The Mongol prince Godan, a grandson of Genghis Khan, raided as far as Lhasa. During his attack in 1240, Prince Godan summoned Sakya Pandita (1182–1251), leader of the Sakya school of Tibetan Buddhism, to his court in what is now Gansu in Western China. With Sakya Pandita's submission to Godan in 1247, Tibet was officially incorporated into the Mongol Empire during the regency of Töregene Khatun (1241–1246). Michael C. van Walt van Praag writes that Godan granted Sakya Pandita temporal authority over a still politically fragmented Tibet, stating that "this investiture had little real impact" but it was significant in that it established the unique "Priest-Patron" relationship between the Mongols and the Sakya lamas.