were a Japanese clan claiming descent from Taira no Tomomori. The clan governed and held Tsushima Island from the 13th through the late 19th century, from the Kamakura period until the end of the Edo period and the Meiji Restoration. In 1587, Toyotomi Hideyoshi confirmed the clan's possession of Tsushima. In the struggles which followed Hideyoshi's death, the clan sided with the Tokugawa; however, they did not participate in the decisive battles which preceded the establishment of the Tokugawa shogunate. The descendants of tozama Sō Yoshitoshi (1568–1615) remained at Tsushima-Fuchū Domain (100,000 koku) in Tsushima Province until the abolition of the han system. The head of this clan line was ennobled as count in 1884. History Historians consider the Sō clan to have been an offshoot of the Koremune clan (惟宗氏), who served as local officials of Dazaifu and Tsushima Province. The earliest evidence of Sō clan cohesion arises in the 11th century. The Koremune had their start as governors of Tsushima following an incident in 1246, when the Abiru clan, local district officials (zaichōkanjin) on Tsushima, rebelled against the Chinzei Bugyō and the Dazaifu government which governed all of Kyūshū and the surrounding regions on behalf of the Kamakura shogunate. Dazaifu ordered Koremune Shigehisa to stop the rebellion and to destroy the Abiru clan. He was rewarded for his victory with the post of Jito (local land steward), by the Shōni clan, shugo (governors) of Tsushima. The Koremune extended its influence on Tsushima over the course of the Kamakura period, as the deputies of the Shōni. When the Mongols invaded Japan in 1274, clan head Sō Sukekuni fought against the invaders and died on Tsushima. The Sō clan fought for the Shōni clan and for the Ashikaga Northern Court during the Nanboku-chō period (1336–1392), and seized a portion of Chikuzen Province. Imagawa Ryōshun became Chinzei Tandai (head of the Dazaifu government) soon afterwards, and the Imagawa clan became shugo of Tsushima. When Imagawa Ryōshun was dismissed from his post in 1395, Sō Sumishige became shugo of Tsushima. Though now holding the hereditary post of shugo of Tsushima, the clan remained vassals of the Shōni until the late 15th century. In the course of breaking away from the Shōni clan, the Sō clan started to claim that it originated with a grandson of Taira no Tomomori, Taira no Tomomune. The Sō clan moved its base from northern Kyūshū to Tsushima