Since the nineteenth century, both Japan and Russia have contested sovereignty over Sakhalin. The Japanese established settlements in southern Sakhalin in the late 1700s, and the Russians arrived in 1853. Two years later, when Japan and Russia opened diplomatic relations, they agreed that both nations might retain settlements on the island. In 1875, Japan abandoned its claims to Sakhalin because it had become difficult to oppose the Russians. Following Japan's defeat of Russia in the Russo-Japanese War of 1904–1905, however, Japan acquired full rights to southern Sakhalin and took the entire island after the 1917 Russian Revolution. Japan handed over to the Soviet Union control of Sakhalin north of the 50th Parallel as part of their normalization of diplomatic relations in 1925. Japan retained extensive rights to exploit oil, coal, timber, and other natural resources in the Soviet half of the island.
When the Soviet Union entered the war against Japan just days before the end of the Pacific conflict, the Red Army launched fierce attacks against the western coast of Sakhalin on 16 and 20 August 1945. Following conclusion of a local cease-fire on 23 August, the Soviets prohibited Japanese citizens on Sakhalin from leaving the island. Many were forced into hard labor on the island or in Siberia, and it was not until 1949 that they were all released.
As part of the price to get the Soviet Union into the war against Japan, at the February 1945 Yalta Conference the Western Allies had agreed to Soviet acquisition of all of Sakhalin. Although the 1951 San Francisco Peace Treaty with Japan confirmed the abandonment of Japanese claims on southern Sakhalin and the Kurile Islands, the transfer of those to the Soviet Union was not prescribed in the treaty. The Soviet Union, however, refused to sign the treaty. In October 1956, Japanese Prime Minister Hatoyama Ichirō visited Moscow and signed the Japan-Soviet Joint Declaration. This formally ended the state of war between the two nations but did not resolve the territorial dispute over the Kuriles and southern Sakhalin. The Soviet Union rejected the Japanese request to return to Japan the so-called Northern Territories of the Kuriles and Sakhalin, and the issue was put off.
The Soviets have held that Sakhalin Island is essential to securing their nation's southeastern flank, and this is the reason that they made such a desperate effort in August 1945 to take southern Sakhalin. The Sea of Okhotsk also became much more vital for military purposes following the development of submarine-launched ballistic missiles (SLBMs), and Soviet forces on Sakhalin were reinforced in the 1970s and 1980s. The Sea of Okhotsk was the most secure area for the Soviet nuclear missile submarine fleet, because all of the straits into the sea were under Soviet control. More generally, the Soviets felt less secure during this period because of ongoing tensions with China and strengthened security cooperation between the United States and Japan. For many years, the Japanese government feared that Soviet forces might invade northern Hokkaido Island on the Soya Straits to complete their enclosure of the Sea of Okhotsk. During the Cold War, Japan invested heavily in defenses on northern Hokkaido, which lay only a few miles south of Sakhalin.
In September 1983, Soviet aircraft shot down Korean Airlines (KAL) Flight 007 near Sakhalin. Currently, the issue of Sakhalin and the Kuriles remains a stumbling block to smoother relations between Japan and Russia.
Stephan, John J. Sakhalin: A History. New York: Clarendon, 1971.; U.S. Department of Defense. Sea of Okhotsk, Soviet Union, Ostrov Sakhalin including the Tatar Strait. Washington, DC: DMA/Combat Support Center/DOA, 1994.