1855: Japan and Russia sign treaty establishing Japan-Russia boundary between islands of Etorofu and Uruppu (north of Etorofu).
1875: Russia yields 18 Kuril Islands to Japan for southern half of Sakhalin Island.
1904-5: Russo-Japanese War; Russia is defeated, cedes half of Sakhalin.
1918: 60,000 Japanese troops intervene in Far East against Bolshevik Revolution.
1925: Japan establishes diplomatic ties with Union of Soviet Socialist Republics.
1938-9: Soviet and Japanese troops fight along Manchurian and Mongolian borders.
April 1941: Five-year Soviet-Japan neutrality signed.
Aug. 8, 1945: Soviets join war against Japan, which ends Aug. 14. Soviets occupy Japanese part of Sakhalin and southern Kuril islands.
1952: Soviets decline to sign San Francisco Treaty, which formally ends Pacific War.
Oct. 19, 1956: Soviet-Japanese relations re-established. Soviets pledge to return two of four Kuril islands, but later repudiate pledge.
1973: Japanese premier visits USSR. Soviets agree to discuss ``unresolved'' issues from war.
Jan. 1986: Soviet foreign minister visits Japan. Two sides agree to talks on postwar treaty.
April 1991: Soviet leader to visit Japan for the first time.