The Inner Mongolian Army was first formed by Prince Demchugdongrub with his personal bodyguard of 900 men in 1929. Although only armed with rifles and a couple of field guns from the Mukden arsenal, a gift of the Young Marshal (Zhang Xueliang) in 1929. His force became very efficient with the assistance of advisors from the Japanese Army. It was later expanded to 9 Divisions (8 of Cavalry) with 10,000 men for the Suiyuan Campaign of 1936 with the addition of Manchukuoan Mongol irregulars from Jehol under Li Shou-hsin, and various Mongol irregular troops from Chahar, and Suiyuan, bandits and Chinese deserters. Wang Ying lead a force of 6,000 Chinese troops in four brigades called the Grand Han Righteous Army.
After the defeat in the Suiyuan Campaign in 1936 the army was reformed into eight small Cavalry Divisions with a total force of about 20,000 men. It participated with the Japanese Army in the conquest of Suiyuan in 1937. Elements were also involved in the battle of Taiyuan.