The Inner Mongolian Campaign in the period from 1933 to 1936 were part of the ongoing invasion of northern China by the Empire of Japan prior to the official start of hostilities in the Second Sino-Japanese War. In 1931, the invasion of Manchuria secured the creation of the puppet state of Manchukuo and in 1933, Operation Nekka detached the province of Rehe from the Republic of China. Blocked from further advance south by the Tanggu Truce, the Imperial Japanese Army turned its attention west, towards the Inner Mongolian provinces of Chahar and Suiyuan, with the goal of establishing a northern China buffer state. In order to avoid overt violation of the Truce, the Japanese government used proxy armies in these campaigns while Chinese resistance was at first only provided by Anti-Japanese resistance movement forces in Chahar. The former included in the Inner Mongolian Army, the Manchukuo Imperial Army, and the Grand Han Righteous Army. Chinese government forces were overtly hostile to the anti-Japanese resistance and resisted Japanese aggression only in Suiyuan in 1936.