World War II began for the United States on December 7, 1941, with the Japanese attack on Pearl Harbor. This attack prompted a dramatic shift in U.S. foreign policy, as the nation had previously maintained a stance of neutrality while supporting allies through measures like the Lend-Lease Act. Following the attack, President Franklin D. Roosevelt addressed Congress, declaring war on Japan on December 8, 1941. This declaration marked America's full entry into the global conflict, subsequently followed by Germany and Italy declaring war on the U.S. shortly thereafter, cementing the country's role in the fight against the Axis powers throughout the war.