耶律大石
Robert Silverberg connects this account with historic events of 1141, when the Qara Khitai khanate under Yelü Dashi defeated the Seljuk Turks in the Battle of Qatwan, near Samarkand. The Seljuks ruled over Persia at the time and were the most powerful force in the Muslim world; the defeat at Samarkand weakened them substantially. The Qara Khitai at the time were Buddhists, not Christians, and there is no reason to suppose Yelü Dashi was ever called Prester John. However, several vassals of the Qara Khitai practiced Nestorian Christianity, which may have contributed to the legend. It is also possible that the Europeans, who were unfamiliar with Buddhism, assumed that if the leader was not Muslim, he must be Christian. The defeat encouraged the Crusaders and inspired a notion of deliverance from the East. It is possible Otto recorded Hugh's confused report to prevent complacency in the Crusade's European backers – according to his account, no help could be expected from a powerful Eastern king.