evidence: The territory of modern-day Mongolia has been ruled by various nomadic empires, including the Xiongnu, the Xianbei, the Rouran, the First Turkic Khaganate, the Second Turkic Khaganate, the Uyghur Khaganate and others. In 1206, Genghis Khan founded the Mongol Empire, which became the largest contiguous land empire in history. His grandson Kublai Khan conquered China proper and established the Yuan dynasty. After the collapse of the Yuan, the Mongols retreated to Mongolia and resumed their earlier pattern of factional conflict, except during the era of Dayan Khan and Tumen Zasagt Khan. [...] After the establishment of the People's Republic of China, both countries confirmed their mutual recognition on 6 October 1949. However, the Republic of China used its Security Council veto in 1955, to stop the admission of the Mongolian People's Republic to the United Nations on the grounds it recognized all of Mongolia —including Outer Mongolia— as part of China. This was the only time the Republic of China ever used its veto. Hence, and because of the repeated threats to veto by the ROC, Mongolia did not join the UN until 1961 when the Soviet Union agreed to lift its veto on the admission of Mauritania (and any other newly independent African state), in return for the admission of Mongolia. Faced with pressure from nearly all the other African countries, the ROC relented under protest. Mongolia and Mauritania were both admitted to the UN on 27 October 1961.[41][42][43] (see China and the United Nations)