Уйгурский каганат
The Uyghur Khaganate stretched from the Caspian Sea to Manchuria and lasted from 744 to 840. It was administered from the imperial capital Ordu-Baliq, one of the biggest ancient cities built in Mongolia. In 840, following a famine and civil war, the Uyghur Khaganate was overrun by the Yenisei Kirghiz, another Turkic people. As a result, the majority of tribal groups formerly under Uyghur control dispersed and moved out of Mongolia.