 According to sinologists Denis C. Twitchett and Klaus @-@ Peter Tietze , it is generally held that the Khitans emerged from the Yuwen branch of the Xianbei people . Following a defeat at the hands of another branch of the Xianbei in 345 , the Yuwen split into three tribes , one of which was called the Kumo Xi . In 388 the Kumo Xi itself split , with one group remaining under the name Kumo Xi and the other group becoming the Khitans . This view is partially backed up by the Book of Wei , which describes the Khitans as being of Xianbei origins . There are also several competing theories on the origin of the Khitans . Beginning in the Song dynasty , some Chinese scholars suggested that the Khitans might have descended from the Xiongnu people . While modern historians have rejected the idea that the Khitan were solely Xiongnu in origin , there is some support for the claim that they are of mixed Xianbei and Xiongnu origin . Beginning with Rashid @-@ al @-@ Din Hamadani in the fourteenth century , several Western scholars have theorized that the Khitans were Mongolic in origin , and in the late 19th century Western scholars made the claim that the Khitans were Tungusic in origin — modern linguistic analysis has discredited this claim . 
