The Attack on Pearl Harbor: Japan's astonishing plot to ambush the United States, the spark that ignited the Pacific War. On the quiet morning of December 7, 1941, Japanese naval aircraft launched a devastating bombardment of Pearl Harbor in Hawaii. This unannounced surprise attack destroyed most of the combat strength of the U.S. Pacific Fleet, killing more than 2,400 Americans and injuring over 1,000. The attack shocked the world and changed the course of history. The next day, President Roosevelt delivered his famous “Day of Infamy” speech to Congress and declared war on Japan, officially entering World War II. The conflict lasted more than four years and was one of the bloodiest wars in human history.