After the Mongol Prince Köden took control of the Kokonor region in 1239, in order to investigate the possibility of attacking Song China from the West, he sent his general Doorda Darqan on a reconnaissance mission into Tibet in 1240. During this expedition the Kadampa (Bka'-gdams) monasteries of Rwa-sgreng and Rgyal-lha-khang were burned, and 500 people killed. The death of Ögödei the Mongol Khan in 1241 brought Mongol military activity around the world ground, temporarily, to a halt. Mongol interests in Tibet resumed in 1244 when Prince Köden sent an invitation to Sakya Pandita (1182–1251) to come to his capital and formally surrender Tibet to the Mongols. Sakya Pandita arrived in Kokonor with his two nephews 'Phags-pa (1235–80) and Phyag-na Rdo-rje (1239–67) in 1246.