sentences:  Kuchlug's forces had been battling the powerful Khwarezmian Empire, whose leader was the Muslim Muhammad II of Khwarezm.Rumors circulated in Europe that Kuchlug was the mythical Prester John, again battling the Muslims in the East.During the Fifth Crusade (1213–1221), as the Christians were unsuccessfully laying siege to the Egyptian city of Damietta, the legend of Prester John became conflated with the reality of Genghis Khan's rapidly expanding empire.