One of the department's purposes was to select a dpon-chen, usually appointed by the lama and confirmed by the Yuan emperor in Beijing. "The Mongol dominance was most indirect: Sakya lamas remained the sources of authority and legitimacy, while the dpon-chens carried on the administration at Sakya. However there was no doubt as to who had the political clout. When a dispute developed between dpon-chen Kung-dga' bzari-po and one of 'Phags-pa's relatives at Sakya, the Chinese troops were dispatched to execute the dpon-chen." In 1253, Drogön Chögyal Phagpa (1235–1280) succeeded Sakya Pandita at the Mongol court. Phagpa became a religious teacher to Kublai Khan. Kublai Khan appointed Chögyal Phagpa as his Imperial Preceptor (originally State Preceptor) in 1260, the year when he became Khagan. Phagpa developed the priest-patron concept that characterized Tibeto-Mongolian relations from that point forward. With the support of Kublai Khan, Phagpa established himself and his sect as the preeminent political power in Tibet. Through their influence with the Mongol rulers, Tibetan lamas gained considerable influence in various Mongol clans, not only with Kublai, but, for example, also with the Il-Khanids. In 1265, Chögyal Phagpa returned to Tibet and for the first time made an attempt to impose Sakya hegemony with the appointment of Shakya Bzang-po (a long time servant and ally of the Sakyas) as the dpon-chen ('great administrator') over Tibet in 1267. A census was conducted in 1268 and Tibet was divided into thirteen myriarchies (administrative districts, nominally containing 10,000 households). By the end of the century, Western Tibet lay under the effective control of imperial officials (almost certainly Tibetans) dependent on the 'Great Administrator', while the kingdoms of Guge and Pu-ran retained their internal autonomy. The Sakya hegemony over Tibet continued into the middle of the 14th century, although it was challenged by a revolt of the Drikung Kagyu sect with the assistance of Duwa Khan of the Chagatai Khanate in 1285. The revolt was suppressed in 1290 when the Sakyas and eastern Mongols burned Drikung Monastery and killed 10,000 people.