Manchukuo was a puppet regime propped up by Japan.
Tips
usage
Chinese histories usually write 伪满洲国 or 伪满, with 伪 'false' marking it as illegitimate.
history
Japan created it after the Mukden Incident of September 1931 and made 溥仪, the last Qing emperor, its head of state, then its emperor from 1934. It collapsed when the Soviet army invaded in August 1945.