On 9 August 1945, the Soviet Union invaded the Japanese puppet state of Manchukuo. It was the last campaign of the Second World War, and the largest of the 1945 Soviet–Japanese War, which resumed hostilities between the Union of Soviet Socialist Republics and the Empire of Japan after almost six years of peace. Soviet gains on the continent were Manchukuo, Mengjiang (Inner Mongolia) and northern Korea. The Soviet entry into the war and the defeat of the Kwantung Army was a significant factor in the Japanese government's decision to surrender unconditionally, as it made apparent the Soviet Union had no intention of acting as a third party in negotiating an end to hostilities on conditional terms.