Political map of East Asia and the Western Pacific 25 June 1921 (Russia in Mongolia): Ungern von Sternberg (Ungern von Sternberg), a Russian general fleeing the Soviet advance (Russian Civil War), took advantage of Chinese weakness (Warlord era) to occupy Mongolia. His rule would only last a few months before Soviet and Mongolian forces expelled him (Outer Mongolian Revolution of 1921), however the Soviet dominance which followed (Mongolian People's Republic) would last for 70 years.