27 October 2000
Source: Allied and Axis Signals Intelligence in World War II, edited
by David Alvarez; Frank Cass, London, Portland, OR. First published 1999
in Great Britain. ISBN 0 7146 4958 9 (cloth) ISBN 0 7146 8019 2
(paper). Abstracts of articles below.
DAVID KAHN
The historiography of cryptology has come a long way. At first it depended almost exclusively upon the classics. All early books cited Herodotus, Plutarch, Suetonius. As the early works -- Porta, Vigenere, Selenus -- themselves aged into the classics of the field, they were cited in their turn. But no one probed the archives. In part historians had not yet adopted Leopold von Ranke's procedure of studying the documents of the time to discover wie es eigentlich gewesen ist -- how it really was. And in part there was little to probe. Before the telegraph, signal communication was limited to horseback rides and wagging flags and bonfires; cryptography rarely served and cryptanalysis came into play only infrequently. These rare uses left few documentary traces and seldom affected the world. Moreover, the basic cryptosystem of the time was the intellectually uninteresting nomenclator. How different things are today!
Since the advent of the telegraph and the radio, the volume of cryptologic documents has become overwhelming. During World War II, millions of secret messages were transmitted in original and challenging cryptosystems. Hundreds of thousands of these messages were solved by the enemy. The volume is often literally too great for a single researcher to digest. And cryptanalysis had great effects on events. In fact, many of these effects, such as the role of the breaking of Enigma in defeating the U-boats and the solution of Japanese codes in winning the Battle of Midway, were so important, so well known that, unlike many of the recondite events studied by historians, they are known even to advanced-placement high school students. And these documents enjoy an intrinsic interest of their own: they were once among the most precious, the most tightly held secrets of a nation.
Bradley Smith's contribution indicates some of the mouth-watering documents that await seasoned scholars and doctoral candidates alike in Britain's Public Record Office. As this collection shows, cryptologic research has expanded from the customary study of how secret intelligence clandestinely controlled the political and military actions of armies and states toward their enemies to an examination of how they dealt with their friends. Brad Smith's original books in this regard are followed here by the useful studies of Lee Gladwin, though his does not deal with the realpolitik of America's and Britain's solving one another's codes, and David Alvarez, which touches upon the cryptologic mutuality of allied nations. Both once again demonstrate Lord Palmerston's axiom of 1848 that countries have no eternal allies and no perpetual friends, only eternal and perpetual interests.
More, cryptologic research is no longer restricted to Western European studies, as it long has been, but, with Maochun Yu's pathbreaking study of Chinese cryptology, advances to Asia. Rebecca Ratcliff discusses a problem rarely treated in cryptologic history, one that in this case is of great interest to students of the solution of the Enigma: what do codemakers do when they suspect their codes are compromised? Martin Thomas explores a matter all but undiscussed in cryptologic history, namely, Vichy France's cryptology, about which this writer has been curious since, some 30 years ago, Charles Eyraud told him that he had worked in its codebreaking bureau. The other essays throw needed light on other, better known problems of Sigint history.
All in all, this fine collection advances cryptologic historiography in many ways, and workers in the field are grateful to David Alvarez, its editor, and to the authors for their excellent and useful work.
Great Neck, New York
April 1999
[pp. 168-175.]
BRADLEY F. SMITH
Britain and the United States have a long and creditable history regarding the opening of their records on foreign relations. During the French revolutionary wars, and on into the mid-nineteenth century, the British and American governments frequently released statements and documents setting forth their policies in international matters, and in the 1870s the United States began publication of a series of documentary volumes, Foreign Relations of the United States (continuing to this day) which set a high standard of diplomatic openness.
World War I certainly raised the stakes in regard to public interest in foreign affairs, and also in regard to the release to the public of diplomatic documents. Throughout the conflict, the belligerents hurled documentary evidence, as well as grenades, at one another (White Books, Blue Books, etc.), and when the carnage finally ended, the German government published a large collection of diplomatic materials, Die Grosse Politik der Europdische Kabinete, originating from as early as the 1870s, in an effort to demonstrate that Berlin did not bear sole responsibility for the diplomatic and military tensions that culminated in the outbreak of war in August 1914.
In the run up to World War II, the British government, in a series of Blue Books and documents, put its diplomatic case before the public regarding World War I and the tensions which would lead to another world war. Other major powers followed suit, while America continued to produce volumes in the Foreign Relations series, though the volumes appeared at less regular intervals and the dates of publication fell ever further behind those of the events recorded in the individual volumes.
Post World War II saw yet another outpouring of British and American diplomatic documents, as well as those of other countries, including collections by the French, the Poles, and the Soviet Union. In addition, a combined Anglo-French-American series of documents on German foreign relations began to appear in the 1950s. This publication effort was made possible by the massive capture of German Foreign Office and other archives in 1945. However, the most novel, as well as one of the most influential, series of post-World War II documents released to the public was the multi-volume collection of Nazi records in the main Nuremberg War Crimes Trial (the IMT), as well as the documents produced by the 'little Nuremberg' trials held in the American zone of Germany and the Japanese war crimes trials conducted in Tokyo by the United States and some of its wartime allies.
These immediate post-World War II documentary releases were unprecedented in regard to the quantity and quality of the material made available to the public, and the depth of insight these documents provided into the inner working of the Axis and Japanese wartime governments. Consequently, public opinion in many countries became less patient with governmental secrecy and informational manipulation. Western governments, in particular, soon discovered that they had little choice but to draw a sharp contrast between themselves and those governments, whether past or present, which had wrapped themselves tightly in policies of secrecy. Rules of access to historical documents were relaxed in Britain, the United States, the Dominions, and other Western countries. Withholding periods were also frequently shortened, and beginning in the 1970s, as post-Vietnam War pressures for greater openness appeared, archival expansion occurred, with the opening of the new Public Record Office in Kew (Surrey) in 1978 and, most recently, the opening of the US National Archives complex in College Park, Maryland.
To top off the post-World War II Anglo-American march toward greater access to archival materials, in the 1970s the US Congress (responding to Vietnam War pressures as well as those occasioned by the Nixon scandals) passed a series of Freedom of Information (FOI) Acts. These measures were intended primarily to reduce public suspicion of governmental secrecy and possible malfeasance, but they ultimately made research work in US archives easier and more fruitful. Furthermore, the steps toward greater openness prompted by FOI in American archives inevitably had a knock-on effect in the archives of other countries, especially those of Great Britain and the Dominions. By the 1980s, nearly all English-speaking countries had some form of 25- or 30-year rule which declared that records of historical value had to be preserved and that many of them must be open for study within a period roughly corresponding to a quarter of a century.
During the Cold War, of course, the Anglo-American governments withheld with one hand what they promised to supply the public with the other. Usually citing communist security threats and the necessities imposed by the stand-off with the Soviet Union, the governments of the United States, the British Commonwealth, and other Western countries withheld not only a large percentage of documents relating to postwar East-West politics, armaments and planning, but also documents from earlier periods which might conceivably provide hints regarding the organization, equipment, personnel and methods employed by Western states in the great Cold War confrontation. Records relating to intelligence sources and methods were considered especially sensitive.1
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1. Nonetheless, excellent research on secret intelligence was carried out in the Cold War era. See, for example, the brilliant pre-New Release article by John Ferris, 'Whitehall's Black Chamber: British Cryptology and the Government Code and Cypher School, 1919-1929', Intelligence and National Security 2/1 (Jan. 1987) pp.54-90.
Once the Soviet Union collapsed, however, the contrast between the broad Anglo-American commitment to archival openness and the prevailing practice of extensive exceptions to the 25- and 30-year rules was impossible to maintain and justify. Understandably, the authorities in London and Washington pleaded for time and patience because the logistics of transferring millions of documents to archival institutions was formidable. Also, the necessary screening and declassifying of these documents, especially those relating to intelligence operations, required time and care. Still, well before many of the doubters believed likely, new releases began to appear in the Public Record Office, the National Archives, and the presidential libraries from Hyde Park, New York to Abilene, Kansas. Fortunately for intelligence historians, from the very beginning of this process the releases included significant collections of intelligence materials.
In the United States historical records of the military and naval intelligence services and the Central Intelligence Agency were among the first to pass into the custody of the National Archives. By the mid-1990s, American historians were completing studies in intelligence history based on new releases by the US government.2 Even Russian scholars began publishing studies of intelligence in the West.3 The taste of intelligence documents whetted the appetites of historians, who were soon debating in scholarly journals questions about the pace and extent of declassification.4
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2. For example, John Prados, 'United States Intelligence and the Japanese Evacuation of Guadalcanal, 1943', Intelligence and National Security 10/2 (April 1995) pp.294-305.3. Zubok Vladislov, 'Soviet Intelligence and the Cold War: The "Small Committee" of Information, 1952', Diplomatic History 19/3 (1995) pp.453-72.
4. See Zachery Karabell and Timothy Naftali, 'History Declassified: The Perils and Promise of CIA Documents', and J. Kenneth McDonald, 'Commentary on "History Declassified" ', Diplomatic History 18/4 (1994) pp.615-34.
In Britain (in a rather more hesitant and idiosyncratic form than in the US) assorted intelligence records began to find their way into the public domain through new releases to the Public Record Office in the late 1980s and the early 1990s. In contrast to American practice, British releases tended to occur in dribs and drabs as the custodial departments gradually worked their way through mountains of withheld documents. Small collections of documents (in some cases single files) were cleared for release as the originating departments accepted that the end of communism meant the end to the sensitivity of some documents. At the PRO such files were brought to the attention of researchers by their inclusion in a series of 'New Release' shelf lists placed in the first floor foyer at Kew and, more recently, by announcements on the PRO electronic website.
In the British system, when a whole class of documents was released, such as the 3,785 files containing the Bletchley Park materials (and other related 'special intelligence' items) passed to Prime Minister Winston Churchill between 1940 and 1945 (HW 1), the researcher need only identify the relevant shelf list and check the items which are chronologically listed therein.5 To determine, however, that ADM 223/213 is a new release and that it deals with No.30 Commando operations aimed at German signals intelligence targets (intercept stations, cipher equipment, etc.) is more difficult because the regular shelf lists at Kew are comprehensive and do not indicate when any particular file was released. It is, therefore, necessary to consult the 'Accelerated Openings' lists (which are currently on a lower shelf behind the desks of the reference archivists in the document ordering room) to establish definitely whether or not any particular file is a new release, because some open files which contain highly sensitive material have simply been released under the 30-, 50-, or 75-year rules and their appearance at this time owes nothing to the end of the Cold War security program.
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5. Two extensive discussions of HW 1 appeared in Intelligence and National Security 10/3 (July 1995): Robin Denniston, 'Diplomatic Eavesdropping, 1922-44: A New Source Discovered', pp. 423-48 and Kathryn Brown, 'Intelligence and the Decision to Collect It: Churchill's Wartime Diplomatic Signals Intelligence', pp.449-67.
For example, one might assume that ADM 1/8577/349 was a new release since it concerns Government Code and Cypher School (GCCS) staffing from World War I to 1922. In fact, this file was opened in the 1970s under what one might call the quite sensitive 50-year rule, and has been available to researchers for two decades.
On the other hand, ADM H 6/6298 and 6319, which cover Communism in the Royal Navy during the 1930s, probably Would have remained closed for a great many more years than they have, if the collapse of the Soviet Union had not made the dangers posed by communist activities, past and present, largely irrelevant.6
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6. My thanks to Mrs Anne Crawford, PRO Kew, for assistance on this question. Those cruising the PRO on a regular basis may wish to employ another method. By turning the regular shelf lists on end it is frequently possible to spot new, white, pages. This is usually a good indication that a new release is lurking somewhere on such a page. This method is only effective for a brief period, for soon wear, tear, and weathering leave pages with new releases on them indistinguishable from others. At that point only the 'Accelerated Openings' lists can offer succor.
Such anomalies and complexities in the British document classification and release system may strengthen the belief of some observers that, compared to the United States, Britain has remained tight-fisted regarding intelligence releases. This view may be further strengthened by recent releases undertaken by the US National Security Agency. In the 1980s NSA began declassifying in-house cryptologic studies (the SRH series in NARA's Record Group 457), but the releases were infrequent and the documents often redacted. In 1996, however, the agency released to the National Archives, College Park, 1,471 boxes of cryptologic documents from the period 1914-45. The file list, which extends to over 50 pages, establishes this spectacular accession as the largest 'Top Secret' or 'Top Secret Ultra' collection of documents yet released by any government.
Even as we express surprise and gratitude for this act of American largesse, it is important to note that British authorities have also made very significant documentary disclosures in the area of cryptologic history, and these releases are continuing.7 Because they have been so secret so long (and because of their great volume), British documents relating to Room 40 in World War I and the inter-war period which are included in this declassification program are perhaps the most exciting for historians. The series begins with Winston Churchill's opening directive to Room 40 of 8 November 1914 (in HW 3/4) which states that a war staff 'should be selected to study all decoded intercepts', not only to secure specific military and naval information, but also to 'penetrate the German mind'. The 183 files in HW 3 include many other treasures, such as Alastair Denniston's secret in-house history of British cryptanalysis (HW 3/32-3) and the papers of W. F. Clarke (HW 3/34-69).
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7. See Richard J. Aldrich, 'The Waldegrave Initiative and Secret Service Archives: New Materials and New Policies', Intelligence and National Security 10/1 (Jan. 1995) pp. 192-7.
Although five files covering the Zimmermann telegram (in HW 7/8) remain closed, as does a War Office file regarding 'American Relations with Germany, May 1915-April 1916' (WO 106/6072), the original decrypt of the Zimmermann telegram (in HW 7/8) shows that the decoder (who may well have been Nigel de Grey) initially failed to break the crucial passage of the text. In that passage Zimmermann's message suggested that Germany would support Mexico's annexation of Texas, Arizona and New Mexico if the United States entered the war on the side of the Allies. When London provided the text of the complete telegram to Washington, this was the passage that most angered President Woodrow Wilson and subsequently inflamed American public opinion. Apparently, second attempts in cryptanalysis on some occasions do pay off!
On the other side of the political coin, however, the recently-released Room 40 official histories (HW 7/1-34) clearly show that British authorities read a large number of American diplomatic messages in 1916, including those of Washington's ambassador in London, Walter Hines Page. At least 75 American diplomatic messages to and from US missions around the world were read by the British before April 1917.
Fifty-six Admiralty files (ADM 223/735-791) contain additional material on Room 40 and diplomatic cryptanalysis between 1914 and 1918. These files include George Young's seven page 'inside history' of the political branch of the organization which provides several interesting revelations, such as the effort by the Germans in May 1917 to enlist Sun Yat-sen's support on behalf of the Central Powers.
Regarding the interwar period, a large number of GCCS documents can be found in HW 3/34-69, 79, and 82-3, as well as the volumes of HW 12, which contain diplomatic decrypts from 1919 to 1926. This series is especially revealing because it reveals that Britain penetrated nearly every post-World War I diplomatic code or cipher system, including those of France, the Soviet Union, and the United States. Greece and the United States were the only two governments whose diplomatic cryptosystems were so thoroughly penetrated that copies of their decrypted messages appear in every one of the 78 volumes in this series. In contrast, though the series contains many decrypts of Soviet diplomatic and agent traffic from the early postwar period, 19 of the 78 volumes contain no Soviet material at all. The release of such material, especially files revealing that GCCS efforts against American codes and ciphers may have been more extensive and successful than those against Japanese and Russian, should give a historian pause. Certainly diplomatic historians will need to reconsider some prevailing interwar truisms, especially those related to the foundations of British power and the range of its diplomatic activities and achievements.
The scope and depth of these cryptanalytic revelations concerning World War I and the early interwar period might lead a historian to conclude that any revelations about World War II in recently released files will be less significant. Such a conclusion would be understandable because of earlier British and American releases and because the excellent official history of British intelligence in World War II has long been in the public domain and many scholars assume that these books tell the bulk of the story.8 Again, however, it is the sheer volume of the new intelligence releases which makes it obvious that the signals intelligence history of 1939-45 will have to be seriously reconsidered.
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8. F.H. Hinsley, E.E. Thomas et al., British Intelligence in the Second World War, Vols.1-4 (London: HMSO 1979-90), plus V61.5, Strategic Deception by Michael Howard (London: HMSO 1990).
The recent releases concerning British signals intelligence in World War II include an impressive amount of naval materials. The history of the wartime naval section at Bletchley Park (W.E. Clark papers) extends through files 19-25, 27-30, and 33-38 in HW 3. The naval section's daily activity records are in files 103-06, 109-11, and 114-13 8 of the same series. The first 12 files of HW 8 cover additional aspects of British naval cryptanalysis. The ADM 223 Admiralty intelligence series is also rich in Sigint material from World War II, with extensive documentation appearing in files 369-70, 384-5, 469-70, and 479. The same series has three files (293-4 and 296) on the 'Anderson' Far Eastern cryptanalytic centre, as well as four series on the Operational Intelligence Centre, files 310ff, 371ff, 402-3 1, and 435-440. Two series of documents on the history of the Naval Intelligence Division (files 298 and 464ff) are also available, along with two collections of its director Rear Admiral John Godfrey's papers in ADM 223 (files 297ff and file 619). The ADM 223 series also contains a large run of files (264-283) on naval 'Y'. Additional 'Y' material is available in ADM 116, files 6320 and 6322-24, and ADM 1/27183. There is also at least one file (ADM 1/27186) on British naval cipher security.
Until September 1996, releases dealing with naval Sigint far exceeded those dealing with army and air force activities. The recent opening of 585 files of GCCS German section decrypts of Luftwaffe and German Army messages for the period February 1940-September 1944 changed all that. In addition, military intelligence records in WO 208/5070-1 include a 30 January 1942 report on 'military intelligence at GC and CS' by Brigadier W. E. Custem together with an account of the February 1942 reorganization of GCCS. WO 208/1988 contains Turkish decrypts, and HW4 (files 1-25) includes considerable military material in its coverage of GCCS decrypts from the Far East. A large number of British Army 'Y' files are available in WO 208 (files 5020-5069, 5073-5136). A memorandum of I November 1941 in WO 208/5069 records that 324 Army radio sets were required to intercept Enigma.
Recent releases of Royal Air Force signals intelligence seem to be comparable in volume to those concerning the British Army. In addition to Nigel de Grey's valuable history of air Sigint in the war (HW 3/94-102), a collection of Bletchley air section files has been released in HW 3 (files 103-06, 109-11, 114-33). The Cheadle intercept station war diaries, which contain much Sigint information, are in the HW 2 series, while RAF 'Y' appears in AIR 40, especially files 2355, 2367-8, 2583-4, 2615, 2617, and 2663-67.
In contrast to the broad range of military, naval, and air special intelligence records from World War II which have recently become available, British wartime materials related to diplomatic cryptanalysis (aside from HW 1) remain, at this point, relatively scarce. Some diplomatic materials exist in HW 3, especially files 78-83, and some Japanese diplomatic traffic from 1945 is in HW 10/1-3. In addition, such general administrative matters as the internal organization of Bletchley Park and postwar planning for GCCS appear among the recent releases (WO 208/5069 and 5071, as well as HW 3/164-175). Still, a broad wartime diplomatic series remains unavailable in the PRO, a deficiency only partially offset by HW 11, an overarching series (38 files) which deals with virtually all aspects of the work of GCCS in 1939-45.
This large and diversified body of World War II materials has not been opened in one huge block in the American manner, but in relatively small groups of files. This procedure arose mainly from the effort of the Public Record Office to keep groups of records as much as possible within an organizational arrangement corresponding to each department's own record system. As the current releases demonstrate, Britain's most sensitive intelligence activities in World War II (especially following the failure of Admiral Godfrey's Bletchley reorganization efforts in 1941) were spread much more widely across departments than has heretofore been recognized.9 The inevitable result of this combination of shifting policies has been that many of the records of Britain's most secret intelligence activities have been distributed across a larger number of record groups in the Public Record Office than the corresponding materials in the US National Archives.
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9. On the general point, see WO 208/5070-01 and HW 3/167-75. For Adm. Godfrey, see WO 208/5069.
Inevitably, the new release system employed in the Public Record Office may on occasion seem repetitive and muddled to those trying to find Ultra materials at Kew. Despite such bits of confusion and frustration, the British accelerated release system demonstrates the benefits to a democratic society of a free and open archival system. The treasures now on offer are so rich and extensive that those interested in serious intelligence history will find their exploratory efforts richly rewarded. Thus armed, they should be able to slay many of the mythical dragons that have grown up in the green pastures of popular historical writing since the end of World War II.
Axis Sigint Collaboration: A Limited Partnership
DAVID ALVAREZ
In the 1920s German cryptanalytic agencies began to establish cooperative
relations with sister services in many of the countries that would fight
alongside Germany during World War II. After the outbreak of war, collaboration
intensified and resulted in a few notable successes against Allied and neutral
communications. Collaboration was undermined, however, by inadequate resources,
ineffective coordination, and the condescension of the Germans, who treated
their putative allies as dependents rather than equals.
Automating American Cryptanalysis 1930-45: Marvelous Machines, a Bit Too Late
COLIN BURKE
This essay traces the efforts of American and German cryptanalysts to construct
advanced code and cipher breaking machines before and during World War II.
Extending the reach of the 1995 book, Information and Secrecy, this paper
reveals that the Americans built more advanced machines than thought, Such
as the 5202 for the 'Fish' problem. However, that and their other machines
Usually emerged too late to meet the targeted crypto-crises -- partly because
of the failure to sustain a program of the mid- 1930s. The German program
began much later and was much less productive than the American or British
initiatives.
Signals Intelligence in Australia during the Pacific War
FRANK CAIN
When the Pacific War commenced in December 1941 Australia and its Allies knew little about how to break Japan's military codes. The US Navy was better prepared to read Japan's naval codes and when General MacArthur escaped to Australia with his Sigint staff they combined with the Australian decoders who had worked against the Germans in the Middle East to form the Central Bureau. Slowly and persistently these operators broke Japan's air codes, water transport codes and later the main army code. This analysis explains how this decoding knowledge was slowly accumulated and how it contributed to the ending of the war.
New Evidence on Breaking the Japanese Army Codes
EDWARD J. DREA and JOSEPH E. RICHARD
The Imperial Japanese Army developed an extremely complex yet user- friendly code system that was, in theory, unbreakable by outsiders. A combination of Japanese systemic errors in transmitting enciphered messages and poor physical security when handling code materials enabled the Allies to break what was one of the most difficult book-based cryptosystems of World War II. Recently available declassified American documents amplify and clarify the Imperial Army's use and abuse of its code systems in the Southwest Pacific Theater with specific wartime examples that illustrate how the Japanese army codes unraveled.
The 'Usual Source': Signals Intelligence and Planning for the Eighth Army
'Crusader' Offensive, 1941
JOHN FERRIS
This in-depth study looks at the intelligence process before Eighth Army's
first defeat of Rommel in North Africa at the end of 1941. In particular
the role of Brigadier John Shearer, the Army's intelligence chief, is examined
in relation to Generals Wavell, Auchinleck and Cunningham. Shearer's increasingly
professional methods, however, could not deliver an easy victory for Eighth
Army in its bid to relieve Tobruk.
Cautious Collaborators: The Struggle for Anglo-American Cryptanalytic Co-operation, 1940-43
LEE A. GLADWIN
'Cautious Collaborators' recounts the halting development of British-United
States cryptanalytic collaboration from first tentative contacts and troubled
arrangements through the conclusion of the Wenger-Travis agreement (1942)
and the British and United States Agreement (BRUSA) of 1943. It sheds new
light on the tangible results of the Abraham Sinkov mission and details the
impact of Alan Turing's United States visit on the conclusion of BRUSA.
Searching for Security: The German Investigations into Enigma's Security
R. A. RATCLIFF
'Search for Security' examines why the German Marine (Navy) never recognized
the compromise of its Enigma ciphers. The detailed study of several surviving
Marine security investigations reveals that the investigators employed flawed
methods and refused to consider seriously rather obvious signs that the Allies
could read Enigma messages. Instead, the Germans blamed their information
leaks on Allied agents and, most of ali, on the Allies' presumed technical
superiority in the areas of radar and location technology, not superior
cryptanalytic technology.
New Intelligence Releases: A British Side to the Story
BRADLEY F. SMITH
Signals Intelligence and Vichy France, 1940-44: Intelligence in Defeat
MARTIN THOMAS
After the 1940 defeat, French Sigint activity continued under the Vichy regime. It remained primarily devoted to the interception of Axis signals although, across the Vichy empire, more diverse threats, including the possibility of Anglo-American or Free French incursions in Africa and the Middle East, led to intelligence-gathering against both the Axis and the Allied powers. During 1942 French Sigint work fell victim to the political divisions within the civil-military hierarchy at Vichy, and was undermined by the Axis occupation of southern France in November. Still, the former emphasis on anti-Axis intelligence-gathering and the involvement of senior Vichy leaders in the continuation of Sigint activity suggest that the regime was less resigned to defeat and eventual collaboration than is often supposed.
Chinese Codebreakers, 1927-45
MAOCHUN YU
This study traces the origins of Chinese codebreaking efforts during the key years of the Republican period. It deals with China's Sigint against the invading Japanese, its political implications within the KNIT power structure, China's tenacious attempt at breaking the Japanese military code and its success, and finally, and more importantly, China's codebreaking efforts in the grand scheme of Allied war operations in East and South Asia, with the special emphasis on Chinese-British Sigint cooperation or the lack of. The Chinese story once again testifies to the importance of inter-service and inter-ally coordination, the failure of which contributed to many disasters during World War II in Asia, including the sinking of HMS Prince of Wales and HMS Repulse.