The Soviet Union began its invasion of Japanese-held Manchuria on 9 August 1945, opening the Soviet–Japanese War.
The Soviet declaration of war was delivered by Foreign Minister Vyacheslav Molotov to Japan’s ambassador in Moscow on 8 August, with the Soviet government stating that it would be at war from 9 August. Soviet forces then attacked Japanese positions across Manchuria shortly after midnight in Trans-Baikal time.
The offensive followed agreements made at the Yalta Conference, where Joseph Stalin had promised to enter the war against Japan after Germany’s defeat. It also violated the Soviet–Japanese Neutrality Pact, which the Soviet Union had announced it would not renew in April 1945.
The invasion struck the Kwantung Army and rapidly overwhelmed Japanese defenses in Manchuria, northern Korea, southern Sakhalin, and the Kuril Islands. Japan’s leaders faced this Soviet attack between the atomic bombings of Hiroshima and Nagasaki. The declaration is often dated 8 August, while the invasion and state of war began on 9 August in the Far East.