Taishō period Shōwa period The Suiyuan campaign (Chinese: 綏遠抗戰; pinyin: Suīyuǎn kàngzhàn; Japanese: 綏遠事件, romanized: Suien jiken) was an attempt by the Inner Mongolian Army and Grand Han Righteous Army, two forces founded and supported by Imperial Japan, to take control of the Suiyuan province from the Republic of China.

The defense of Suiyuan, one of the first major successes of China's National Revolutionary Army over Japanese-supported forces, greatly improved Chinese morale.

In September 1931, the Mukden Incident resulted in the Japanese Kwantung Army completely occupying the three northeastern provinces of China and defeating the forces of the pro-Nationalist warlord who had ruled the region, the "Young Marshal" Zhang Xueliang.

In 1929, they made contact with Prince Demchugdongrub (De Wang), an Inner Mongolian nobleman and nationalist leader who wanted more autonomy from the Kuomintang government in Nanjing.

The Japanese took advantage of the disputes for increased autonomy between the Mongolians and the Nanjing government to bring Prince De Wang to their side with promises of providing weapons and helping him take over Inner Mongolia.

The new government adopted the birthday of Genghis Khan as its calendar, and Prince De swore "to recover the original land of the Mongols, and to complete the great mission of national revival.

[9] The Chinese National Revolutionary Army garrison in the Suiyuan province was reinforced by troops sent from Nanjing by the Kuomintang government, including an elite anti-aircraft battalion.

[2][3] Although that marked the end of the Mongolian Army's invasion, small-scale fighting continued in Suiyuan over the next several months until the beginning of open hostilities resulting from the Marco Polo Bridge Incident of July 1937.

"[3] The Xi'an Incident, which resulted in the Kuomintang (the Nationalists) and the Chinese Communist Party recognizing the greater threat of Japan and agreeing to work together to fight the Japanese, was thought to be partly influenced by the events of the Suiyuan campaign.

[10] Following his defeat there, Prince Demchugdongrub and his Inner Mongolian troops retreated to northern Chahar, where he was forced to rebuild his army due to the considerable losses it had sustained.

[3] However, small-scale combat still continued in the Suiyuan province until the beginning of open hostilities as a result of the Marco Polo Bridge Incident the following year.

[12] Prince De's Inner Mongolian army was rebuilt with Japanese assistance and by the time war broke out in July 1937, his force consisted of 20,000 men in eight cavalry divisions.

These troops participated in Operation Chahar and the Battle of Taiyuan during which Japanese regular and allied Inner Mongol forces finally captured eastern Suiyuan province.