…..So much official secrecy continues to surround the translations of the intercepted Japanese naval dispatches that it is not known if the foregoing message was sent to McCollum or seen by FDR. It is not even known who originally translated the intercept. One thing, however, is certain: The message’s significance could not have been lost on the translator.
1941 also witnessed the following:
On January 27th, our ambassador to Japan, Joseph Grew, sent a message to Washington stating: “The Peruvian Minister has informed a member of my staff that he has heard from many sources, including a Japanese source, that in the event of trouble breaking out between the United States and Japan, the Japanese intended to make a surprise attack against Pearl Harbor with all their strength….”
On November 3rd, still relying on informants, Grew notified Secretary of State Cordell Hull: “War with the United States may come with dramatic and dangerous suddenness.” He sent an even stronger warning on November 17th.
Congressman Martin Dies would write:
Early in 1941 the Dies Committee came into possession of a strategic map which gave clear proof of the intentions of the Japanese to make an assault on Pearl Harbor. The strategic map was prepared by the Japanese Imperial Military Intelligence Department. As soon as I received the document I telephoned Secretary of State Cordell Hull and told him what I had. Secretary Hull directed me not to let anyone know about the map and stated that he would call me as soon as he talked to President Roosevelt. In about an hour he telephoned to say that he had talked to Roosevelt and they agreed that it would be very serious if any information concerning this map reached the news services…. I told him it was a grave responsibility to withhold such vital information from the public. The Secretary assured me that he and Roosevelt considered it essential to national defense.
Dusko Popov was a Yugoslav who worked as a double agent for both Germany and Britain. His true allegiance was to the Allies. In the summer of 1941, the Nazis ordered Popov to Hawaii to make a detailed study of Pearl Harbor and its nearby airfields. The agent deduced that the mission betokened a surprise attack by the Japanese. In August, he fully reported this to the FBI in New York. J. Edgar Hoover later bitterly recalled that he had provided warnings to FDR about Pearl Harbor, but that Roosevelt told him not to pass the information any further and to just leave it in his (the president’s) hands.
Kilsoo Haan, of the Sino-Korean People’s League, received definite word from the Korean underground that the Japanese were planning to assault Hawaii “before Christmas.” In November, after getting nowhere with the State Department, Haan convinced Iowa Senator Guy Gillette of his claim’s merit. Gillette briefed the president, who laconically thanked him and said it would be looked into.
In Java, in early December, the Dutch Army decoded a dispatch from Tokyo to its Bangkok embassy, forecasting attacks on four sites including Hawaii…….