The global event that the attack on Pearl Harbor prompted the United States to join was World War II. The surprise military strike by the Japanese Navy on December 7, 1941, targeted the U.S. naval base in Hawaii and led to significant losses, including the sinking of battleships and thousands of deaths. In response, the United States declared war on Japan the following day, marking its official entry into the conflict. The attack galvanized American public opinion, unifying the nation in support of the war effort. Consequently, the U.S. increased military production and mobilized forces, playing a critical role in the eventual Allied victory.