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Seminar paper
Japanese military historical sources after the war: a brief survey
Professor TANAKA Hiromi

As every schoolboy knows, Germany surrendered in May and Japan in August 1945, but there was a major difference in the circumstances of each surrender. In Germany the Allied forces advanced to Berlin and completely crushed German military resistance; in Japan the Emperor surrendered just as the Allied forces began their campaign to invade Japan.

The difference between the German and Japanese surrenders had a profound influence on each country’s documentation of the army, navy and the war in general. The rapid pace of the Allied advance through Germany meant that a large quantity of historically important material was requisitioned before it could be destroyed. In contrast, Japan had plenty of time to dispose of its records between the announcement of the surrender on 15 August and the landing of Allied forces on 30 August.[1] During this period some 2.5 million Japanese troops remained under the command of the Japanese armed forces, and before the arrival of the Allies they undertook the “Great Incineration Operation” ordered by the government. There is no evidence that measures to stop this destruction of records were taken by the Allies even after their arrival in Japan, though a “strong recommendation” against further destruction was apparently issued from GHQ (according to the Washington Document Centre).

One can only guess at the percentage of documents that was destroyed in the ten weeks between the surrender and the order to halt the incineration. When considering this question in the past I estimated that 99 per cent was incinerated, but I have come to think recently that it is closer to 99.9 per cent. Even the remaining 0.01 per cent has not received adequate historical examination because this period has traditionally been the preserve of political scientists. Recently, however, it has at last become possible for historians such as myself to make advances in this field and to establish the whereabouts of these materials.

1. Wartime documents: categories and locations

Documentary material in Japan at the time of the occupation by the Allies can be divided into three categories:

1. documents removed to safety to escape bombing raids during the war;
2. documents recovered just before their incineration;
3. documents removed informally and hidden in private homes etc.

The first two categories of documents were requisitioned by the Washington Document Centre (WDC) of the US Army. The WDC was an information gathering organisation that developed out of the Military Document Centre (MDC). In 1945 it planned the “Operation Blacklist” which aimed to collect essential material for war crimes trials in both Germany and Japan.

The WDC began its activities in Japan at the beginning of November 1945. With the cooperation of US Army and Navy organisations such as the Allied Translation and Interpretation Service (ATIS), JICPOA, SEATIC, SHAEF and others, it collected a considerable amount of material between March and August 1946. According to a WDC record entitled “Operation of MIS,” the total number of items collected was 477,894, but the identification numbers assigned by ATIS, the organisation in charge of sending the material to the US, reached as high as 704,583. Although details are unknown, agencies other than WDC were involved in the collection of documents, including the Map Service of the US Army; Macarthur’s so-called private historian, George Prange; and Samuel Morrison, who had been commissioned by the US Navy to edit the official History of US naval operations during World War II.

As it turned out the material collected by the WDC was not used for war crimes trials. Official documents, mainly the Japanese Army’s Dainikki (Great Diary) and the Navy’s K˘bunbik˘ Rui (Archival Records) were placed under the control of the National Archives Record Service (NARS). The US Central Intelligence Group (CIG) was given control of material of high information value, while the Library of Congress had general jurisdiction over other printed matter. CIG was later absorbed by the CIA, as were the documents under its control, which included material that would later prove useful to the US during the Korean War, such as surveys of Soviet military strength in Siberia and Chinese military strength in Manchuria. At the end of the Korean War these documents were transferred to the Library of Congress, bringing its share of WDC documents to 80-90 per cent.

2. Returning the WDC documents to Japan

From the beginning of 1953 the Japanese government began to petition the US government for the return of the documents confiscated in Operation Blacklist. An examination of these requests reveals that only the official documents held by NARS were being sought by the Japanese at this time. Strangely enough, the documents in question had been left in their boxes and stored in a torpedo warehouse in Washington. Why the return of the material in the Library of Congress was not sought remains a puzzle; perhaps the common but misguided preconception that handwritten material was more valuable that printed material was a factor.

After four years of negotiation it was decided to return the WDC materials to Japan. In anticipation of their arrival, a plan was made to microfilm the more important documents, with funds provided by the Ford Foundation and prominent academics such as Clarence Wilbur, Edwin Reischauer, James Moreley and Edwin Beal. Where some of the documents were duplicated, it seems that these scholars could have removed some of the duplicates for their own academic institutions. Some of the more fragile materials were also destroyed by the microfilm process.

The remaining documents were eventually sent to Japan in March 1958. The number of items returned was 21,926, 30 per cent less than the Japanese were expecting. The returned documents were received by the Ministry of Defence War History Office, which had been formed during the negotiations for the purpose of compiling an official history of the Second World War. Among the returned documents were discovered a variety of non-related magazines and technical materials published during the war in countries other than Japan. These were considered non-essential and were eventually transferred to other institutions, if not thrown away. In subsequent investigations into the matter, the War History Office realised that there was still a considerable number of Japanese documents in the US, and in 1965 it launched another petition to secure their return. Because of an amendment in legislation just prior to the repatriation of these documents in 1967, all of them were eventually claimed by the National Archives.

3. Document types (1): WDC documents and their contents

The majority of WDC documents repatriated to Japan consisted of materials removed to safety during and just after the war; most of them relate to the Japanese Army and Navy. The majority of these documents are classified as fairly low-priority, low-sensitivity items, particularly in relation to the question of Japan’s responsibility for the war. Indeed, very little of the material requisitioned by the Allies can be judged to bear on any aspect of Japan’s war responsibility. Many documents relate to annuity calculations for commissioned and non-commissioned officers, others to the military mobilisation plan and budgets, but these are relatively few in number. Overall, the view of history to be gained from these documents is limited in scope.

It can now be confirmed that the material subsequently returned to Japan, as well as some 7,000 items in the Japanese Section of the Library of Congress, were part of the materials requisitioned by the WDC. Occasionally there are Japanese reports of the discovery of new materials from this period in locations such as NARS. A large number of items that were transferred to the Library of Congress, however, are now unaccounted for. It seems certain that some of the missing documents were distributed to major universities in the US; while it is possible to trace the documents that were catalogued in university libraries, it is not possible to ascertain the whereabouts or condition of documents that went to various university departments.

Among the materials captured by the WDC, documents on aviation were catalogued and microfilmed by the US Army Experimental Flying Corps at Rightfield air base in Dayton, Ohio. Some 340 reels of microfilms were made, collectively titled German-Japan air technical documents and consisted of 303 reels of German documents and 37 reels of Japanese documents. The German portion of the collection is dominated by applied research materials, while the Japanese documents consist mainly of basic research materials. An interesting feature of this collection is the clear picture it provides of the technological gap between the two countries during the 1930s and 1940s.

4. Document types (2): non-WDC documents and their contents.

Now I would like to refer to the materials collected during the war by US intelligence organisations other than the WDC. One such example would be those searched and recovered from sunken Japanese battleships by US naval divers. I have not yet identified precisely which authority directed the diving operations, making confirmation of the exact number and content of the documents they yielded quite difficult. The best-known such materials are those retrieved from the Japanese cruiser Nachi, now referred to as the Nachi documents. Documents recovered from sunken ships are kept at the Naval Historical Centre in Washington. These dives were probably initiated in the hope of finding strategically significant documents such as cipher code books, but the collection at the Naval Historical Centre contains no documents of this sort.

ATIS was active in Australia and provided information for counter-attacks by the Allied forces. One of the major functions of ATIS was to contribute information to the planning and execution of strategies; to this end it collected all sorts of materials left on battlefields by the Japanese, analysed war records of individual units and service records of commanders and made predictions on Japanese military capacities and expected enemy movements. The ATIS materials thus include a wide variety of documents, including deposit books, servicemen’s pocket books, personal letters and field diaries. It is interesting to note that there was no equivalent of ATIS and its operations among the Japanese forces, perhaps because they were too preoccupied with impending enemy moves.

ATIS collected a vast amount of material, consisting of 1,618 items from New Guinea, 27 tons of documents from Saipan, and approximately 200,000 and 340,000 items from Tinian and the Philippines respectively. When the war came to an end the 1,618 items captured in New Guinea were handed over to the Australian forces, which then controlled the area, and a portion of these documents form a collection at the Australian War Memorial catalogued as AWM 82. Even so, AWM 82 contains only 585 items collected by ATIS, falling far short of the original collection of 1,618. This is because part of the ATIS material from other areas began to be transferred to the Japanese Section of the Library of Congress in 1955, but it is said that the Library was overwhelmed by the number of documents and eventually had them removed in trucks provided by the army. It is not known where these documents were taken: but I have been informed by sources within the Library that they were taken to Hawaii and burned there. I cannot help wondering however, why these documents had to be taken all the way to Hawaii to be burnt, when this could have been done more easily and cheaply in Washington — and accordingly, I have not given up hope that some day the lost ATIS materials will resurface somewhere. In the meantime, however, AWM 82 remains the only known collection of ATIS materials in existence.

5. Compiling histories: documents and interviews in Japan

To sum up the discussion so far, most relevant wartime Japanese military documents and printed matter were burnt, and many of those that escaped destruction when they were seized by the US have gone missing. The lack of primary documents that resulted from this state of affairs was a problem when Japanese authorities turned their attention to compiling official military histories, such as the histories of the Imperial Japanese Army and Navy. When available written or printed information was considered insufficient, there was no choice but to conduct interviews with retired servicemen and to use these interview records to supplement the scarce records.

The importance of oral history is widely acknowledged in Japan. A much debated point is how to create objective and accurate records of interviews. Interviews with repatriated servicemen after the war can be divided into two periods. The first period was when servicemen were interviewed upon their arrival — autumn 1945 to mid-1949. These interviews were arranged by the Demobilisation Ministry (Fukuinsh˘), which supervised a process in which returned servicemen were temporarily detained and interviewed at special facilities at Japanese ports before being allowed to complete their journeys. Both commissioned officers and the rank and file were interviewed during this period. The second period falls between 1960 and 1975, when the National Institute for Defence Studies (NIDS) conducted interviews with former high-ranking officers in order to compile the Senshi S˘sho (Official War History). Since most of these officers were not young men even during the war however, interviewing them some 15-20 years later must have posed difficulties.

Because of their greater reliability the immediate post-war interrogations are more important as historical sources than the later set of interviews conducted by NIDS, so I shall deal with them here in more detail. The 1st Demobilisation Ministry Historical Research Department and the 2nd Demobilisation Ministry Historical Research Department were ordered to conduct research activities by both the G2 section of Allied Occupation Headquarters (GHQ)[2] and the Japanese government. The motives behind the respective orders however, were directly opposed: G2 ordered these departments to collect information that would corroborate Japanese war crimes, while the Japanese government wanted them to collect evidence to establish the innocence of alleged war criminals. Ironically, the Japanese government’s previous order to burn military documents prior to the surrender meant that they were now without adequate evidence to substantiate a defendant’s innocence at the war crimes trials.

For the sake of simplicity, I will refer to both the 1st and 2nd Demobilisation Ministry Historical Research Departments collectively as the Demobilisation Ministry. It endeavoured to retrieve relevant documents remaining in Japan and requested the submission of memoirs or answers to its queries from those who had been involved in the development of important wartime policies and strategies or engaged in the execution of vital projects. The largest project conducted by the Ministry were the interviews with and surveys of servicemen mentioned above.

6. The Demobilisation Ministry interviews

The interviews and surveys were conducted using two methods. First, former servicemen were requested to fill in survey forms during their voyage. None of the survey forms used for this purpose remain in Japan, though four such forms are fortunately included in AWM 82, making them the only examples known to survive. My own research however, has cast doubt upon the accuracy and objectivity of these surveys as historical sources: one of my own former interviewees, for example, remembered being warned by his superior that detailed comments on the survey forms could lead to prosecution as a war criminal. Such fears were not unwarranted. Another story relates how a Japanese serviceman for whom the British forces had issued a warrant was shipped back to Malaya two days after his repatriation, thanks to this survey form, which revealed his name and unit. He never returned to Japan. Many servicemen must have faced similar dilemmas in the repatriation ships: they could not disembark in Japan without filling in the survey forms, but they might be arrested if they revealed their names.

The second method employed by the Demobilisation Ministry involved interviewing Japanese servicemen personally upon their arrival at ports in Japan, detaining them for this purpose at special facilities for two to three days after their arrival. This method yielded fairly detailed records, though I believe that the Demobilisation Ministry employed 100 interviewers at most and that there would not have been so many specialists available from other Ministries with sufficient technical knowledge and experience. It can be assumed, therefore, that only a few dozen interviewers would have been available at each port, explaining why, out of about 2.5 million repatriated servicemen, only ten to twenty thousand were interviewed.

It seems that Japanese ex-servicemen who did not fear being charged with war crimes were the least reticent about their wartime experience. Buoyed by the freedom to speak openly after their release from the yoke of strict military control, many men spoke quite freely on any topic put to them. Some criticised the Emperor, others denounced the leadership and strategies of the Imperial Army and Navy, while many reproached their former immediate commanders. Many interviewees had very accurate memories, despite having had all personal documents confiscated by the Allies once they embarked on the repatriation vessels. Many were able to remember and write down intricate details about the time, date and place where their units engaged in battle, the number of dead and injured, and even the exact amount of fuel and ammunition expended. Perhaps these men thought it their duty, upon returning to Japan, to report their wartime experiences as accurately and fully as possible.

On the other hand, among the returned soldiers who filed these long and detailed reports, there were also many who, when approached again twenty years later, were unable to remember anything about what they had written. While the passage of time, not to mention the release of pent-up nervous tension that would have been experienced directly after they recounted their stories, are likely factors in this amnesia, it does ring warning bells about the accuracy and objectivity of the evidence contained in the interviews. Apart from anything else, the quality of evidence extracted under what must have been stressful circumstances has to be regarded with caution. Be that as it may, no further examination of these interview records is possible, as at some stage in the early post-war period they were transferred to the Ministry of Health and Welfare (K˘seish˘), and their whereabouts is now unknown.

Some information about these records came to light when materials held by Japan’s Ministry of Foreign Affairs concerning war crimes were opened to the public in 1998. Discovered among these documents were some records indicating that a considerable amount of material held by the Ministry of Public Welfare concerning war crimes was transferred to the Department of Justice in 1958, the same year in which Japan’s remaining imprisoned war criminals were set free. Because the Demobilisation Ministry records taken from interviews with returned soldiers were originally compiled to serve as evidence in the war crimes trials, it is certainly possible that these transcripts were also transferred to the Department of Justice, but questions to the Department of Justice about these materials continue to elicit a typically bureaucratic response: the department is “unable to confirm or deny” the existence of the documents!

7. The “Demobilisation war histories.”

It is thought that the Allied forces did not use the records from the interviews in the war crimes trials; whether this was because more reliable evidence was available, or whether judgements were simply handed down without much regard for accurate proof or testimony, remains uncertain. It seems that only the Japanese defence used these documents at the trials. In about 1948 however, GHQ selected about 200 returned soldiers and ordered them to produce reports based on both the interviews and other documents discovered in Japan after the war. Nobody knows exactly who formulated this plan, or for what purpose. All of the reports are between 150 and 200 pages in length, and they contain much valuable data of a highly believable quality, recorded in great detail, and. The first issue of these reports, which I have collectively dubbed the “Demobilisation Ministry war histories”, was published in 1950, and the entire series was completed by 1954. These documents are written entirely in Japanese, but they will soon be available to a much wider audience, as they are currently being re-translated in the United States and will be published on the Internet.

Because the “Demobilisation Ministry war histories” were compiled on the orders of GHQ, each section was probably handed over as soon as it was completed. This history of the war, which was eventually presented to the US Home Office, is currently held by the Asian Division of the Library of Congress. A copy was also given to Britain, where it was recently discovered in the Department of Documents at the Imperial War Museum. Although it is highly likely that a copy was also handed to the Australian authorities, I have yet to establish this. Very little Japanese research has made use of the “Demobilisation Ministry War History,” so it remains quite an important issue for military historians.

8. The Defence Agency history

Predictably, as soon as the Self Defence Agency was established in Japan[3] it set about laying plans to bring out an edited history of the Second World War from the Japanese perspective. The plan came under considerable attack, at first because of its proposed title, which was not “The Pacific War,” but rather “The Greater East Asia War.”[4] The plan also came into conflict with the Demobilisation Ministry’s intentions to obtain the return of official records, on which the history would be based, from the US. In the end, however, the Dainikki (Great Diary) and K˘bunbik˘ Rui (Archival Records), which were repatriated, were mostly administrative documents from the Japanese Army and Navy.[5] These were undoubtedly helpful in compiling a military history dealing with the army and navy between 1870 and 1930, but they are not particularly useful in dealing with the history of the war from 1941.

It was not all bad news. Included in the returned materials were numerous battle reports and official diaries that had been evacuated to Yokohama by the Naval Service Records administration. These made it relatively easy to trace naval activity during the war years. It is also fortunate that the compilation of the history began in 1950, during a time when public consciousness was infused with the optimism and relief that resulted from having been finally freed from foreign occupation. A quite amazing amount of material that had been carefully hidden up to then was suddenly released, including government directives concerning national defence and a number of plans for mobilisation. With the release of these documents a great deal was revealed about the posture and motives of the Japanese military command regarding the war.

Important as such material was, it could not stand alone. It was important that more information be gathered concerning the finer details of individual battles. This sort of information was at first gathered through interviews by Defence Agency personnel and by sending out questionnaires to returned soldiers, but the spiralling costs involved meant that the latter method tended to predominate. Among those questionnaires, gathered more than twenty years after the end of the war, were many that defended Japan’s role in the war.

As I have mentioned before however, the credibility of this type of documentary evidence is somewhat dubious. More deserving of analytical attention are the remaining stock of wartime diaries and memos. During the war some military personnel who remained in Japan kept quite detailed diaries and records. Many of the families of those soldiers who died prior to the end of the war were visited by army and naval officials, in order to check whether the soldier in question had written anything that could be classified as an official document, or which concerned national security in any way. If anything of this description was found it was immediately confiscated, with the result that it has been very unusual to discover historical materials in the families of deceased soldiers, especially those of high rank. Among those who were lucky enough to survive the war, many managed to hold on to their diaries and memos, taking them back home upon repatriation. Many of these items were loaned to the Defence Agency and proved very helpful in compiling Japan’s Official history, finally published in 1978 in 102 volumes.[6] Most of the diaries and memos were returned to the owners, though a few of them were kept by the Defence Agency for its records.

9. The trend towards privacy in Japan, and its effect on accessing documentary sources

In a period when there has been an undeniable trend towards greater protection of privacy in Japan, it has become difficult to regain access to these diaries and memos. Assuming there are no objections from the families concerned, it is still possible to view those which were retained by the Defence Agency, but privacy issues are making it increasingly difficult to gain access even to official documents, particularly those which mention individuals by name. Accordingly, even if the records which are currently suspected of being held at the Ministry of Justice were released, access to them could well remain a problem.

There is another, more serious, issue at stake for those who understand the broader implications of increased privacy protection. During the half century that has passed since the end of the war, the atmosphere has changed considerably in Japan. From the US-style democracy and anti-militarism that characterised political consciousness in the early post-war period, up to about 1960, there has been a notable shift towards justification and even glorification of the “Greater East Asian War.” While personal privacy is of course an important issue, given the current tendency to revisionism in Japanese history, an increasing number of historians have expressed concern that the defence of privacy is being misused to obstruct critical and reflective historical research on Japan’s wartime experience.


In conclusion, I wish to say that my long pursuit of historical materials relating to the war has raised my awareness of how small a proportion of Japan’s historical materials are being preserved for posterity even now. The contemporary political, social and economic trends towards mass consumption and mass destruction in the world appear to have begun to penetrate the world of research. So many records are produced; yet so many of them are also being destroyed, creating the possibility that some day we will come to regret that only a fraction of our post-war memory remains. To do nothing about this situation would be a grave disservice to our future generations, and thus it is my hope that we will yet be able to prevent such a failure in Japan.

Translated by Steve Bullard, Akemi Inoue and Meredith Patton for the Australia-Japan Research Project, March 1999.

The Author

Professor TANAKA Hiromi teaches and researches Japanese military history at Japan’s National Institute of Defence Studies. He has conducted extensive research on primary historical sources concerning Japan’s role in the Pacific War and played a significant role in the cataloguing of AWM 82 materials for the Australian War Memorial. In February 1999 Professor TANAKA was a visiting fellow to the Australia-Japan Research Project, where he presented this paper. The Australia-Japan Research Project gratefully acknowledges the assistance of the Japan Foundation in bringing Professor TANAKA to Australia.


[1] This does not include, of course, the Allied invasion of Okinawa, which began in March 1945. By late June 1945 Okinawa was effectively under Allied control, and became an important base for Allied bombing attacks on Japan proper.

[2] Among the five General Staff Sections of the Occupation, G2 was responsible primarily for the collection of information, particularly that pertaining to the security of the Occupation, and internal policy matters.

[3] Under the “demilitarisation and democratisation” policy of the Occupation, the old Japanese Imperial Army and Navy were completely disbanded. In 1947 however, against the background of increasing Cold War tensions, the Occupation authorised the setting up of a “National Police Agency” which was eventually re-named the Japan Land and Maritime Self-Defence Forces.

[4] The naming of Japan’s war has been a source of ongoing controversy among military historians. In recent years for example, the title Dai T˘a Sens˘ (Greater East Asia War) has dropped from common usage in Japan, attracting criticism from writers such as Ienaga Sabur˘, who has argued that restricting the title of the war to Taiheiy˘ Sens˘ “The Pacific War” diverts attention away from Japanese activities in China and Korea prior to 1941, and emphasises the suffering of Japanese people during the devastating firebombing of Japan by Allied Forces (and eventually of course, the American nuclear attack on Hiroshima and Nagasaki).

[5] For more information on these documents, see MUTA Sh˘hei’s essay in the AJRP-Japan Foundation Paper series, “The lack of an archives tradition in Japan.”

[6] Senshi s˘sho Japan Defence Agency Research Institute Military History Office, 1978. A full copy of this history is held by the National Library of Australia.

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