In 1221, Jacques de Vitry, Bishop of Acre, returned from the disastrous Fifth Crusade with good news: King David of India, the son or grandson of Prester John, had mobilized his armies against the Saracens. He had already conquered Persia, then under the Khwarezmian Empire's control, and was moving on towards Baghdad as well. This descendant of the great king who had defeated the Seljuks in 1141 planned to reconquer and rebuild Jerusalem. Controversial Soviet historian and ethnologist Lev Gumilev speculated that the much reduced crusader Kingdom of Jerusalem in the Levant resuscitated this legend in order to raise Christian hopes and to persuade European monarchs who had lost interest by that time in getting involved in costly crusades in a distant region that was far removed from their own states and affairs.