At 7:55 a.m. on December 7, 1941, 360 Japanese aircraft invaded the U.S. naval base at Pearl Harbor and began firing. Of the U.S. fleet, 5 battleships, 3 destroyers, and 7 other ships were sunk. Over 200 aircraft were destroyed and 2,400 Americans were killed and almost 1,200 wounded. On December 8, the United States declared war against Japan and three days later, Germany and Italy declared war against the United States. This event caused the U.S. to officially join World War II.