Okinawa, the southern-most prefecture of Japan, is an island chain; the main island is Okinawa island and the whole chain is more properly called the Ryukyu islands. Okinawa was a kingdom independent of Japan until the 1870s. During the Edo period, it was a tributary state of China, but also of Japan’s Satsuma domain, being too weak to resist the demands of either. Using this relationship as a pretext, the Japanese government gained full sovereignty over the Okinawan islands in the 1870s. Okinawa was occupied by the Americans from 1944 until 1970 when administration was returned to Japan. Okinawa is the poorest prefecture in Japan and the people feel that they are discriminated against.