Which 1945 campaign began when the Soviet Union invaded Japanese-held Manchuria?

The Soviet invasion of Manchuria began on August 9, 1945, against Japanese-held Manchuria.

The Red Army attacked Japanese forces shortly after the Soviet Union declared war on Japan. Soviet forces advanced from several directions against the Kwantung Army, which defended the Japanese puppet state of Manchukuo. The campaign also affected Inner Mongolia, northern Korea, southern Sakhalin, and the Kuril Islands.

The invasion was a major factor in Japan’s decision to surrender, alongside the atomic bombings of Hiroshima and Nagasaki. Japanese leaders had hoped the Soviet Union might mediate a conditional peace, but Soviet entry destroyed that diplomatic hope. The Kwantung Army officially surrendered on August 16, although fighting continued in some areas until the formal surrender on September 2.