Since the Russo-Japanese War of 1905, Japan had maintained a military presence in Manchuria. In 18 September 1931, the Mukden Incident occurred. There was a small explosion on the tracks of a Japanese railway, north of Mukden. Japan invaded Manchuria in the aftermath. The Japanese army mobilized the Kwantung Army and attacked Chinese troops. The Minseito government, headed by Hamaguchi's successor Wakatsuki Reijirō, was unable to curb the army's offensive. The Kwantung Army conquered all of Manchuria and set up the puppet state of Manchukuo on 1 March 1932. The last Emperor of China, Puyi, was installed as the puppet ruler of Manchukuo. The Diet, now dominated by army officials, voted to withdraw from the League of Nations. The first seeds of the coming conflict had been sown.