The event that shook the United States from its non interventionist foreign policy and directly involved it in World War II was the Japanese bombing of the U.S. naval base at Pearl Harbor. Japanese bombers struck Pearl Harbor; a U.S. naval base in Hawaii. Around 2,500 Americans were killed. This direct and deliberate strike against U.S. soil and U.S. citizens shocked the public. This event now necessitated the U.S. to enter the war to defeat the aggressors.