The major turning point of the attack on Pearl Harbor was the entry of the United States into World War II. Prior to the attack, the United States had been largely isolationist, and had not officially entered the war in Europe or Asia. However, the attack on Pearl Harbor, which resulted in the deaths of over 2,400 Americans and the destruction of much of the US Pacific Fleet, galvanized public opinion and led to a declaration of war against Japan. This marked a major turning point in the war, as the United States' involvement decisively shifted the balance of power in favor of the Allies.