The Pacific War was a major conflict during World War II that took place between 1941 and 1945. It primarily involved the forces of the United States and its allies fighting against the Empire of Japan. The war began after Japan's surprise attack on Pearl Harbor in December 1941, leading to the U.S. entering the war. The conflict included significant battles such as the Battle of Midway and the Battle of Iwo Jima. It ended with Japan's surrender following the dropping of atomic bombs on the cities of Hiroshima and Nagasaki in August 1945, marking a pivotal moment in world history.