The Soviet invasion of Manchuria began on August 9, 1945, during the final week of the Pacific War.
The operation, also known as the Manchurian Strategic Offensive Operation or Operation August Storm, began when Soviet forces attacked Japanese-held Manchuria and the Japanese puppet state of Manchukuo. Soviet troops also moved into Inner Mongolia and northern Korea during the campaign.
The invasion came three days after the atomic bombing of Hiroshima and hours before the atomic bombing of Nagasaki. Japan had hoped the Soviet Union might mediate with the Western Allies, but the Soviet declaration of war destroyed that diplomatic expectation.
Historians continue to debate the relative importance of the atomic bombings and Soviet entry in Japan's decision to surrender. Both developments sharply changed Japan's strategic situation. The Kwantung Army formally surrendered on August 16, although fighting continued in some areas until the September 2 surrender ceremony.