High Quality Content by WIKIPEDIA articles! On December 7, 1941, the Japanese launched a surprise attack on Pearl Harbor and hastened the entry of the United States into World War II on the side of the Allies. The day after the attack, President Franklin D. Roosevelt addressed a joint session of United States Congress. Roosevelt called December 7 "a date which will live in infamy". Congress declared war on the Empire of Japan amid outrage at the attack and the late delivery of the note from the Japanese government breaking off relations with the U.S. government, actions considered treacherous. Pacifist Congresswoman Jeannette Rankin, a Republican from Montana, cast the only dissenting vote.