On what date did the Soviet Union invade Japanese-held Manchuria in 1945?

The Soviet Union invaded Japanese-held Manchuria on 9 August 1945. The operation, known as the Soviet invasion of Manchuria or the Manchurian Strategic Offensive Operation, began shortly after the Soviet declaration of war against Japan.

Soviet forces attacked the Japanese-controlled state of Manchukuo from several directions. The Red Army’s large, mechanized offensive rapidly overwhelmed the Kwantung Army, Japan’s major force in Manchuria. Soviet troops also advanced into areas including Inner Mongolia, southern Sakhalin, and northern Korea.

The invasion followed agreements made at the Tehran and Yalta conferences, under which the Soviet Union promised to enter the war against Japan after Germany’s defeat. It began between the atomic bombings of Hiroshima and Nagasaki, making 9 August one of the most consequential dates of the war’s final phase.

Historians continue to debate the relative importance of the atomic bombings and Soviet entry in Japan’s decision to surrender. Both developments sharply narrowed Japan’s military and diplomatic options before the August announcement.