On this day in 1941, more than 2,400 Americans were killed in a surprise military attack on the United States맥스카지노� naval base at Pearl Harbor in Hawaii.The attack was carried out by the Japanese Navy Air Service and struck a critical blow against the U.S. Pacific Fleet.President Franklin D. Roosevelt and his advisers knew a Japanese attack on the U.S. was probable after diplomatic negotiations between the two countries broke down.However, nothing had been done to increase security at Pearl Harbor leading up to the attack.The attack was carried out at 7:55 a.m. Hawaii time by more than 350 Japanese warplanes. For more, watch the video above.