On December 7, 1941, the U.S. naval base in Pearl Harbor was attacked in one of the biggest military surprises in the history of warfare. In less than two hours:
The American people were outraged. Though diplomatic relations between the United States and Japan were deteriorating, they had not yet broken off at the time of the attack. Instantly, the incident united the American people in a massive mobilization for war and strengthened American resolve to guard against any future lapse of military alertness.