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Microform: The MAGIC Documents: Summaries and Transcripts of the Top-Secret Diplomatic Communications of Japan, 1938-1945

Identity Statement

Reference code(s): GB 0099 KCLMA MF 388-401
Held at: Liddell Hart Centre for Military Archives, King's College London
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Full title: Microform: The MAGIC Documents: Summaries and Transcripts of the Top-Secret Diplomatic Communications of Japan, 1938-1945
Date(s): 1938-1945, 1982
Level of description: Collection (fonds)
Extent: 14 reels
Name of creator(s): Signal Intelligence Service, US Armed Forces; Far Eastern Section, Military Intelligence Service, US Armed Forces; Special Branch, Military Intelligence Service, US Armed Forces


Administrative/Biographical history:

MAGIC was the codeword used by the United States to identify deciphered Japanese diplomatic communications immediately prior to and throughout World War Two. During the war, the term MAGIC was also used for deciphered Japanese military communications, as was the term TOP SECRET ULTRA. The documents in this collection are restricted to diplomatic communications. MAGIC included all decrypted messages in Japanese diplomatic codes and ciphers, the most valuable of which were those encoded by the cipher machine known to the US as PURPLE. The ability to break into PURPLE meant that the Americans were able to read the most secret of Japanese diplomatic communications from before the Japanese attack on Pearl Harbor, 7 Dec 1941, to the end of the war in the Pacific. By way of the Japanese ambassador to Berlin, Lt Gen Hiroshi Oshima, MAGIC intelligence also provided information throughout the war about German plans and operations against the Soviet Union and the Allies. The PURPLE cipher machine was used by Japanese diplomatic and military personnel and operated by substituting ordinary typewriter keys, through a series of stepping switches and electrical matrices, into substitute letters. Theoretically, the possible substitutions by the machine cipher were endless and thus difficult to crack. Through MAGIC, however, American cryptanalysts found beachheads into Japanese ciphers from phrases used regularly and repeatedly and available in plain text. Leading the US attempt to break PURPLE was William F Friedman, a cryptanalyst who successfully broke German codes during World War One. Friedman was an expert in statistics an probability and, aided by a cryptanalyst from the US Navy, Harry L Clark, and a team of mathematicians, he successfully cracked the PURPLE code on 25 Sep 1940. Once the Freidman group enciphered PURPLE, they constructed four machines to duplicate its functions and distributed them to Washington, DC, the Philippines, and Bletchley Park, Great Britain. Upon receipt of the PURPLE machine, the British began decrypting diplomatic messages to and from Japanese embassies in Europe, the Far East and the Middle East and, by Jun 1941, had received a second machine for Singapore. Although it revealed the imminence of the war, MAGIC had little operational value. It did not reveal Pearl Harbor as a target of attack, as Japanese diplomats were often not briefed on military plans. MAGIC did, however, reveal Japanese intentions in 1941 of breaking off negotiations with Washington and London, hence indicating plans for war. Through the coded traffic of Japanese ambassador to Berlin, Hiroshi, the Allies were notified of a possible German invasion of the Soviet Union in the summer of 1941, German apprehensions of waging war on more than one front, and German troop dispositions against the Allied invasion of France in Jun 1944. MAGIC's final operation of the war was its revelation to the Allies of Japan's desperate effort to secure Soviet mediation of the war in the Pacific.


Scope and content/abstract:

The MAGIC Documents: Summaries and Transcripts of the Top-Secret Diplomatic Communications of Japan, 1938-1945, is a themed microfilm collection relating to US deciphers of Japanese diplomatic codes through the use of MAGIC decryption, 1938- 1945. The collection contains copies of deciphered official and unofficial Japanese diplomatic communiqués sent from Japanese personnel stationed at embassies and consulates in the Far East, Europe and the Middle East, to Tokyo, Japan, 1938-1945, and includes material relating to Japanese civil, political and economic conditions and policies, military expenditures, strategy, tactics, and campaigns, and eventual peace initiatives and surrender, 1938-1945. Included in the collection are deciphered messages concerning Japanese perceptions of Allied strategy against Japan; the effect of Allied air raids on Japan; Japanese relations with the German Foreign Office; Japanese relations with the governments of Burma, Indo-China; Korea, Netherland East Indies, Siam, China, the Philippines; perceptions of Allied chemical warfare capabilities; perceptions of Allied Lend-Lease naval forces and strategy; British and French relations with colonies in the Far East; control of industry in Manchuria (Manchukuo); perceptions of Axis strategy and Japan's role within it; Japanese interest in Indian nationalism and the Indian Independence League; the Burma-Siam railway; Japanese attacks on the Burma Road, the supply route which connected Burma to Generalissimo Chiang Kai- Shek's nationalist forces in China; administration of the government of Japanese occupied Nanking, China; the Chinese Communist Party; the rationing of clothing and food in Japan; perceptions of the Soviet Comintern Pact; Japanese relations with German, European, and Chinese banks; Japanese relations with Spanish Gen Francisco Franco Bahamonde, the German High Command and Italian Prime Minister Benito Mussolini; interpretation of the Greater East Asia Co-Prosperity Sphere; concern for Japanese nationals abroad, 1937-1945; Japanese naval strategy and tactics; function of the Japanese Consular Police, China; territorial claims on the Kurile Islands; material relating to Japanese military campaigns during World War Two; Japan's search for strategic resources in the Far East; military strengths and dispositions of the German Armed Forces; the origins of the Russo-Japanese Neutrality Pact; Allied and Axis propaganda methods; the treatment of Allied prisoners of war; the surrender of Japanese armed forces in the Far East.

Access & Use

Language/scripts of material:

System of arrangement:

Arranged into chronological order

Conditions governing access:

Open, subject to signature of reader's undertaking form

Conditions governing reproduction:

Copies may be printed off the microfilm for research purposes and are charged at the cost to the Centre. Enquiries concerning the copyright of the original material should be addressed to University Publications of America, Inc, 4520 East-West Highway, Bethesda, MD, 20814, USA

Finding aids:

Summary guide entry on-line at, and published detailed catalogue available in hard copy in the Centre's reading room, Paul Kesaris and David Wallace, et al, The MAGIC Documents: Summaries and Transcripts of the Top-Secret Diplomatic Communications of Japan, 1938-1945 (University Publications of America, Inc, Bethesda, MD, 1982)

Archival Information

Archival history:

Immediate source of acquisition:

University Publications of America, Bethesda, MD, USA

Allied Materials

Related material:

Publication note:

Description Notes

Archivist's note:

Rules or conventions:

Date(s) of descriptions:
Date of compilation: Sep 1999

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