The Yalta Conference, also known as the Crimea Conference, held 4–11 February 1945, was the World War II meeting of the heads of government of the United States, the United Kingdom and the Soviet Union to discuss the postwar reorganization of Germany and Europe.
Each of the three leaders had his own agenda for postwar Germany and liberated Europe. Roosevelt wanted Soviet support in the Pacific War against Japan, specifically for the planned invasion of Japan (Operation August Storm), as well as Soviet participation in the United Nations.
One Soviet precondition for a declaration of war against Japan was an American official recognition of the Mongolian independence from China (the Mongolian People’s Republic had been a Soviet satellite state from 1924 to World War II). The Soviets also wanted the recognition of Soviet interests in the Chinese Eastern Railway and Port Arthur but not asking the Chinese to lease. Those conditions were agreed to without Chinese participation.
The Soviets also wanted the return of South Sakhalin, which had been taken from Russia by Japan in the Russo-Japanese War in 1905, and the cession of Kuril Islands by Japan.
The Yalta Agreement, signed by the US, Great Britain and the Soviet Union, stated:
The leaders of the three great powers – the Soviet Union, the United States of America and Great Britain – have agreed that in two or three months after Germany has surrendered and the war in Europe is terminated, the Soviet Union shall enter into war against Japan on the side of the Allies on condition that: … 2. The former rights of Russia violated by the treacherous attack of Japan in 1904 shall be restored, viz.: (a) The southern part of Sakhalin as well as the islands adjacent to it shall be returned to the Soviet Union; … 3. The Kuril islands shall be handed over to the Soviet Union.
Japan and the US claimed that the Yalta agreement did not apply to the Northern Territories because they were not a part of the Kuril Islands, although US geographers have traditionally listed them as part of the Kuril chain. In a 1998 article in the journal Pacific Affairs, Bruce Elleman, Michael Nichols and Matthew Ouimet argue that the US never accepted the cession of all the Kuril Islands to the Soviet Union and has maintained from Yalta onward that it simply agreed at Yalta that Moscow could negotiate directly with Tokyo to come to a mutually acceptable solution, and that the US would support in such a peace agreement the Soviet acquisition of the Kurils. As a key piece of evidence, the same article quotes an August 27, 1945, letter from U.S. President Harry Truman to Soviet Premier Joseph Stalin: “You evidently misunderstood my message [about the Kuril Islands] … I was not speaking of any territory of the Soviet Republic. I was speaking of the Kurile Islands, Japanese territory, disposition of which must be made at a peace settlement. I was advised that my predecessor agreed to support in the peace settlement the Soviet acquisition of those islands.” The Soviet Union—and subsequently, Russia—rejected this position.
The Yalta Agreement, which the Soviet Union used as the strongest evidence for claiming the Northern Territories, was a secret agreement among three countries: the US, the UK and the Soviet Union. Therefore, Japan should not be bound by that agreement. The US government, a party concerned, officially stated that the agreement has no legal effect on territorial transfer.