The Japanese assassinated him on 2 June 1928, in what is known as the Huanggutun Incident.[83] Following the Mukden Incident in 1931 and the subsequent Japanese invasion of Manchuria, the Japanese declared Inner Manchuria an "independent state", and appointed the deposed Qing emperor Puyi as puppet emperor of Manchukuo. 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.[84] Manchukuo was used by Japan as a base to invade the rest of China.