he attack that took place on December 7, 1941, at Pearl Harbor on the island of Oahu, Hawaii, became the most shocking military defeat in U.S. history and plunged America into World War II. Japanese planes succeeded in damaging all eight battleships anchored in the harbor and caused over 3,000 American casualties. Japan severely incapacitated the U.S. Pacific fleet, but did not anticipate how Pearl Harbor would unite a previously divided America and commit a nation to war.