Russia and Japan have a deeply contentious history, based mostly on territorial disputes . A chain of islands that runs between the Japanese mainland and Russia's Kamchatka Peninsula has been swapped back and forth over the past 128 years, since Tokyo and Moscow established diplomatic relations. In 1855, Sakhalin Island and the Kuril Islands were split between the two sides. The Treaty of St. Petersburg in 1875 gave Japan control of all of the Kuril Islands in exchange for control of Sakhalin, but after the Russo-Japanese war in 1904-1905, Japan took the southern half of Sakhalin Island. During World War II, the Soviets occupied the islands and at the Yalta Summit in 1945 were granted possession of them. The Japanese people on the islands were expelled in 1947 and sent back to Japan.