The Japanese puppet state in Manchuria was called Manchukuo.
Japan established Manchukuo in 1932 after the Japanese occupation of Manchuria. The state was formally presented as an independent empire, but Japanese authorities controlled its administration, military affairs, and major economic activity. The former Qing emperor Puyi became its nominal ruler, later using the imperial title Kangde.
When the Soviet Union entered the war against Japan in August 1945, Soviet forces invaded Manchukuo as part of the Soviet invasion of Manchuria. The Kwantung Army, Japan’s major force in the region, was rapidly defeated. Manchukuo’s government collapsed, and Puyi later renounced the throne.
Manchukuo is often confused with Mengjiang, another Japanese-backed regime located mainly in Inner Mongolia. They were separate political entities. Manchuria itself is the geographic region, while Manchukuo was the Japanese-sponsored state created there. Soviet occupation and the movement of Chinese Communist forces into the region later influenced the Chinese Civil War.