The Ryukyu Islands are a chain of islands located on the eastern limit of the East China Sea and to the southwest of the island of Kyushu in Japan. Okinawa Island is the largest island in the chain. The Ryukyu Kingdom was annexed by the Empire of Japan in 1872, although the kingdom had been part of the feudal Satsuma Domain in Kyushu since 1609. During World War II, the islands came under the occupation of the United States military in 1945, and a civilian government was set up under American control in 1952. The islands reverted to the control of Japan in 1972. The first definitive stamps of the Ryukyu Islands were issued on July 1, 1948, and the first commemorative stamps were issued on February 12, 1951. The final Ryukyu Island stamp was a commemorative stamp issued on April 20, 1972, after which time stamps of Japan were valid.