The bishop of Acre was correct in thinking that a great King had conquered Persia; however "King David", as it turned out, was Tengrist warlord Genghis Khan.
The link between Prester John and Genghis Khan was elaborated upon at this time, as the Prester became identified with Genghis' foster father, Toghrul, king of the Keraites, given the Jin title Ong Khan Toghrul.