After the attack on Pearl Harbor on December 7, 1941, the United States Congress reacted swiftly and decisively. On December 8, 1941, the day after the attack, Congress convened and President Franklin D. Roosevelt delivered a speech requesting a declaration of war against Japan.
That same day, Congress passed the declaration of war with overwhelming support. The vote in the House of Representatives was 388 to 1 in favor, and the Senate passed the resolution unanimously, with one abstention. This marked the official entry of the United States into World War II.
In the following days, Congress also addressed other aspects of war mobilization, including defense spending, military conscription, and logistical support for the war effort. The attack on Pearl Harbor had united the American public and Congress in a determination to respond to the aggression of Japan, leading to a significant escalation of U.S. military involvement in the war.