What event led the U.S. to enter World War II?

The attack on Pearl Harbor on December 7, 1941, was the pivotal event that led the United States to enter World War II. This surprise military strike by the Japanese Imperial Navy aimed specifically at the U.S. naval base at Pearl Harbor, Hawaii, resulted in significant loss of life and damage to the Pacific Fleet. In the aftermath of the attack, which destroyed numerous ships and aircraft, killed over 2,400 Americans, and wounded almost 1,200 others, the U.S. government and public were galvanized to take action.

Prior to this attack, the United States had been largely isolationist, focusing on domestic issues and avoiding direct involvement in the global conflict. The attack not only united the American populace in support of war but also directly led to President Franklin D. Roosevelt asking Congress for a declaration of war against Japan, which was granted on December 8, 1941. This marked the formal entry of the U.S. into World War II, leading to significant military engagement in both the Pacific and European theaters.

The other options, while important events in the context of the war, did not directly trigger U.S. involvement. The bombing of Hiroshima occurred later in the war, the invasion of Poland marked the beginning of