The Ryukyu Kingdom (present-day Okinawa) was located at the intersection of the South China Sea and East China Sea facing South China and Kyushu. Long before the Ryukyu Kingdom period (1429–1879), it was already alert to the advantages and opportunities offered by the sea and put them to use in its trade with East and Southeast Asia. Under the Ryukyu Kingdom, missions were sent to Southeast Asia to obtain goods for its tributary trade with China. Even after the invasion by the Satsuma domain of Japan in 1609, Ryukyu continued to dispatch tribute envoys to Qing China. At the same time, it sent envoys to the Tokugawa shoguns in Edo (present-day Tokyo) and maintained relations with Korea. The period from the late fourteenth century to the early sixteenth century was one of the most prosperous in the history of the Ryukyu Kingdom. This prosperity was due in large measure to the far-flung trading activities of its people, who traversed the East and Southeast Asian waters as enterprising agents of entrepot trade for countries bordering those waters. Not only were the Ryukyuans in contact with China and Japan, but relations were also established and maintained with Korea and Southeast Asian countries.