Russian colonization of the area began in the late 16th cent., when Cossacks built forts and settlements; Russian fur traders arrived soon afterward. In 1856–57 the Russians took advantage of a weak Chinese empire to occupy all of the territory N of the Amur, and in 1860 they seized the land E of the Ussuri; the People's Republic of China has denounced the "unequal treaties" by which Russia sought to legitimize these conquests. In 1875 the Russians took Sakhalin (formerly under joint Russo-Japanese control) from Japan. With completion of the Trans-Siberian RR, Russian settlement of the area accelerated. Russia retained N Sakhalin under the Treaty of Portsmouth (1905), but Japan was awarded the rest of the island.
After the Russian Revolution (1917), Japanese forces landed at Vladivostok and occupied large parts of the Russian territory. They were joined by a U.S., British, and French expeditionary force, which arrived in the apparent hope of preventing the Germans from using the area's resources during World War I. The interventionist forces gave considerable support to the anti-Bolshevik units of Admiral Kolchak, which had occupied most of the region. By 1920, Bolshevik units had defeated Kolchak's troops, and the Allies withdrew. However, the Japanese remained, and in 1920 the Far Eastern Republic was formed as a buffer state between Japan and the Soviet Union. In 1922, the Japanese forces withdrew, the republic was dissolved, and the area was incorporated into the USSR as a region.
From 1926 to 1938 the whole area was called the Far Eastern Territory; it was then renamed the Soviet Far East. In the settlement following World War II, the USSR acquired the southern half of Sakhalin and the Kuril Islands. The Japanese, however, subsequently disputed Soviet rights to the southern four islands in the Kuril chain. In 1969, Sino-Soviet clashes erupted along the Amur and Ussuri frontiers. Negotiations bogged down, and both sides reinforced their forces along the long border.
Glasnost and perestroika brought an opening of the Soviet Far East: Vladivostok was allowed to accept foreign ships, and air flights began between Alaska and various cities. The dissolution of the USSR brought renewed struggle for autonomy, particularly among the Yakut and Chukchi peoples, and the area also lost population due to Russian outmigration. The disagreement over the fate of the Kuriles prevented Japanese investment in the region, and in the 1990s there was friction between local officials and foreign investors. Since the late 1990s, however, trade with China and Chinese investment in the region, mainly in the south, has become increasingly important.