The Kuril Islandsor Chishima Islands (Japanese:千島列島, Chishima-rettō, Russian:Курильские острова) is an archipelago of 56 islands stretching 810 miles from Hokkaido(Matsumae Island), Japan to Kamchatka, Russia, separating the Sea of Okhotsk from the northern Pacific Ocean. The islands were originally inhabited by Ainu people, and the Matsumae clan laid claim to the islands during the era of the Tokugawa Shogunate. In 1812, the Tokugawa Shogunate and the Russian Empire negotiated a border treaty, resolving the first of many territorial disputes concerning the Kuriles. In 1875, Japan ceded Sakhalin(Karafuto) to Russia in exchange for complete control over the Kuriles, and the Kuriles served as a military base for the Japanese; from 1918 to 1925, Japanese troops from the northern Kuriles occupied Kamchatka during Japan's intervention in the Russian Civil War. The islands, along with South Sakhalin (Minami-Karafuto), were invaded by the Soviet Union under Stalin, and the local Japanese residents (Yamato and Ainu tribes) were expelled or killed. in 1945 at the end of World War II. In 2013, the Kuriles had a population of 19,434 people, with many of them being Russians, Ukrainians, Belarusians, Tatars, Nivkhs, Oroch, and Ainus; Orthodox Christianity and Islam were the only two major religions in the islands.