After Japan's attack on American military installations in Hawaii and a series of victories in late 1941 and early 1942, Japan controlled huge portions of Asia and the Pacific by the summer of 1942. The United States benefited from the survival of the Pacific Fleet's submarines and aircraft carriers, and by the middle of 1942 American forces had stopped Japanese expansion in the Battles of Coral Sea, Midway, and Guadalcanal. The United States adopted a strategy of island hopping to avoid enemy strongholds, though not all could be bypassed. Before the war ended, American armed forces fought at least twenty-one major campaigns, engaged in over thirty-six battles, and carried out countless sea-to-land assaults. As the Allies moved closer to the Japanese homeland, the landings grew bloodier, and the atomic bombings on August 6th and 9th led to Japan's surrender and the end of World War II on 2 September 1945.