Russia and Japan have technically been at war with each other for almost 80 years. The US is the main roadblock to a peace treaty.
The agreement to give the Kuril Islands and the southern part of Sakhalin to the USSR was reached at the Yalta Conference attended by Joseph Stalin, Franklin Roosevelt, and Winston Churchill, in February 1945. The USSR, in its turn, pledged to join the war on the eastern front no later than two or three months after defeating Nazi Germany. The Southern Kurils were taken by Soviet forces in August-September 1945 and officially declared a part of the USSR a year later.
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