What Soviet campaign against Japanese forces began on 9 August 1945 and helped pressure Japan to surrender?

The Soviet invasion of Manchuria began on 9 August 1945 and helped pressure Japan to surrender.

The campaign, also called the Manchurian Strategic Offensive Operation or Operation August Storm, sent Soviet forces into Japanese-occupied Manchuria and the puppet states of Manchukuo and Mengjiang. Soviet forces attacked on multiple fronts and rapidly overwhelmed the Kwantung Army.

The offensive began between the atomic bombings of Hiroshima on 6 August and Nagasaki on 9 August. The Soviet Union had promised at the Yalta Conference to enter the war against Japan within three months of Germany’s defeat, and it declared war on Japan on 8 August, with combat beginning the next day.

Historians debate the relative weight of the atomic bombings and the Soviet entry in Japan’s decision to surrender. Both developments changed Japan’s strategic situation dramatically. The campaign continued until 2 September 1945, the date of Japan’s formal surrender.