Third and fourth terms of the presidency of Franklin D. Roosevelt well-defended island of Iwo Jima, taking control of that island the following month. On April 1, the U.S. landed on Okinawa Island, the largest of the Ryukyu Islands. The Japanese allowed the Americans to land on the island before launching a fierce attack that included "kamikaze" suicide attacks by Japanese aircraft. Japanese forces on Okinawa held out until June 1945; U.S. forces suffered over 60,000 casualties during the operation. In late 1943, Roosevelt, Churchill, and Stalin agreed to meet to discuss strategy and post-war plans at the Tehran Conference, which marked Roosevelt's first face-to-face meeting with Stalin. At the conference,
South Pacific Mandate detachments. In order to capture the islands from Japan, the United States military employed a "leapfrogging" strategy which involved conducting amphibious assaults on selected Japanese island fortresses, subjecting some to air attack only and entirely skipping over others. This strategy caused the Japanese Empire to lose control of its Pacific possessions between 1943 and 1945. The League of Nations mandate was formally revoked by the United Nations on 18 July 1947 pursuant to Security Council Resolution 21, making the United States responsible for administration of the islands under the terms of a United Nations trusteeship agreement which established the Trust