage being inflicted, and in only one case did the U-boat escape without being detected on asdic. In none of these cases was the submarine able to press home a second attack on the convoy.To put these statistics into proportion, U-boats sank a total of 72 merchant ships during this period.The information provided by Hague, subject to close analysis, can thus be presented as shown in Table 8.

Table 8: Ships Sunk in Convoys, 3 September 1939–31 May 1940



There were of course, over this period, other interactions between Uboats and merchantmen which resulted in loss of or damage to the submarines, some of which are worthy of report. One of the earliest such came when HM Ships Imogen and Ilex were in the vicinity of the SS Stonepool, which had straggled from convoy OB 17. Accounts of this action are contradictory. Wynn reports that the submarine attacked the merchantman with gunfire but was met with return fire which forced the boat to dive and damaged her steering gear. When she resurfaced the two destroyers appeared and she was easily sunk.15 According to the diary of the first lieutenant of Imogen, Stonepool’s lookout saw the boat, which was reported to the destroyers, then some seven miles distant. On closing, Imogen gained asdic contact and became directing ship. Ilex then gained contact and pressed home a five-charge attack, following which the boat came to the surface and both ships engaged it with gunfire, Ilex ramming.16 This version is backed up by surviving anti-submarine division papers,17 and Blair’s account, which also specifies that the depth charges ruptured the submarine’s stern ballast tanks, forcing the CO into an emergency surface to save the boat.18 On 31 May, the last day of the period under study, OL Max Schulte in U-13 was working his way in to attack an east coast convoy when the sloop HMS Weston, the convoy’s sole escort, saw the submarine against the sunset and closed to hunt.The boat dived but was detected on asdic. In the following hunt the sloop’s CO, Lieutenant-Commander S.C.Tuke, showed remarkable tenacity, dropping a total of 31 charges in five attacks, losing contact on every attack but managing to regain each time, eventually destroying the submarine. A 1940 review drew one conclusion which coincided with the pre-war Portland doctrine and one which modified it: It must not be supposed that an escort provides physical protection to a convoy; to do this the number of escorting vessels would, in most cases, have to exceed the number of ships in convoy… It is therefore of utmost importance that escorts should be operated offensively and that any U-boat which attacks a convoy should be hunted relentlessly until destroyed.19 The latter part of this statement highlighted the only real discrepancy between pre-war assessments and wartime tactics, which was brought out in the aftermath of the attack on the merchant ship SS Teakwood on 21 September 1939.20 Teakwood was in a convoy being escorted by HM Ships Acasta and Ardent, one of which was on each bow of the convoy, when the merchant ship was torpedoed but not sunk by a single torpedo fired by KL Gerhard Glattes in U-35. Ardent immediately altered towards the stricken ship while Acasta commenced an asdic search around the convoy. After searching in Teakwood’s immediate vicinity Ardent took some men off and detached from the convoy with the intention of 170 Copyright © 2003 George Franklin

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escorting Teakwood to safety. Some 15 minutes later she obtained a moderate asdic contact and fired a single charge. Contact was lost and she continued on her way with Teakwood. She was not to know it, but she had successfully detected the boat and caused sufficient damage for the submarine to have to sit on the seabed for some hours effecting repairs. The CO of Ardent was roundly condemned for not continuing the hunt: It is clear that the CO failed to pay attention to the imperative need for seizing every opportunity for destruction of enemy submarines.21 To those officers whose employment has so far been mainly on submarine hunting operations the golden opportunity of a submarine being definitely within striking distance is so evident as to leave no shadow of doubt. To those whose work has been exclusively with convoys, the responsibility for ‘safe and timely arrival’ may have affected their judgement.22 The C in C Plymouth noted that he had interviewed the CO and that ‘he is now, however, quite clear as to what his duty is’. Not, one imagines, an entertaining interview for the CO! Here we see the difference between the pre-war doctrine, under which a submarine abaft the limiting lines, no longer presenting a threat, could be left alone, and the overarching wartime requirement to prosecute submarines whenever the opportunity arose. OFFENSIVE PATROL Although the majority of the events described here did involve ships on offensive patrol, this section has also been used to sweep up some other actions.We will thus be examining here engagements by a ship that was close to, but not escorting, a convoy and by a ship that was on transit, together with other similar, almost chance encounters. On 14 September, aircraft from Ark Royal, engaged in anti-submarine patrols, sighted U-30, commanded by KL Julius Lemp, infamous for sinking the passenger ship Athenia on the first day of the war. The boat was attacked, without success, by Swordfish and Skuas.Two of the Skuas, which appear to have conducted their bombing run at very low altitude, actually had to ditch owing to damage caused by their own bombs, and Lemp surfaced to rescue the airmen, only to be strafed by another aircraft. The remaining aircraft, as well as causing damage in a second strafing attack, were able to transmit a good positional report and three destroyers were ordered to close the position. The two which were detailed to hunt the submarine found it and conducted a number of attacks during which dials were shattered and cracks appeared in the torpedo tubes and the engine room. The boat, however, managed to escape after six hours. 171 Copyright © 2003 George Franklin


Vice-Admiral Sir Alastair Ewing, who was, during the early months of the war, first lieutenant of HMS Imogen, kept a very detailed diary which allows us some interesting glimpses into the beliefs of the time.23 On 15 September, the day after Ark Royal’s aircraft and attached destroyers had attacked U-30, Ewing’s destroyer was in company with the carrier HMS Hermes carrying out anti-submarine sweeps. One of the aircraft signalled that it believed it had spotted a submarine but the destroyers were not sent to prosecute the submarine, instead being kept close for protection of the carrier.This policy would have rendered the entire carrier group sweeping operation useless as it was only by detaching destroyers to prosecute submarines that there was any chance of sinking the submarines. The following day the carrier signalled to its escorts that, if an aircraft spotted a submarine, three of the destroyers were to detach to search, the fourth remaining with the carrier to screen. A day later HMS Courageous was sunk; the reader will remember that two of her four escorts had been detached to assist a merchantman. In reaction to the sinking of HMS Courageous, the Hermes made a further signal stating that ‘Ships are not to part company without orders or act on aircraft reports.Two destroyers only will be sent if prospects appear favourable.’ Some days later, seemingly under Cabinet pressure, the First Sea Lord instructed that aircraft carriers were no longer to be employed in antisubmarine hunting operations.24 Admiral Forbes, then Commander-in-Chief Home Fleet, although well aware of the risks that such operations held for his ships, felt this to be an error. He wrote to Roskill some time after the war that ‘I was told by the Admiralty not to use the Ark Royal for hunting submarines again which nearly broke my heart as I was of the opinion that aircraft [with] destroyers with Asdic was the method of sinking U-boats.’25 Aside from the sinking of U-39, which for our purposes has been considered as an action in defence of a warship, albeit that that warship was engaged in an offensive patrol, the first success enjoyed by surface attack groups was that of HM Ships Fortune and Forester which sank KL Johannes Franz’s U-27 on 20 September. The ships had been directed to the vicinity of a reported U-boat,26 but as they closed the area they were seen by the boat. As it was approaching midnight Franz decided to make a surfaced attack on the destroyers, but his attack failed, the torpedoes either missing or detonating early. Almost immediately the destroyers saw the boat, which dived, but the destroyers gained early asdic contact.The ensuing hunt lasted nearly four hours, during which time the ships carried out five attacks, each one using a full pattern of five charges, and after the final attack the boat was forced to the surface. This action followed the classic Portland pattern in which destroyers start with the advantage of good positional information, in this instance one of them seeing the boat on the surface, and hunt the boat to destruction. The next success by a patrol group came on 14 October when HM 172 Copyright © 2003 George Franklin

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Ships Inglefield, Ivanhoe, Icarus and Intrepid were on patrol in south-western approaches.27 Having left Plymouth the previous evening, they received a report from a merchant vessel that she was being chased by a submarine. On closing the position, at around 1010, Inglefield saw the submarine on the surface. Almost exactly as U-27 had done, U-45 dived and was hunted by the four destroyers. Again, several attacks were made, and, with only wreckage coming to the top, U-45 was later assessed to have been sunk with all hands. Two contrary arguments come out of this engagement: the first is that if there had been no patrol in the area the U-boat would probably have succeeded in sinking the merchantman; the second is that if the merchantman had been part of an escorted convoy the problem might not have arisen in the first place. Early in the morning of 29 November HMS Icarus was in the North Sea attempting to round up the convoy, which she had been escorting the previous day and which had become scattered, when she sighted a U-boat against the rising sun.28 She closed rapidly, gained an asdic contact and attacked with one pattern of five charges. She judged the attack to have been unsuccessful, but was unable to follow it up as her asdic set became defective. She remained in the area, however, until Kingston and Kashmiri, which had been on patrol close by, arrived some three hours later, upon which she left the scene to rejoin her convoy. The two new joiners soon gained an asdic contact and attacked, damaging the boat and forcing it to the surface. U-35 finally sank, but KL Werner Lott and all 43 of his crew were captured. It seems likely that Lott was still in the area as he was following the current U-boat doctrine of going to the bottom and remaining silent when attacked, which was based on the belief that asdic was a passive listening device rather than an active search tool. Once again, a patrol group was able to claim a success, but only against a submarine which had previously been detected by a means other than asdic. There is an amusing sideline to the capture of Lett’s crew, which tells of how Lott threatened to go on hunger strike in protest at the cold in his Tower of London cell. Captain The Lord Louis Mountbatten, who commanded the flotilla which included Kingston and Kashmiri, interviewed Lott and arranged for his complaint to be resolved. By way of an apology, Lott and his second-in-command were taken, in civilian clothes and at Admiralty expense, to Scott’s restaurant in London. After a very fine dinner with two RN officers of Lett’s previous acquaintance, the Germans were returned to their, suitably warmed, cells. HMS Gleaner, an asdic-fitted minesweeper, was on patrol inside the Clyde during the night of 11/12 February when, at 0350, she saw a periscope wash in her searchlight. She turned to search, and at a range of 3,000 yards gained contact on U-33, commanded by Hans Wilhelm von Dresky, which had been attempting to lay mines. During the ensuing hunt, which lasted over two hours, Gleaner dropped a total of ten depth charges in three attacks, 173 Copyright © 2003 George Franklin


the last of which put her own asdic out of action and forced the U-boat to the surface. Seventeen of her crew were captured, the remainder, including von Dresky, being lost, and some enigma rotors were recovered. Dönitz is reported to have decided after this action that he considered minelaying in such confined waters should be stopped as it was too hazardous for the submarines.The Gleaner/ U-33 action is of particular interest as the boat is reported to have been employing the then current anti-asdic tactic of sitting on the bottom when Gleaner gained contact. This shows that asdic was effective in picking out a boat against background returns from the bottom, and that the German tactics were fundamentally mistaken. HMS Gurkha appears to have been on passage on 24 February when she saw U-53 on the surface at close range. An initial attempt to ram failed, and as the boat dived Gurkha dropped a pattern of charges based on a visual reckoning of the submarine’s position. The destroyer then gained asdic contact and conducted three more attacks, after which contact was lost. The submarine never returned home, and is assumed to have sunk with all hands in 1,800 feet of water. There are many recorded instances of Coastal Command aircraft on patrol sighting submarines on the surface,29 notably in the North Sea. As the aircraft themselves were not fitted with an effective weapon, and there was a paucity of surface escorts, very few of these encounters ended with the submarines being damaged.The problem seems to have been that the U-boat was generally able to react quickly to the arrival of aircraft on the scene, so that by the time the pilot had manoeuvred into a bombing position the boat had dived.The airmen thus had to project forward along the wake left before diving, and aim bombs at an estimated position, or if they were fortunate they might have a periscope to aim at. The accuracy of such bombing was predictably poor, and the effectiveness of the bombs against a dived target was very limited anyway. Admiral Talbot, reviewing the situation in February 1940, concluded that ‘it is essential that fast striking forces should be provided for the Northern part of the North Sea, as soon as possible’30 in order to work with the aircraft and take full advantage of the sightings which were being achieved. This plea, while self-evidently justified, was easier to make than to fulfil, and initially it was met by the formation of trawler attack groups in the Orkneys and Shetlands, which were able to work with patrolling aircraft to provide a more realistic threat to passaging submarines. No great success in U-boat killing was enjoyed by these groups, however, and a detailed study of their activities falls outside the scope of this book. Another, more obvious, solution to the problem of unifying the efforts of ships and aircraft was to use ships with aircraft on them.While this policy, of sending carriers to sea with groups of destroyers to conduct offensive operations, did enjoy some success, it was decided early that the risk to the carriers was too great and, as we have already seen, it was discontinued before the war was many weeks old. 174 Copyright © 2003 George Franklin

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NOTES 1

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

30

Stephen Roskill, The War at Sea, HMSO, London, 1956, Vol. 1, p. 68; Kenneth Wynn, U-Boat Operations of the Second World War, 2 vols, Chatham Publishing, London, 1997, p. 28; Clay Blair, Hitler’s U-boat War: The Hunters, 1939–1942, Weidenfeld & Nicolson, London, 1997; PRO ADM 53/108689, Firedrake log, ADM 53/108783, Foxhound log, ADM 53/108656, Faulknor log, ADM 53/107522, Ark Royal log. CHURCH ROSK 4/92 and ROSK 6/5; Roskill, War at Sea, Vol. 1, pp. 105–105; Wynn, U-boat Operations; Blair, U-Boat War, pp. 88–90. Roskill, War at Sea; Wynn, U-boat Operations; and The U-boat War in the Atlantic 1939– 1945, German Naval Staff History, HMSO, London, 1989. The Defeat of the Enemy Attack on Shipping, 1939–1945, originally CB 3304 (1A), Navy Records Society, Aldershot, 1997. Arnold Hague, The Allied Convoy System 1939–1945: Its Organisation, Defence and Operation, Chatham, London, 2000. Wynn, U-boat Operations. German Naval History. Blair, U-boat War, p. 113. PRO ADM 116/3809, Reports on HG convoys. Blair, U-boat War, p. 120. Roskill, War at Sea, Vol. 1, p. 129. Hague, Convoy, p. 16. Roskill, War at Sea, Vol. 1, p. 133. CHURCH ROSK 4/92. Wynn, U-boat Operations, p. 29. IWM DS/MISC/31, Diary of Vice-Admiral Sir Alastair Ewing. CHURCH FWCT 2/4/7a, ‘Reports of Successful Attacks on U-boats’, kept in the personal papers of Cdr Fawcett, who was at the time in the A/S division. Blair, U-boat War, p. 112. IWM, Memoirs of Vice-Admiral Sir A.G.Talbot, CB, DSO, Paper entitled ‘Review of Methods of Dealing with the U-boat Menace’, Feb. 1940. PRO ADM 199/62, Reports on Convoys, and ADM 53/107294, HMS Acasta log. Cdr P.J.Oliver in ADM 199/62. Capt. C.Caslon, Capt. D 18 in ADM 199/62. IWM, DS/MISC/31, Diary of Vice-Admiral Sir Alastair Ewing. Roskill, War at Sea, Vol. 1, p. 106. CHURCH ROSK 6/30, Letter from Forbes to Roskill, 10 Feb. 1950. CHURCH FWCT 2/4/7a, ‘Reports of Successful Attacks on U-boats’. Roskill, War at Sea; Wynn, U-boat Operations; PRO ADM 53/109305, Inglefield log, PRO ADM 53/109348, Ivanhoe log. Roskill, War at Sea; Wynn, U-boat Operations; CHURCH FWCT 2/4/7a, PRO ADM 53 109255, Icarus log. PRO AIR 2/2925, Attacks by Aircraft on Enemy Submarines, reports 9/9/39 to 1941, lists 82 such attacks between the outbreak of war and the end of May 1940, none of which resulted in sinking or severe damage to a submarine. IWM, Papers of Vice-Admiral A.G.Talbot, CBDSO, ‘Review of Methods of Dealing with the U-boat Menace’, Feb. 1940.


8

The System

Having looked, on a thematic basis, at the different parts of the British anti-submarine warfare system, the intention here is to take a chronological approach, tying in many of the issues already discussed, but highlighting their interrelation, and the way the whole system evolved over time. The early post-armistice years were the period of greatest optimism in A/S, advances in asdic coming on top of the fact that the German submarine campaign had been defeated by convoy Roskill writes of ‘euphoria among the Board of Admiralty’ and quotes Chatfield, then Assistant Chief of the Naval Staff, as telling his colleagues that ‘we have got to the stage when the hitherto “undetectable craft” is detectable…the time is coming when we shall have to rebalance our theories as to the tactical use of submarines’.1 This state of affairs was particularly pleasing as there was at the time no real submarine threat to the Empire. There remained, however, an awareness that trade routes and naval forces could theoretically be susceptible to attack, and Beatty, as First Sea Lord, insisted that ‘the pressing forward with experiments in Asdics is of the first importance’.2 With the development of a tangible naval threat in the Far East, the planners started to consider the use that might be made of submarines against British shipping. Their conclusion was that the Japanese were most likely to use their boats to attack elements of the Battle Fleet, so defence of naval units became the priority. Their protection in harbour would be afforded by the rapidly developing Mobile Naval Base Defence Organisation, and destroyer screens would provide defence at sea. We thus see the introduction in 1922 of the first operational destroyer set, the type 114, followed a year later by another set, the type 115. In 1923 and 1924 the sixth destroyer flotilla was the first operational formation to receive asdic equipment, and all the initial tactical trials were aimed at defence of the fleet. With the introduction of asdic to fleet flotillas came a realisation that responsibility for this new, complex and potentially vital equipment should no longer lie with generalist torpedo officers. The outline for an officer’s branch was thus established in 1922, and the following year the first true


THE SYSTEM

specialists completed their six-month training course. Six of them stayed at HMS Osprey to form the core of the training, trials and tactical development organisation, two joined 1 A/S to become the seagoing part of that organisation, and Lieutenant-Commander P.A.Maitland took the good news to the wider world as anti-submarine officer to the Captain of the sixth destroyer flotilla. In 1925 the second destroyer flotilla, part of the Mediterranean Fleet, was also fitted with asdic, and in that year investigations started in earnest into the employment of aircraft in support of asdic-fitted ships. Ratings and officers, meanwhile, were being trained at Portland to man the increasing number of asdic-fitted ships. The depth charge, essentially unchanged since the armistice, was still the only effective weapon against dived submarines. Growing awareness, however, of the conflict between a sensor with a minimum range of some hundreds of yards, and a weapon that had to be launched over the stern of the ship, was driving research into ahead thrown weapons. It was becoming evident that the relatively ad hoc organisation, which had emerged from post-war contraction of both the uniformed and scientific wings of the service, was no longer adequate to manage this rapidly growing capability. Various proposals were therefore made as to the shape and size of the rationalised organisation. An experienced admiral was appointed to head a committee of investigation, and the outcome was the development of an infrastructure that covered the Mining and Torpedo Establishment and the Signal School, both at Portsmouth, the Admiralty Research Laboratory at Teddington and the A/S Establishment at Portland. Captain A/S, who assumed overall responsibility, would stay at Portland, which was confirmed as the central training establishment, the Alma Mater of the branch, the base port of 1 A/S and the general point of reference for all things anti-submarine. 1928 saw a consolidation of the ratings’ Submarine Detector specialisation, with it being afforded status as an autonomous branch and not part of the Torpedo Branch, as had previously been the case. By this time the early over-optimism about asdic’s potential had worn off, and the experts were becoming aware, through the medium of exercises, that a screen was far from certain to detect a submarine. Similarly, it was becoming clear that the range of the sensor would not allow profitable employment of hunting groups on the high seas. Because of the youth of the branch, however, there was still no expert representation at the Admiralty, and those torpedo officers who had some knowledge of modern A/S were still only to be found in the Tactical and Signal Divisions. The Plans Division, significantly, lacked any real understanding of the subject. As a result of this, there were sections of the Staff who retained some of the early optimism, and among them there were still influential officers who believed that it would be possible to use asdic to sweep the submarine menace from the seas. 177 Copyright © 2003 George Franklin


By 1931 tactics in defence of a fleet had been largely standardised, the officers’ branch had grown to a strength of 29, specialists were moving between submarine and surface ship appointments, and, although communications between aircraft and ships were still a problem, air A/S tactics were becoming standardised. The early 1930s saw a significant change in the direction of antisubmarine development. The Japanese submarine attack on the main fleet remained a serious menace, but a second threat was beginning to develop in Europe, and this was a very different one. The German navy, whose submarine arm had so nearly strangled Britain in 1917, was suspected of planning to rebuild that arm. Although certainly capable of building cruisers and heavier ships for commerce raiding, the Germans were not, in the short or medium term, going to be able to threaten a fleet action, as they had in the First World War, and as the Japanese could. Their submarines could, therefore, have only one use against Britain, namely another attack on maritime trade. The Royal Navy’s reaction to this threat was not as slow or as ineffective as has been made out. In 1932 the Controller stated that the navy would design asdic-fitted patrol and escort ships, building a small number of each so as to test the designs and be ready to build them in large numbers if war came. That same year sketch designs were ready, and the 1933 programme included the construction of one of each type. The first of these trade defence vessels were fitted with adapted destroyer asdics, but in 1934 the type 124, the first set specifically designed for escorts and patrol ships, was introduced. Even before the arrival of these ships in the fleets, ‘P’ boats and old destroyers were being employed at Portland to devise trade defence tactics. Notwithstanding the intention to build large numbers of escort ships during war, it was realised that sufficient numbers were not going to be available to provide convoys with the sort of screens enjoyed by battle fleets. Exercises were therefore carried out using small numbers of escorts, and the tactical experts concluded that a submarine was not likely to be detected before it had attacked. Convoys would therefore rely for their defence on the subsequent prosecution of the submarine that had revealed itself by attacking, and an attrition rate of one merchantman for one submarine was implicitly accepted. Another result of the limited numbers of escorts that would be available in the early months of war was the Admiralty’s interest in trawlers. Useless for ocean work, and unable to escort anything that went much faster than 9 knots, they would nonetheless be useful for local defence and some coastal convoy escort. A master list of trawlers suitable for requisitioning in war was thus drawn up, specifically built trawlers were supplied to Portland so that tactics could be trialled and personnel trained, and the type 123 trawler asdic was introduced in 1934. Most importantly, though, a specific reserve force of fishermen, trained in peace ready to man the trawlers in war, was built up. 178 Copyright © 2003 George Franklin

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Local defence of harbours and anchorages would also be provided by indicator loops, harbour defence asdic, booms and indicator nets, all of which were being developed and tested with a view to mass production in war. A better understanding of the behaviour of underwater sound and a growing experience in the use of asdic were beginning to indicate that surfaced submarines presented poor asdic targets. Well aware that a submarine was also hard to see at night, the Admiralty produced convoy instructions in 1934 in which it warned that submarines were expected to attack on the surface at night. Technology at the time allowed no response to this threat, and the solution seems to have lain in keeping very quiet about this vulnerability. Little progress was made in the mid-1930s in weapon development, the ahead thrown weapon having been abandoned, and depth charges remaining largely unchanged. Air weapon development was also progressing at a painfully slow pace, the emphasis still being on contactfused bombs rather than depth charges. Aircraft development was doing little better, and, although the Anson did enter service in 1934, Coastal Command’s status as the poorer cousin of what would become Bomber and Fighter Commands was looking unlikely to change. The 1935 Abyssinian crisis saw an acceleration in equipment purchases, which tested the theory that anti-submarine hardware could be built up in a hurry. Driven by the expectation of an imminent war, this led to the purchase of immediately useful, low-cost and relatively unsophisticated equipment such as depth charges, trawlers and harbour defence equipment. The contrast between long-term procurement issues, which tied in high-value and complex items with long lead times, and shortterm procurement of items that could be rapidly supplied is nicely demonstrated. When looking, therefore, at inter-war procurement of antisubmarine equipment, it is insufficient to pick up a contemporary copy of Jane’s Fighting Ships and count the escorts. What is important is to take into account whether tested designs, both of equipment and platforms, existed, and whether there was sufficient capacity to mass-produce the hardware in an emergency.3 This policy was quite clear throughout the 1930s, as the following two passages, one from an internal Admiralty memorandum and one from a CID paper, indicate: The full reserve of anti-submarine material to counter unrestricted submarine warfare is so large that it will probably never be provided in peace, and the production of the necessary number of sets and the training of personnel will, of necessity, take a long time after the outbreak of war. The necessity, however, for building up in peace as large as possible a reserve of material and trained personnel cannot be too strongly emphasised.4 179 Copyright © 2003 George Franklin


Naval plans, therefore, envisage building up in peace a skeleton organisation capable of rapid expansion on the outbreak of war… Naval plans are concerned chiefly with what minimum provision is necessary in peace to meet this form of [unrestricted] attack, which may start on or shortly after the war.5 Although short-lived, and not resulting in full mobilisation, the Abyssinian crisis indicated that the system, fundamentally, worked. The only other pre-war ‘live’ practice came when HMS Havock, patrolling off the Spanish coast during the Civil War, was fired on by an Italian submarine. She detected and hunted the boat for some hours, but no conclusive result was obtained. Subsequent intelligence indicated that the Italians had been severely shaken by the experience, and that a number of the depth charges had been dropped close to the boat. Much has been made of this episode, most commentators following Roskill’s line that ‘this comparative failure of the Asdic does not appear to have shaken British confidence in its effectiveness’.6 Hundreds, if not thousands, of exercise submarine prosecutions had taken place at Portland and in the fleets, the collective conclusion of which was that in around 50 per cent of hunts the submarine would be badly damaged or sunk. HMS Havock, whose asdic was not manned at the time of the attack because she was on passage, detected the submarine, attacked and, even though on her own, regained contact after the attack. Moreover, she managed this on an August afternoon in the Mediterranean, when the thermocline is at its most extreme and submarines even today are notoriously difficult to detect. The implicit suggestion of Roskill and his followers that this isolated action should have prompted the Admiralty to disregard exercise statistics and shift to some more effective policy seems, at best, to lack proportion. The systems and plans that were in place or under way in 1935 changed very little between then and the Munich crisis. The numbers of asdic destroyers in the fleets continued to grow, at the rate of around one flotilla per year, and the officer and rating specialists to man them were trained at Portland. Still, little happened in terms of weapon development and, owing to the failure of the RAF’s aircraft procurement programmes, the Anson remained the backbone of the land-based A/S air force. Asdic sets continued to improve, as did indicator loops. Paymaster Rear-Admiral Manisty built up the convoy infrastructure at home and abroad, a formal liaison with the merchant shipping industry was established through the Shipping Defence Advisory Committee, and a reserve of anti-submarine equipment was built up ready to be fitted to war-procured trawlers. The greatest shift in direction came with the realisation that the Kingfisher and Bittern class ships, satisfactory as they were for A/S duties, were too expensive and too technically advanced to be built in large numbers in war. The solution was the genuinely cheap and easy to build 180 Copyright © 2003 George Franklin

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Southern Pride whalecatcher. The first ship was ordered in March 1939, and went to sea early in 1940. When war came, it was discovered that U-boat attack on escorted convoys generally resulted at least in damage to the submarine, and the attrition rate of U-boats against escorted merchantmen was entirely unsustainable for the Germans. Independently sailed ships and unescorted convoys were expected to be vulnerable, but the scale of shipping loss among these classes was not foreseen, and the introduction of special slow convoys on the HX, HG and SC routes was an acknowledgement that the initial speed bracket of 9 to 15 knots for convoyed ships left too many slow ships sailing without protection. The feeling about vulnerability was summed up by the First Sea Lord when writing to one of his Commanders-in-Chief in the early days of the war: ‘I am surprised that we have not suffered more than we have because there really have been a large number of ships roaming about the ocean.’7 The main unexpected weakness, ironically, came in the one area for which the navy has been criticised for concentrating on, that is, warship defence. Here, as in convoy defence, it was found that the submarine was unlikely to be detected before making its first attack. Harbour defence was generally satisfactory, with the sinking of HMS Royal Oak being the only significant entry of a U-boat into a port or anchorage. Indeed, after a minesweeper had found and destroyed a Uboat in the Clyde, Dönitz decided that close-in attacks and mining operations should stop. This can only be to the credit of the boom defence vessels, trawlers, indicator loop stations and others who, from the first days of the war, defended the fleet and merchantmen at their most vulnerable, and have been celebrated neither in literature nor on film. Offensive patrols were thought by the experts to be ineffective, but actually proved more fruitful than had been anticipated, for the simple reason that more boats than had been expected revealed themselves either by attacking using gunfire or moving on the surface during daylight hours. The best an asdic patrol could do, however, was to wait in an area of likely U-boat activity to receive a sighting report. Attempts to use asdic to search expanses of water for dived submarines which may or may not have been there were both over-optimistic and misguided. This was not fully appreciated by some in the navy and many outside it. What Donald Macintyre describes as Churchill’s ‘considerable military knowledge and experience misapplied to naval matters’8 led the latter to declare: Nothing can be more important in the anti-submarine war than to try to obtain an independent flotilla which could work like a cavalry division on the approaches, without worrying about traffic or the U-boat sinkings, but could search large areas over a wide front. In this way those areas would become untenable to U-boats.9 181 Copyright © 2003 George Franklin


The employment of a carrier as part of such a patrolling group would allow a greater chance of detecting a boat on the surface, as would proper integration of shore-based aircraft patrols, and might have been a useful way to guide patrolling destroyers towards their targets, but such carriers were withdrawn as being too much at risk after the sinking of HMS Courageous. Captain John Mosse, an experienced inter-war anti-submarine officer, served in the war as anti-submarine and Senior Staff Officer to a striking group based on HMS Havelock. He sums up the problem faced by hunting groups in his memoirs: The convoys had their own close escorts, but we were to be an independent striking force, putting ourselves between the reported positions of U-boats and the convoys they were trying to intercept… For various reasons this policy was not very successful. The Atlantic is a big ocean and the range of Asdic was only about one mile.10 There was, however a well-thought-out argument for the use of offensive tactics, however ineffective they might be. A Plans Division paper written two months into the war noted that ‘This convoy system, augmented by other subsidiary measures, was sufficient to defeat the U-boat campaign in the last war, and has succeeded in inflicting considerable casualties on the U-boats in this war.’ A mining menace, however, was fast developing, and in order to prevent U-boats from laying minefields in UK waters it was necessary to divert resources away from convoy defence. To defend maritime trade, therefore, it was not sufficient merely to protect the merchant ships against direct attack, and the above-quoted paper concluded that ‘the U-boat will only be successfully mastered once and for all by defensive measures designed to destroy them regardless of the mission on which they are engaged’.11 It was found that when a submarine was detected in the vicinity of surface ships it was likely to be attacked with some success. Indeed one wartime review assessed that: ‘to sum up, the first six months of the war have shown that if the position of the U-boat is revealed close to A/S vessels the chances of destruction are high. The main problem is one of initial detection.’12 This reflected the position as anticipated by the anti-submarine organisation and as predicted by Portland exercises. Wartime conditions were, however, slightly different from those found at Portland for two reasons. First, the Portland analysis methods assumed that all depth charges were set to the correct depth, which was optimistic at a time when asdic gave no reliable indication of target depth. In the relatively shallow waters of the English Channel and the southern North Sea, a charge set to around 100 feet would detonate moderately close to the depth of the submarine, but in the western approaches and the Bay of Biscay the greater depth 182 Copyright © 2003 George Franklin

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increased the problem. Associated to this was the fact, apparently not properly considered at Portland, that the submarine could alter course to evade after the charges had been dropped. The Type VII U-boat, the main ocean-going class, had an operational depth of 100 metres, or 330 feet, and in the 33 seconds it took a depth charge to fall to that depth13 a submarine travelling at 6 knots could have moved 110 yards, making it virtually impossible to drop a charge within the 10-yard lethal range of the target, even if the depth had been correctly set. Acting against this disadvantage was the fact that asdic had been successfully shrouded in secrecy. The Germans had no idea at all how it worked, were unable to devise effective countermeasures and made easier targets than the RN submariners whose submarines had been used as practice targets at Portland. An RN submariner would try to keep end on to the transducer, so reducing the area against which the pulse could echo, and knew at what stage during an MRCS to increase speed and alter course. The German, meanwhile, would slow down, keep his rudder amidships and, if possible, lie silent on the bottom to reduce his own radiated noise, believing as he did that RN measures relied on passive detection. The fate of U-33 at the hands of HMS Gleaner illustrates the weakness of these tactics. These two factors, certainly in the early months of the war, effectively cancelled each other out with the result that the Portland hunt success matched wartime success with impressive accuracy. While the situation around a previously detected U-boat was as anticipated, the performance of screens against dived boats making their initial approach fell well below that which had been hoped for. The wartime report quoted above also stated that ‘in first considering the Asdic…it can be said that it has provided results approximating to those expected’ but of the specific problem of false contacts it conceded that ‘although this was fully realised in peace, it required the war to bring this out in relief ’.14 The CB 3002 reports included figures for ‘flotilla operating hours per false report’, which usually hovered at around one or two hours per report. This can be more usefully expressed as between 0.5 and 1 false reports per hour. Given that a flotilla was held to comprise six ships, this implies that each ship would gain asdic contact on something which turned out not to be a submarine two to four times a day. Wartime logs, whose narratives reported ‘Investigating Asdic contact…contact assessed non sub’ on at least a daily basis, indicate that the predicted false report rate was approximately correct. The Portland assessment of the operational impact of these false reports, however, may have been less satisfactory. In a four-hour exercise, during the course of which one expects to be attacked, each contact will be thoroughly and tenaciously investigated, the main body will be moved to 183 Copyright © 2003 George Franklin


avoid it and it will be treated as a submarine until definite evidence emerges that it is a rock, a shoal of fish etc. Faced with this level of vigorous prosecution, submarines are unlikely to be able to penetrate a screen. On the other hand, during the third week of a period of escort duty, when false contacts have been appearing on at least a daily basis and there has been no attack or other definite sign of a submarine, minds are likely to become less focused on each contact, notwithstanding the danger presented by wartime conditions. Under these circumstances it is hardly surprising that U-boats, despite appearing on asdic, were sometimes dismissed as false contacts and allowed to penetrate screens. Further, the Commander-in-Chief Mediterranean, writing in 1939, voiced concern about the accuracy of exercise results: It is considered that a great deal of the statistics…are the results of ‘short time’ exercises and are liable to create an optimistic impression of the A/S efficiency which may be expected in war. A commanding officer, knowing that his A/S efficiency is assessed on the results of tactical exercises, is tempted to use his best ‘team’ and, in nearly all cases, the A/S control officer is in charge throughout.15 This seems an entirely likely and understandable conclusion, and would indicate further why the German submariners, lacking any useful antiasdic tactics, fared little worse than those British boats against which peacetime exercises had been conducted. The broad and important conclusion of the above is that Roskill’s second contention, subsequently adopted by the vast majority of writers, that the RN overestimated the effectiveness of asdic is, in all areas other than that of false contacts, largely untrue. The view among anti-submarine experts was that asdic was useful for short-range hunting and prosecution of submarine contacts, but could not be profitably used for general searches. Wartime experience proved this to be the case. The only people, therefore, who overestimated asdic’s capabilities were those who had neither studied the subject nor consulted the experts. It was these people who, having spent the inter-war years blind to the progress which was taking place in antisubmarine warfare, adopted the misguided and costly strategy which favoured inefficient offensive hunting groups at the expense of defensive but effective convoy escort. NOTES 1 Stephen Roskill, Naval Policy Between the Wars, 2 vols, Collins, London, 1968 and 1976, Vol. 1, p. 346, citing ADM 1/8609, Minute dated 27 July 1921. 2 Ibid., Minute dated 30 July 1920. 3 Andrew Gordon, British Seapower and Procurement Between the Wars: A Reappraisal of Rearmament, Naval Institute Press, Annapolis, MD, 1988, contains an exten-sive


THE SYSTEM

4 5 6 7 8 9 10 11 12

13

14 15

discussion of the largely successful attempts of the Admiralty to develop reserve capacity which would allow wartime production of such short lead time items as munitions, aircraft and small ships. NMM CHT 1/3, Memo probably written by Capt. Grace, Capt. A/S, in 1932, entitled ‘Anti-Submarine Measures’. PRO CAB 4/26, CID 1318-B, Defence Against Submarine Attack, March 1937, p. 4. Roskill, Naval Policy, Vol. 2, p. 383. Pound to Forbes, 15 Sept. 1939, in CHURCH ROSK 4/19. Donald Macintyre, The Battle of the Atlantic, B.T.Batsford, London, 1961, p. 29. Churchill as First Lord to Pound as First Sea Lord, 20 Nov. 1939, in CHURCH ROSK 4/15. IWM 90/23/1, Memoirs of Captain John Mosse. PRO ADM 1/10084, A/S Policy, 1939, Paper by D of P dated 26 Nov. 1939. IWM, Papers of Vice-Admiral Sir Peter Cazalet, undated paper believed to have been written in 1940, ‘Brief Review of Anti-Submarine Operations in the First Six Months of the War’. Pre-war depth charges fell at 10 feet per second. The modified Mark 7, which fell at the faster rate of 16.5 feet per second, was not introduced until well into the war. See Willem Hackmann, Seek and Strike: Sonar and the Royal Navy 1914–1954, John Murray, London, 1995, p. 304. IWM, Papers of Vice-Admiral Sir Peter Cazalet, ‘Review of Anti-Submarine Operations’. PRO ADM 1/9942, A/S Exercises, C in C Med Half Yearly Report on A/S Operating, 26 May 1939.


Conclusion

In the Introduction it was stated that the book would attempt to answer five key questions, and as a conclusion these will now be addressed in turn. 1. Did the anti-submarine organisation of the Royal Navy make thorough studies of the likely tactics and strategy of the anticipated enemy, and were the results of these studies realistic?

The RN practised anti-submarine defence of warships, troopships and convoys. All three would undoubtedly be attacked by any one of the three rising enemies of the period. Further, as the German threat emerged, it was correctly judged that the future war would involve an unrestricted submarine attack on trade, so overall one can conclude that the appreciations of the enemy’s likely strategic stance were correct. There does not, however, appear to have been any real effort to study German, Japanese or Italian submarine tactics. No clear idea developed about whether boats would attack singly or in groups, whether attacks would be conducted at long range or from inside the convoy, or whether there would be an effort to pick off the escorts before moving in to attack the convoy. Rather than rely on intelligence assessments of likely enemy actions, it was left to the RN’s submariners to work out how they would go about attacking the various targets, and the tactics thus developed were then countered by the anti-submarine community. The criticism has been levelled that this method led to an assumption that German submariners, like their British counterparts, would be more inclined to attack heavy warships than merchant vessels. The fact is that, while the majority of German submarines were indeed tasked to attack merchant traffic, no opportunity to mount an ambush or an attack on warships was missed, and the public lionising of the COs who sank the Royal Oak and the Courageous leaves one in no doubt that they were considered valuable targets. Study of attack tactics would have been impossible before the Germans started to redevelop their U-boat arm in 1935, and might anyway have led to misapprehensions as to what the German submariners would actually do in an attack. Dönitz insisted in training that U-boats should


CONCLUSION

press in to attack from very close range, but in war the range of the attack depended vastly on the experience, skill and determination of the CO and crew of the attacking boat. A uniform assumption, therefore, that all boats would attack in accordance with the Dönitz doctrine might have led to mistaken counter measures. The specific and widespread accusation that the Royal Navy failed to anticipate the danger of surfaced night attack has been shown to be untrue. Small surface ships and surfaced submarines were known to make bad asdic targets, it was widely acknowledged that a surfaced submarine was hard to see by night, and convoy instructions warned of the danger of surfaced night attack. The navy was, however, unprepared to counter this attack because the available technology allowed no means of detecting a surfaced boat by night. The only real shortcoming of practising against the RN’s own tactics was that it presupposed an enemy understanding of the still very secret asdic. In the event, the Germans clearly did not understand how asdic worked, and devised inappropriate countermeasures, which made the British anti-submarine methods more successful than peacetime exercises might have suggested. 2. Did the exercises and trials carried out test the conditions anticipated, and did they prepare personnel for the anticipated war?

The Portland hunting and searching exercises almost all started with the submarine in a known position anything between 2 and 20 miles from the escorts which were to hunt it. In some cases the submarine started off dived, and in some it dived when seen from the destroyers. This is exactly what happened in war, escorts and patrolling ships going to the position of a submarine that had made an attack or been detected by aircraft, and it is unsurprising in these conditions that such a high proportion of the submarines so hunted were destroyed or badly damaged. The hunting exercises fell down, however, in the single but important fact that the potentially variable depth of the submarine was not taken into account when assessing the success of depth charge attacks. Exercises in attacks on formations of ships were generally conducted in a manner consistent with the subsequent war experience, with the exception of the inevitable compromises for peacetime safety. Ships at night, for instance, operated with their lights on, and submarines tended to be kept on the surface when they might otherwise have dived to avoid detection or attack. There were few exercises in patrol tactics, the only recorded one being that in which the relative values of patrol and escort were investigated.1 The only part of a patrol, however, which merited much practice was the search for a localised submarine and its subsequent prosecution, and this was well practised in the hunting exercises. 187 Copyright © 2003 George Franklin


Exercises in the employment of aircraft to search were frequent and realistic, though geography dictated that there was an unsatisfactory degree of liaison between RAF aircrew and ships’ officers after combined exercises. Exercises were carried out both with and without air support, so the mid-Atlantic action away from shore-based air support was allowed for, if only by default. The only real failing of exercises in air operations was the practice of declaring carriers to be ‘out of the exercise’ and thus unsinkable, for safety reasons, when launching or recovering aircraft. This meant that carriers got into the habit of moving out of formation and away from escorts with impunity, which would make them unnecessarily vulnerable in war. 3. Were the wider navy, the relevant sections of the air force, and policy makers outside the services kept aware of progress in, and limitations of, anti-submarine capability?

There is no doubt that the community of anti-submarine specialists, and some other involved officers, were aware of the limitations of the equipment. There is also little doubt that there were large numbers of influential officers who did not appreciate what asdic could and could not do. The first reasons for this would appear to lie in the organisational make-up of the Naval Staff, and the tribal branch structure of the Royal Navy. To take the first point, it has already been given that the anti-submarine expertise of the Naval Staff was limited to a core of officers who would frequently return to the same area, concerned primarily with procurement and tactical development, and that there were few if any in the Operations and Planning Divisions who had understanding of or experience in antisubmarine matters. From this comes the natural conclusion that those who conducted the strategic planning did so without the benefit of an appreciation of asdic’s capabilities and limitations. Further, the normally constructive tension between branches seems to have broken down, with the new A/S branch and the established gunnery branch having a common interest in talking up the A/S capability. 4. Were the procedures developed by the anti-submarine specialists understood by, and integrated into the operating procedures of, the wider navy?

As has been shown, there were a number of anti-submarine specialists serving with the fleets. They were to be found in flagships, destroyer and submarine squadron commands and ships within those squadrons, all had regular contact with Portland and they were employed to disseminate the latest tactical procedures and conduct training of ships’ teams. Any seagoing officer who had a need to ask questions about procedures or tactics had access to a trained expert, and procedures do seem to have 188 Copyright © 2003 George Franklin

CONCLUSION

been well disseminated. Anti-submarine tactics were generally well understood in the fleets, reactions to an attack took place with the minimum of fuss and signalling, standard screens were well known and understood, and those commanders who took the trouble to consult their experts very rarely found themselves at a loss. On a tactical level, then, the system and the individuals do seem to have served the navy well. At the strategic and operational levels, though, as has already been discussed, things were clearly less well arranged 5. Did the conditions anticipated actually materialise?

The expectation was that unrestricted submarine attack on trade would start early, if not immediately, on the outbreak of war with Germany. That, broadly, is what happened. Attempts to attack heavy fleet units and, where available, troopships were anticipated and did occur. In the wake of the Anglo-German naval agreement in 1935 a number of appreciations were made of the German ability to build submarines, and it was concluded that by the end of 1939 they would be able to operate between 56 and 66 U-boats. In the event, Dönitz had 56 boats available in September 1939, so the level of attack was, initially, as predicted. Given the strategic assumption that France would not fall, the RN anticipated that the majority of submarine attacks would take place around Britain’s coasts and in the eastern Atlantic approaches to the UK, and again this was the case until the basing of U-boats in the French Biscay ports radically changed the geography of the attack on trade. In practical terms, the manuals published between the wars, even in the late 1930s, indicated that ships escorting a convoy could not reliably expect to detect a submarine before it attacked, but that once it had revealed its position asdic would allow the escort a good chance of prosecuting it. This, broadly, proved to be the case in war; there is no recorded instance of any asdic-fitted ship stumbling unexpectedly across a dived submarine, but those submarines which had revealed their approximate positions generally suffered at least some sort of asdic-directed attack. It was anticipated that submarine attack on convoys would not be profitable, and as has been shown the attrition rate of those boats that did attack escorted convoys was entirely unacceptable for the German navy. There was, however, a larger than expected number of independently sailed merchant ships, and these suffered badly. Further, A/S ships that should rightly have been dedicated to escort duties were, through misguided operational command decisions, committed to unprofitable offensive action. The resulting unescorted convoys suffered without being able to hit back.



It was expected that the large numbers of escorts that were provided for fleet units and troopships would make submarine attack virtually suicidal. It is an inescapable fact that the speed available to warships and troopships made them harder targets for sub mariners. The expectation, however, that with a large number of escorts one could build a wall of steel ahead of such a force proved to be misguided. The actual experience was that, much as with convoy defence, it was only the submarine which initially revealed an approximate position that would be detected and attacked. Although the many ships of a battle squadron screen would make the initial search and detection of the localised submarine easier, the doctrine was for only two ships to conduct the attack. The heavy warship with a squadron of destroyers in a screen was thus actually little better off than the convoy with an escort of two. Overall, then, A/S development was initially driven by a general awareness of the potential threat posed by submarines. The growth of the Japanese menace directed this effort towards the defence of warships, and in the late 1930s the reconstruction of the German U-boat arm dictated an increased emphasis on trade defence. Thus motivated, the Admiralty established officers’ and ratings’ A/S branches while achieving substantial advances in tactics and equipment. In the early months of the war German U-boats found that it was hazardous and generally unprofitable to operate in the vicinity of British A/S forces. The strategic misdirection of these tactically efficient forces, however, meant that U-boats were still able to find large numbers of unprotected targets. The fundamental British weakness came not from a failure to develop A/S methods and equipment, but from a widespread misunderstanding of what had and had not been achieved. The mistaken belief held in certain quarters that asdic enabled a dived submarine to be hunted like a surface ship led to an overreliance on patrol as a tactic. When, as the experts had predicted, patrol proved ineffective, there was a tendency in the wider navy to overcorrect, concluding that asdic was largely useless and, by extension, that it had not been properly developed in the interwar years. It is my hope that this book has demonstrated these conclusions, widely accepted for nearly 50 years, to be unfair to both Portland and the Tactical Division. NOTE 1 Exercise TP1, March 1935.


Appendix A

Theory of Asdic

As this study makes constant reference to asdic, this appendix seeks to set out the basics of how asdic worked, and to explain the state of understanding of the behaviour of underwater sound as it stood at the outbreak of the Second World War. The Admiralty Research Laboratory at Teddington conducted a great deal of pioneering work in this area during the inter-war years, and it should be noted that in 1919 very little was understood about the subject. It was suspected that sound refracted as it passed through water, but there was no understanding of how it refracted, or of the factors that caused variations in sound velocity; indeed it was proving very difficult to determine the speed of sound in water. It was evident that sound attenuated with distance, but no proper explanations had been found as to how, and the noise generated by water as it flowed round objects such as ships’ hulls had never been properly studied. BASIC PRINCIPLES It is generally understood that radar works by reflecting electromagnetic pulses off objects to obtain their bearing and, by measuring the time taken for the echo to return, their range. Asdic, or sonar as it is now known, works on the same principle, but uses sound instead of electromagnetic energy, and is only really effective underwater. The key part of the asdic apparatus is the transducer, which can be thought of as a form of searchlight. The operator would point the transducer in a certain direction and, by applying an electric current to the quartz crystals in the transducer’s face, could cause it to send out a pulse of sound in the form of a beam. When the pulse had been sent, the transducer would sit silent for a while, waiting for any echoes to return to it. Any sound that did rebound off an object in the water, and return to the transducer, would agitate the crystals, causing then to generate a small electric current in the receiving circuitry, which would indicate to the



operator that he had detected something. The direction in which the transducer was pointing would show the approximate bearing of the object, and the time between transmission and reception would give a range. In inter-war sets, the current induced in the receiving circuitry would generally be converted into a sound signal for the operator’s headphones, or later for a loudspeaker. Detection at range could be a particular problem as the sound attenuated with range and, although in a directed beam, spread on both the outward and return legs so that only a small proportion of the echo would actually hit the transducer. FALSE CONTACTS As sound reflects off submarines so it also reflects off other local discontinuities in the water mass, such as whales, shoals of fish, rocks which protrude from the seabed, bubbles and disturbed sections of water which have been subject to local mixing, for instance from a ship’s hull or propellers. To an experienced asdic operator some of these would appear to be obvious ‘non-sub’ contacts, and analysis of the contact’s movement, size and echo strength would all help this process. Much time would, however, be spent investigating contacts that were not submarines. Inevitably, this also led to submarines being wrongly classified as non-sub and thus being able to escape. An ongoing hunt would present particular false contact problems as the wakes of ships might show up on an asdic set, as might the very disturbed and aerated water after a depth charge attack. The asdic operators during a hunt would thus have to be particularly vigilant to ensure correct classification. OTHER INTERFERENCE There were other factors that could reduce asdic’s effectiveness. The first came from reverberation of the sound of the many small objects that exist in the sea. These objects, such as small fish, water bubbles, pieces of sediment etc., might not be distinct enough to give a false echo, but would give a continuous low-level echo that could easily disguise a real submarine. The best parallel for this is a car’s headlights in fog, which give lots of small returns that, while not mistaken for an object to be avoided, may mask such a object. A second factor was the ambient noise of the ocean. This can come from fish, waves, shipping, deep volcanic activity or any number of other causes. Inter-war asdic sets generally worked at a frequency of around 192 Copyright © 2003 George Franklin

APPENDIX A

10–25 kHz, and, although the levels of ambient noise at these frequencies is not high, there could still be enough to mask a returning echo. The final factor, and possibly the most limiting, was the ship’s own noise, whether from machinery, the flow of water around the hull and the asdic dome, or other causes. This, like the ambient noise, would be heard in the operator’s headphones, and could easily mask a returning echo. Ship’s self-noise increases rapidly with speed, and this is why asdic works very much better at slow speeds, and the sensor becomes virtually useless beyond a certain limiting speed. For the early arrangements this limiting speed was as low as 13 knots, but with later sets it went up to as high as 20 knots. In any event, though, the slower the ship’s speed the more likely was the detection of the submarine. PROPAGATION OF SOUND UNDERWATER In a homogeneous body of water sound travels, over the distances with which asdic theory is concerned, in straight lines. In a body of water whose properties differ with depth or horizontal displacement, however, sound will be refracted or reflected. Appreciable horizontal differences only tend to occur at ocean fronts, and are sufficiently rare and complex to be disregarded for our purposes, so we will concentrate on the differing properties of the ocean as one goes deeper. As light refracts when passing from air to the glass of a prism, so sound in water refracts as it passes between parts of water with different properties. The refraction is caused by differences in the velocity of sound, which in turn are caused by differences in pressure, temperature and salinity. The key point, which should be remembered, is that sound will be refracted towards a region of lower velocity. Thus, in the body of water shown in Figure 13a, in which the velocity reduces with depth, known as a negative gradient, the sound produced by the asdic set will be refracted down, as shown, and a submarine in the shaded area may operate with relative impunity, as the asdic pulses will never reach it. Similarly, in the positive gradient shown in Figure 13b the pulses will be refracted upwards. In this case it is clearly the deep boat that poses the problem. Both of the above cases have assumed a water mass of gradually changing velocity. Where a sharp change occurs some of the sound will be reflected off the boundary, as some of the light shone at a prism will reflect off the surface glass, never to enter the prism. If therefore, as in the purely theoretical Figure 13c, there is a sharp boundary at a given depth, some of the sound will be reflected from that boundary. It should be noted that the air-water interface, known to the uninitiated as the surface of the sea, represents just such a distinct velocity shift.



Figure 13: Subaqueous Sound Paths

THE PROPERTIES OF THE WATER COLUMN The negative velocity profile shown at Figure 13a is, in simplification and to the depths to which a German U-boat could dive, the general rule in the North Atlantic and the North Sea other than in summer. There are, however, two circumstances that may modify this pattern. The first is most commonly found in the summer, becomes extreme in tropical waters, and is often known as the afternoon effect. The sun, as a warm day progresses, heats up the surface of the water, so producing an exaggerated negative gradient as shown in Figure 13d. In these circumstances the shaded blind area increases and the submarine is even less likely to be detected. The second common modifier is caused by surface agitation, usually from waves, mixing the top few metres of water so that there is no discernible difference in temperature from the surface down to, say, a depth of 10 metres. In this circumstance the effects of pressure unmodified by temperature will give the profile shown in Figure 13e, thus providing what is known as a surface duct. This condition, caused by anything more than a slight sea, and most pronounced where there is no great heating influence on the surface, is not uncommon in the North Atlantic.


APPENDIX A

DETECTION OF THE SURFACED U-BOAT The first point which should be noted about the problem presented by a surfaced U-boat is that the amount of the boat which is under water, and which will thus reflect sound, is less than in the case of a fully submerged boat. The second point is that in conditions of negative temperature gradient (Figure 13a) and especially the exaggerated negative gradient provided by the afternoon effect (Figure 13d) the surfaced boat will be able to operate down to relatively short ranges without serious danger of detection. The third point, and this should be borne in mind by those who describe the surfaced boat as undetectable by asdic, is that a body at or near the surface may give a good return in conditions of surface mixing (shown in Figure 13e). Indeed, it is the author’s experience that in these conditions even small surface vessels, down to fishing vessels of comparable displacement to a surfaced U-boat, give very definite returns. A surfaced submarine, therefore, presents a less satisfactory asdic target, but is far from being undetectable.


Appendix B

Portland Exercise Success Criteria

ATTACKS Successful Attack—An attack in which one depth charge of a pattern of five would have landed within 10 yards of the hull of the submarine. Partially Successful Attack—An attack in which one depth charge of the pattern would have landed within 20 yards of the hull of the submarine. Unsuccessful Attack—An attack in which no depth charge would have landed within 20 yards of the submarine. Doubtful Attack—An attack in which there is insufficient data for analysis. HUNTS Successful Hunt—A hunt in which one or more successful attacks are carried out, or a hunt in which two or more partially successful attacks are carried out and in which one or more A/S vessels are in contact with the submarine at the end of the hunt. Possibly Successful Hunt—A hunt in which a partially successful attack is carried out, but which does not otherwise comply with the requirements of a successful hunt. Indecisive Hunt—A hunt in which no successful or partially successful attacks are carried out, but in which one or more A/S vessels are in contact at the end of the hunt. Unsuccessful Hunt—A hunt in which no successful or partially successful attacks are carried out and in which no A/S vessel is in contact at the end.1 These criteria took account only of the plan position of the submarine at the time of launch of the depth charges, and no allowance was made for its depth.


APPENDIX B

In 1931 the criteria for attack success were changed so as better to reflect the doctrine surrounding depth charge tactics. A deliberate attack would be considered successful if any part of the submarine was within 50 yards of the centre of the pattern, and unsuccessful if not, there being no criteria for ‘partial success’. The criteria for a decisive counter-attack are the same as for a successful deliberate attack. A harassing counterattack was one in which the submarine was between 50 and 100 yards away from the centre charge, and anything which missed by more than 100 yards was considered to be fruitless.The document which promulgated these changes in criteria conceded, once again, that attacks are only analysed and classified according to their position in the horizontal plane. The factor of depth, both of Submarine and setting of depth charge must be borne in mind when drawing any conclusions concerning the question of attacks as a whole.2 The same document redefined the criteria for hunt success such that a successful hunt was either one in which three or more successful attacks were made, in which case there was no requirement for any ships to be in contact at the conclusion, or one in which two successful attacks had been made and one vessel was still in contact at the end of the hunt. The criteria for hunt success were thus made more stringent. NOTES 1 PRO ADM 186/457, CB 3002/26, p. 49. 2 PRO ADM 186/140, CB 1868/1931, Anti-Submarine Practice Memoranda.


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PRIMARY SOURCES Public Record Office Series of Particular Use: ADM 1 ADM 116 ADM 167 ADM 186 ADM 204 ADM 218 AIR 2 AIR 14 AIR 15 CAB 2 CAB 4 CAB 53

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Mr A.Lang Brown Admiral Sir Roderick MacDonald Admiral Sir Ian McGeoch Captain J.Mosse Vice-Admiral A.G.Talbot Naval Museum, Portsmouth Personal Papers of: Midshipman R.Beckwith Lieutenant-Commander A.Layard Midshipman R.Michell Midshipman W.Parker Churchill College, Cambridge Personal Papers of: Sir Winston Churchill Commander Fawcett Admiral Sir Dudley Pound Captain S.W.Roskill Interviews and Correspondence With: Captain R.de L.Brooke Captain Brooke was a pre-war destroyer officer and wartime destroyer commanding officer with wide exper ience of anti-submarine operations, including the successful sinking of an Italian submarine in the Mediterranean. Captain Barrie Kent Captain Kent was a career communications specialist who in retirement wrote a history of the communications branch of the Royal Navy. Vice-Admiral Sir Ian McGeoch Admiral McGeoch was a pre-war submariner and wartime submarine commanding officer with wide experience of anti-submarine exercises and operations, including having his submarine sunk by an enemy destroyer in the Mediterranean. Admiral Sir Anthony Morton Admiral Morton was a wartime destroyer officer with considerable experience in anti-submarine work who has subsequently made a private academic study of the subject. 199 Copyright © 2003 George Franklin


Lieutenant-Commander D.Waters Lieutenant-Commander Waters was a pre-war and wartime Swordfish pilot who went on to co-author the Naval Staff history of the Second World War trade defence campaign. SECONDARY SOURCES Articles Arnould-Foster, D., ‘Our Anti-Submarine Requirements of the Future’, Royal United Services Institute Journal, LXXIV (Aug. 1929). Clarke, A.W., ‘Air Cooperation with the Fleet’, Royal United Services Institute Journal, LXXIII (Aug. 1928). Dennistoun-Burney, C., ‘The Influence of Aircraft on Sea Power’, Royal United Services Institute Journal, LXXV (Aug. 1930). Franklin, G.D., ‘A Breakdown in Communication: Britain’s Over-estimation of Asdic’s Capabilities in the 1930s’, Mariner’s Mirror, 84, 2 (May 1998), pp. 204– 14. Robertson, E.D.M., ‘The Value of Aircraft for Protecting Seaborne Trade’, Royal United Services Institute Journal, LXXVIII (Aug. 1933). ‘Securus’, ‘Air Defence of our Sea Communications’, Royal United Services Institute Journal, LXXXI (Aug. 1936). Waters, D.W., ‘Some Reflections upon the Battle of the Atlantic, 1939–1945, and Historic Maritime Operational Research’, Naval Review, 83, 4 (Oct. 1995) to 84, 2 (April 1996).

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BIBLIOGRAPHY Buckley, John, Constant Endeavour: The RAF and Trade Defence 1919–1945, Keele University Press, Keele, 1995. Buxton, Ian, ‘British Warship Building and Repair’, in Stephen Howarth and Derek Law (eds), The Battle of the Atlantic: The Fiftieth Anniversary International Naval Conference, Greenhill Books, London, 1994. Campbell, John, Naval Weapons of WWII, Conway Maritime Press, London, 1985. Chatfield, Lord, The Navy and Defence, Heinemann, London, 1942. Chatfield, Lord, It Might Happen Again, Heinemann, 1947. Churchill, Winston S., The Second World War, Vol. 1, The Gathering Storm, Cassell, London, 1948. Cunningham Papers, The, Vol. 1, 1939–1942, Navy Records Society, Aldershot, 1999. Defeat of the Enemy Attack on Shipping, 1939–1945, The, originally CB 3304 (1A), Navy Records Society, Aldershot, 1997. Dönitz, Admiral Karl, Die U-bootwaffe, E.S.Mittler, Berlin, 1939. Dönitz, Karl, Ten Years and Twenty Days, Weidenfeld & Nicolson, London, 1959. Doughty, Martin, Merchant Shipping and War: A Study in Defence Planning in the Twentieth Century, Royal Historical Society, London, 1982. Eden, Sir Anthony, Facing the Dictators, Cassell, London, 1962. Edwards, Kenneth, The Navy of Today, Blackie, Glasgow, 1939. Elliot, Peter, Allied Escort Ships of World War II, Macdonald & James, London, 1977. Ferris, J.R., The Evolution of British Strategic Policy 1919–1926, Macmillan and King’s College, London, 1989. Glover, William, ‘Manning and Training the Allied Navies’, in Stephen Howarth and Derek Law (eds), The Battle of the Atlantic: The Fiftieth Anniversary International Naval Conference, Greenhill Books, London, 1994. Gordon, G.A.H., British Seapower and Procurement Between the Wars: A Reappraisal of Rearmament, Naval Institute Press, Annapolis, MD, 1988. Hackmann, Willem, Seek and Strike: Sonar and the Royal Navy 1914–1954, John Murray, London, 1995. Haggie, P., Britannia at Bay: The Defence of the British Empire Against Japan, 1931– 1941, Clarendon, Oxford, 1981. Hague, Arnold, Sloops, 1926–1946, World Ship Society, Kendal, 1993. Hague, Arnold, The Allied Convoy System 1939–1945: Its Organisation, Defence and Operation, Chatham, London, 2000. Harris, Arthur, Bomber Offensive, Collins, London, 1947. Hezlet, Arthur, The Submarine and Sea Power, Peter Davies, London, 1967. Hezlet, Arthur, The Electron and Sea Power, Peter Davies, London, 1975. Howarth, Stephen, and Law, Derek (eds), The Battle of the Atlantic 1939–1945: The Fiftieth Anniversary International Naval Conference, Greenhill Books, London, 1994. Hoyt, Edwin P., The U-Boat Wars, Robert Hale, London, 1985. Hyde, H.M., British Air Policy Between the Wars, 1919–1939, Heinemann, London, 1976. 201 Copyright © 2003 George Franklin

BRITAIN’S ANTI-SUBMARINE CAPABILITY, 1919–1939 Ismay, The Memoirs of General the Lord Ismay, Lon, London, 1960. Joubert de la Ferté, Philip, The Fated Sky, Hutchinson, London, 1952. Joubert de la Ferté, Philip, The Third Service, Thames & Hudson, London, 1955. Kingsley, F.E. (ed.), The Development of Radar Equipments for the Royal Navy 1935–45, Naval Radar Trust, Macmillan, London, 1995. Lenton, H.T., British Fleet and Escort Destroyers, Macdonald, London, 1970. Lenton, H.T., British and Empire Warships of the Second World War, Greenhill, London, 1998. MacBean, Wing-Commander John A., and Hogben, Major Arthur S., Bombs Gone: The Development of British Air-dropped Weapons from 1912 to the Present Day, Patrick Stephens, Wellingborough, 1990. Macintyre, Donald, The Battle of the Atlantic, B.T.Batsford, London, 1961. Maiolo, Joseph A., The Royal Navy and Nazi Germany, 1933–39: A Study in Appeasement and the Origins of the Second World War, Macmillan, in association with King’s College, London, 1998. Mallett, Robert, The Italian Navy and Fascist Expansionism, 1935–1940, Frank Cass, London, 1998. Mallmann Showell, Jak P., The German Navy in WWII, Arms & Armour Press, London, 1979. Marder, Arthur, Old Friends, New Enemies: The Royal Navy and the Imperial Japanese Navy, Strategic Illusions 1936–1941, Clarendon Press, Oxford, 1981. Padfield, Peter, Dönitz, the Last Führer, Granada Publishing, London, 1985. Padfield, Peter, War Beneath the Sea: Submarine Conflict 1939–1945, John Murray, London, 1995. Pratt, Lawrence C., East of Malta, West of Suez: Britain’s Mediterranean Crisis 1936– 1939, Cambridge University Press, Cambridge, 1975. Preston, Antony, V & W Class Destroyers 1917–1945, Macdonald, London, 1971. Price, Alfred, Aircraft versus Submarine: The Evolution of the Anti-Submarine Aircraft 1912–1972, Kimber, London, 1973. Prien, Günther, I Sank the Royal Oak, Grays Inn Press, London, 1954 (originally published in German, 1940). Ranft, Bryan (ed.), Technical Change and British Naval Policy 1860–1939, Hodder & Stoughton, London, 1977. Rayner, D.A., Escort, William Kimber, London, 1955. Robertson, Terrence, Walker RN, Evans Bros, London, 1956. Rohwer, Jürgen, Axis Submarine Successes of World War Two: German, Italian and Japanese Submarine Successes, 1939–1945, Greenhill, London, 1999. Roskill, Stephen Wentworth, The War at Sea, 3 vols, HMSO, London, 1956. Roskill, Stephen Wentworth, Naval Policy between the Wars, 2 vols, Collins, London, 1968 and 1976. Scalia, Joseph M., Germany’s Last Mission to Japan: The Sinister Voyage of U-234, Chatham, London, 2000. Sharpe, Peter, U-boat Fact File 1935–1945, Midland Publishing, Leicester, 1998.


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