Over the course of Japan's Edo period, the Okinawan Kingdom of Ry贖ky贖 sent eighteen missions to Edo, the capital of Tokugawa Japan. The unique pattern of these diplomatic exchanges evolved from models established by the Chinese, but without denoting any predetermined relationship to China or to the Chinese world order. The Kingdom became a vassal to the Japanese feudal domain of Satsuma following Satsuma's 1609 invasion of Ry贖ky贖, and as such were expected to pay tribute to the shogunate