Yelü Dashi
In 1122, the Jürchen Jin dynasty took the Southern Capital of the Liao dynasty, and the remaining Khitans fled in two groups to the west. One group led by Xiao Gan fled to Xia where they set up a short lived Xi dynasty that lasted only five months before Gan died at the hands of his own troops. The other group, led by Yelü Dashi, joined Emperor Tianzuo of Liao at the Xia border. In the early summer of 1123, Dashi was captured by the Jin and forced to lead them to Tianzuo's camp, where the entire imperial family except for Tianzuo and one son were captured. Tianzuo sought refuge with Chongzong, who while initially receptive, changed his mind after warnings from the Jurchens and declared himself a vassal of Jin in 1124.