What event precipitated the U.S. entry into World War II?

The attack on Pearl Harbor on December 7, 1941, was the pivotal event that led to the United States' entry into World War II. Prior to this attack, the U.S. had maintained a position of neutrality, although it was providing support to the Allies through programs such as Lend-Lease and facing increasing pressures to formally engage in the conflict. The surprise military strike by the Imperial Japanese Navy against the U.S. naval base at Pearl Harbor resulted in significant loss of life and damage to the U.S. Pacific Fleet. In response to this attack, President Franklin D. Roosevelt addressed Congress, leading to an official declaration of war against Japan on December 8, 1941. This event marked a dramatic shift in U.S. foreign policy and was a key turning point that rallied public support for entering the war.

In contrast, the invasion of France in 1940 was a significant event in the early years of the war, but it did not directly compel the U.S. to join the conflict at that time. The sinking of the Lusitania occurred during World War I and was another critical moment in U.S. history, but it did not lead to war in World War II. Similarly, the Battle of Britain