Pearl Harbor advance-knowledge conspiracy theory

The Pearl Harbor advance-knowledge conspiracy theory is the argument that U.S. Government officials had advance knowledge of Japan's December 7, 1941, attack on Pearl Harbor. Ever since the Japanese attack there has been debate as to how and why the United States had been caught off guard, and how much and when American officials knew of Japanese plans for an attack. In September 1944, John T. Flynn, a co-founder of the non-interventionist America First Committee, launched Pearl Harbor revisionism when he published a forty-six page booklet entitled The Truth about Pearl Harbor.

Several writers, including journalist Robert Stinnett, retired U.S. Navy Rear Admiral Robert Alfred Theobald, and Harry Elmer Barnes have argued various parties high in the U.S. and British governments knew of the attack in advance and may even have let it happen or encouraged it in order to force America into the European theatre of World War II via a Japanese–American war started at "the back door". Evidence supporting this view is taken from quotations and source documents from the time and the release of newer materials. However, the Pearl Harbor advance-knowledge conspiracy is considered to be a fringe theory and is rejected by most historians.

The U.S. government made nine official inquiries into the attack between 1941 and 1946, and a tenth in 1995. They included an inquiry by Secretary of the Navy Frank Knox (1941); the Roberts Commission (1941–42); the Hart Inquiry (1944); the Army Pearl Harbor Board (1944); the Naval Court of Inquiry (1944); the Hewitt investigation; the Clarke investigation; the Congressional Inquiry (Pearl Harbor Committee; 1945–46); a top-secret inquiry by Secretary of War Henry L. Stimson, authorized by Congress and carried out by Henry Clausen (the Clausen Inquiry; 1946); and the Thurmond-Spence hearing, in April 1995, which produced the Dorn Report. The inquiries reported incompetence, underestimation, and misapprehension of Japanese capabilities and intentions; problems resulting from excessive secrecy about cryptography; division of responsibility between Army and Navy (and lack of consultation between them); and lack of adequate manpower for intelligence (analysis, collection, processing).

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