The Japanese launched a surprise attack on the U.S. naval base at Pearl Harbor on December 7, 1941, sinking or damaging numerous American battleships and warships and killing over 2,300 American service members and civilians. The attack, which lasted only 90 minutes, was a preventative strike planned by Admiral Yamamoto to neutralize the U.S. Pacific fleet and discourage America from interfering with Japanese expansion in Asia. Though devastating in the short term, key facilities at Pearl Harbor survived and the attack had the opposite effect by galvanizing American support for entering World War II against Japan and Germany.