Task: Question Generation
Input (English): In Article 3 of the Treaty of San Francisco between the Allied Powers and Japan, which came into force in April 1952, the U.S. put the outlying islands of the Ryukyus, including the island of Okinawa—home to over 1 million Okinawans related to the Japanese—and the Bonin Islands, the Volcano Islands, and Iwo Jima into U.S. trusteeship. All these trusteeships were slowly returned to Japanese rule. Okinawa was returned on May 15, 1972, but the U.S. stations troops in the island's bases as a defense for Japan.
Output (English): When was Okinawa finally returned?