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.”
These were just general warnings, however, and a huge Japanese armada was able to travel thousands of miles from Japan to Hawaii undetected. The U.S. military and government officials were caught off guard by the attack.
2. On Dec. 7, Japan attacked only Pearl Harbor.
Though the attack on Pearl Harbor was the most crippling and caused the most American losses, Japanese forces also struck the Philippines, Wake Island, Guam, Malaya, Thailand and Midway that day. In the Philippines, the capital fell to the Japanese in January 1942 and U.S. forces surrendered in May. In the Pacific, Wake Island was shelled by Japanese aircraft and ships until Dec. 11, when the Japanese attempted the first of two invasions before the island finally fell.
Guam was bombed and later invaded on Dec. 10. Malaya (now Malaysia) was invaded and fell early the following year. The invasion of Thailand lasted only a few hours before that country surrendered in December 1941. Other than Hawaii, Midway was the only target on Dec. 7 not to fall under Japanese control.
Those days were among the darkest of the Pacific war. Britain lost two huge battleships in a matter of minutesto aerial bombardment, and Winston Churchill wrote in his memoirs that their sinking was his lowest point of the entire war. The Japanese actions that day effectively crippled British naval strength in the Pacific.
3. The U.S. military responded quickly and decisively.
For months after Pearl Harbor, the United States suffered defeat after defeat in the Pacific theater. Rumors swept the country on Dec. 8 that the Navy was in pursuit of the attacking Japanese fleet, but these were false. Gen. Douglas MacArthur, in command of the Army garrison in the Philippines, sent Roosevelt a telegram pleading for naval assistance, including for U.S. subs to target the Japanese vessels delivering troops, but the requests went unanswered. There was little assistance to offer the beleaguered general, and the Philippines fell.