The war started for America on 7 December 1941 with the Japanese attack on Pearl Harbor, and the invasion of the Philippines and the Dutch East Indies. Hard-fought campaigns in Papua and Guadalcanal followed in 1942. In 1943, the Japanese were driven from the Aleutian Islands, and U.S. forces landed in the northern Solomon Islands, the Gilbert Islands, and the Bismarck Archipelago. This was followed in 1944 by the invasion of the Marshall Islands, a series of landings in western New Guinea, the capture of the Mariana Islands and Battle of Palau. The U.S. Army returned to the Philippines in October 1944, waging major campaigns on Luzon and the southern Philippines through 1945. U.S. forces landed on Okinawa and in April 1945. Atomic bombs developed under the direction of the U.S. Army were dropped on Hiroshima and Nagasaki in 1945, which caused the Japanese to unconditionally surrender on 2 September 1945, aboard the USS "Missouri".