库苏古尔省
It is most likely that the ancestors of modern Buryats are Bayyrku and Kurykans who were part of the tribal union of the Tiele. The Tiele, in turn, came from the Dingling. The first information about Dingling appeared in sources from the 2nd century BC. The name "Buriyad" is mentioned as one of the forest people for the first time in "The Secret History of the Mongols" (possibly 1240). It says Jochi, the eldest son of Genghis Khan, marched north to subjugate the Buryats in 1207. The Buryats lived along the Angara River and its tributaries at this time. Meanwhile, their component, Barga, appeared both west of Baikal and in northern Buryatia's Barguzin valley. Linked also to the Bargas were the Khori-Tumed along the Arig River in eastern Khövsgöl Province and the Angara. A Tumad rebellion broke out in 1217, when Genghis Khan allowed his viceroy to seize 30 Tumad maidens. Genghis Khan's commander Dorbei the Fierce of the Dörbeds smashed them in response. The Buryats joined the Oirats challenging the imperial rule of the Eastern Mongols during the Northern Yuan period in the late 14th century.