Soviet historiography, more specifically Soviet, "Uyghur Studies" were increasingly politicized to match the tenor of the Sino-Soviet split from the 1960s and 1970s. One Soviet Turkologist, Tursun Rakhminov, who worked for the Soviet Communist Party, argued that the modern Uyghurs had founded the ancient Toquz Oghuz Country (744–840), the Kara-Khanid Khanate (840–1212), and so forth. The premodern states' wars against Chinese dynasties were cast as struggles for national liberation by the Uyghur ethnic group. Soviet historiography was not consistent on such questions. When Sino-Soviet relations were warmer, for example, the Three Districts Revolution was portrayed by Soviet historians as part of opposition to the Kuomintang during the Chinese Civil War, not an anti-Chinese bid for national liberation. The Soviets also encouraged migration of Uyghurs to its territory in Kazakhstan, along the 4,380 km (2,738 mi) border. In May 1962, 60,000 Uyghurs from Xinjiang Province crossed the frontier into the Soviet Union to flee the famine and economic chaos of the Great Leap Forward.