The Ambassador in Japan (Grew) to the Secretary of State
TOKYO, January 27, 1941—6 p.m.
[Received January 27—6: 38 a.m.]
125. A member of the Embassy was told by my———————colleague that from many quarters, including a Japanese one, he had heard that a surprise mass attack on Pearl Harbor was planned by the Japanese military forces, in case of "trouble" between Japan and the United States; that the attack would involve the use of all the Japanese military facilities. My colleague said that he was prompted to pass this on because it had come to him from many sources, although the plan seemed fantastic.
(PEACE AND WAR, UNITED STATES FOREIGN POLICY 1931-1941, UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON: 1943)