The occupation of Outer Mongolia by the Beiyang government of the Republic of China after the revocation of Outer Mongolian autonomy began in October 1919 and lasted until 18 March 1921, when Chinese troops in Urga were routed by Baron Roman von Ungern-Sternberg's White Russian and Mongolian forces. These, in turn, were defeated by the Red Army and its Mongolian allies by June 1921.

The Mongolian People's Party (MPP) is a social democratic political party in Mongolia. It was founded as a communist party in 1920 by Mongolian revolutionaries and is the oldest political party in Mongolia. The party played an important role in the Mongolian Revolution of 1921, which was inspired by the Bolsheviks' October Revolution. Following independence, it governed Mongolia as a one-party socialist state. The party changed its name to the Mongolian People's Revolutionary Party (MPRP) and joined the Communist International in 1924 and served as a sole-ruling party of the Mongolian People's Republic.