750 CE. After being defeated three times, half of the Oghuz-Tatar rebels rejoined the Uyghurs, while the other half fled to an unknown people, who were identified as Khitans or Karluks. According to Senga and Klyashtorny, part of the Toquz-Tatar rebels fled westwards from the Uyghurs to the Irtysh river basin, where they later organized the Kipchaks and other tribal groupings (either already there or also newly arrived) into the Kimek tribal union. According to the Russian orientalist Vasily Ushnitsky, reports of medieval Muslim sources about the Tatar origin of the Kimak dynastic clan are the argument of the supporters of the Mongolian origin of the Kimaks and Kipchaks. The news about the Tatars, from whom the Kimaks separated, according to Josef Markwart, confirms the fact of the movement to the west of the Turkified Mongolian elements. As for the division of Tatars who remained east, by the 10th century, they became subjects of the Khitan-led Liao dynasty. After the fall of the Liao, the Tatars experienced pressure from the Jurchen-led Jin dynasty and were urged to fight against the other Mongol tribes. The Tatars lived on the fertile pastures around Hulun Nuur and Buir Nuur and occupied a trade route to China proper in the 12th century. Southern Song ambassador Zhao Hong wrote in 1221 that in Genghis Khan's Mongol empire, there were three divisions based on their distance from the Jurchen Jin-ruled China: the White Tatars (白韃靼 Bai Dada), the Black Tatars (黑韃靼 Hei Dada), and the Wild Tatars (生韃靼 Sheng Dada), who were identified, by Kyzlasov, with the Turkic-speakers - including the Öngüds (of Turkic Shatuo origin), Mongolic speakers -to whom belonged Genghis Khan and his companions-, and the Tungusic speakers, respectively. The Secret History of the Mongols claimed that the Tatars were mortal enemies of the Mongols: they betrayed Khamag Mongol's khan Ambaghai to be executed by the Jurchen Jin dynasty and also treacherously poisoned chief Yesukhei, father of Genghis Khan; consequently, in 1202, Genghis Khan allied with Ong Khan, conquered the Tatars, and had Tatar men taller than a linchpin executed, and spared only women and children. The surviving Tatars were absorbed into Genghis Khan's tribe, and the Tatar confederation ceased to exist. Since the Tatars were a tribe of thousands, their absorption greatly enlarged Genghis Khan's tribe. Tatars and Mongols Mongolian historian Urgunge Onon proposes that Mongols were initially known to Europeans as Tatars