1. The U.S. government had no knowledge of a potential Japanese attack before Dec. 7.
Beyond the obvious signs of Japan’s increasing aggression — including its sinking of an American naval vessel in the Yangtze Riverand its signing of the Tripartite Pact with fascist Italy and Nazi Germany — various specific war warnings had been sent by Washington to military commanders in the Pacific for some days before Dec. 7.
The War Department had been intercepting and analyzing secret cables between Tokyo and the Japanese Embassy in Washington and thought at one point that the Japanese would attack Hawaii on Sunday, Nov. 30. A Hawaii newspaper even warned, in a blaring headline, of a possible attack.
On Dec. 4, Roosevelt received a 26-page memo marked “Confidential” from the Office of Naval Intelligence detailing Japanese espionage efforts. The possible outbreak of war is mentioned, followed shortly by this paragraph: “The focal point of the Japanese Espionage effort is the determination of the total strength of the United States. In anticipation of possible open conflict with this country, Japan is vigorously utilizing every available agency to secure military, naval and commercial information, paying particular attention to the West Coast, the Panama Canal and the Territory of Hawaii.”
