Magic and Ultra in the China-Burma-India Theater

The U.S. broke the Japanese diplomatic cipher “Purple,” codenamed MAGIC, prior to Pearl Harbor. Decoding success with the various Japanese military codes, codenamed ULTRA, was not achieved until 1943. MAGIC and military (as distinct from naval) ULTRA were the responsibility of the U.S. Army. All MAGIC and ULTRA decrypts were shared with the British. MAGIC and ULTRA were made available to major commanders in the China-Burma-India Theater as they became available. This study makes use of the official U.S. Army history of the theater, intelligence histories, the daily “Magic Summaries,” and ULTRA material to examine the operational use of MAGIC and ULTRA. The study focuses on the Second Burma and North Burma Campaigns while making observations about the Salween Campaign and the British defense of India. The study concludes that neither ULTRA nor MAGIC were able to consistently fathom Japanese intentions in Burma and that the ultimate importance of MAGIC and ULTRA was to confirm intelligence obtained from other sources. Nevertheless, as the war went on, ULTRA revealed more and more of Japanese operational goals.