http://en.wikipedia.org/wiki/Volcano_and_Ryukyu_Islands_campaign
The Volcano and Ryūkyū Islands campaign was a series of battles and engagements between Allied forces and Imperial Japanese forces in the Pacific Ocean campaign of World War II between January and June, 1945.
The campaign took place in the Volcano and Ryukyu island groups. The two main land battles in the campaign were the Battle of Iwo Jima (February 16-March 26, 1945) and the Battle of Okinawa (April 1-June 21, 1945). One major naval battle occurred, called Operation Ten-Go (April 7, 1945) after the operational title given to it by the Japanese.
The campaign was part of the Allied Japan campaign intended to provide staging areas for an invasion of Japan as well as supporting aerial bombardment and a naval blockade of the Japanese mainland. The dropping of atomic weapons on two Japanese cities and the hammer-blow Soviet invasion of Japanese Manchuria, however, caused the Japanese government to surrender without an armed invasion being necessary.