The Tsardom of Russia, Russian Empire, Soviet Union, capitalist and communist China performed many genocide actions against the Mongols (assimilate, reduce the population, extinguish the language, culture, tradition, history, religion and ethnic identity). During Imperial Russia, Tsar Peter the Great said: "The headwaters of the Yenisei River must be Russian land". Russian Empire sent the Kalmyks and Buryats to war to reduce the populations (World War I and other wars).
Soviet Russian scientists attempted to convince the Kalmyks and Buryats that they were not Mongols during the 20th century (demongolization policy). 35,000 Buryats were killed during the rebellion of 1927 and around one-third of Buryat population in Russia died in the 1900s–1950s. In 1919 the Buryats established a small theocratic Balagad state in Kizhinginsky District of Russia and the Buryat's state fell in 1926. In 1958, the name "Mongol" was removed from the name of the Buryat-Mongol Autonomous Soviet Socialist Republic.
On 22 January 1922 Mongolia proposed to migrate the Kalmyks during the Kalmykian Famine but Russia refused. 71–72,000 (93,000?; around half of the population) Kalmyks died during the famine. The Kalmyks revolted against Russia in 1926, 1930 and 1942–1943. In 1913, Nicholas II, king of Russia, said : "We need to prevent from Volga Tatars. But the Kalmyks are more dangerous than them because they are the Mongols so send them to war to reduce the population".
 On 23 April 1923 Joseph Stalin, communist leader of Russia, said: "We are carrying out wrong policy on the Kalmyks who related to the Mongols.Our policy is too peaceful". In March 1927, Soviet deported 20,000 Kalmyks to Siberia, tundra and Karelia.The Kalmyks founded sovereign Republic of Oirat-Kalmyk on 22 March 1930. The Oirat's state had a small army and 200 Kalmyk soldiers defeated 1,700 Soviet soldiers in Durvud province of Kalmykia but the Oirat's state destroyed by the Soviet Army in 1930. Kalmykian nationalists and Pan-Mongolists attempted to migrate Kalmyks to Mongolia in the 1920s.Mongolia suggested to migrate the Soviet Union's Mongols to Mongolia in the 1920s but Russia refused the suggestion.
Russia deported all Kalmyks to Siberia in 1943 and around half of (97–98,000) Kalmyk people deported to Siberia died before being allowed to return home in 1957. The government of the Soviet Union forbade teaching Kalmyk language during the deportation.The Kalmyks' main purpose was to migrate to Mongolia and many Kalmyks joined the German Army. Marshal Khorloogiin Choibalsan attempted to migrate the deportees to Mongolia and he met with them in Siberia during his visit to Russia. Under the Law of the Russian Federation of April 26, 1991 "On Rehabilitation of Exiled Peoples" repressions against Kalmyks and other peoples were qualified as an act of genocide.