Which Soviet military operation began on August 9, 1945, during the final campaign against Japan?

The Soviet invasion of Manchuria began on August 9, 1945, during the final campaign against Japan.

The operation attacked Japanese-occupied Manchuria and the Japanese puppet state of Manchukuo. Soviet forces advanced from several directions, using a large-scale pincer movement across difficult deserts, mountains, and fortified areas. The campaign is also known as the Manchurian Strategic Offensive Operation and, in some Western accounts, Operation August Storm.

The Soviet Union declared war on Japan on August 8 Moscow time, and the invasion began shortly afterward. Its timing shocked Japanese leaders, who had hoped the Soviet Union might help negotiate with the Western Allies.

The rapid collapse of the Kwantung Army added to the pressure created by the atomic bombings of Hiroshima and Nagasaki. Japan announced acceptance of the Potsdam Declaration on August 15, although fighting continued in some regions afterward.