Following the Mukden Incident in 1931 and the subsequent Japanese invasion of Manchuria, Inner Manchuria was proclaimed to be Manchukuo, a puppet state under the control of the Japanese army. The last Manchu emperor, Puyi, was then placed on the throne to lead a Japanese puppet government in the Wei Huang Gong, better known as "Puppet Emperor's Palace". Inner Manchuria was thus detached from China by Japan to create a buffer zone to defend Japan from Russia's Southing Strategy and, with Japanese investment and rich natural resources, became an industrial domination. Under Japanese control Manchuria was one of the most brutally run regions in the world, with a systematic campaign of terror and intimidation against the local Russian and Chinese populations including arrests, organised riots and other forms of subjugation. The Japanese also began a campaign of emigration to Manchukuo; the Japanese population there rose from 240,000 in 1931 to 837,000 in 1939 (the Japanese had a plan to bring in 5 million Japanese settlers into