Mongols conquered Tibet

1240: Mongol ruler Godan Khan, the grandson of Genghis Khan invaded and conquered Tibet with 30.000 troops, looting monasteries and caused many victims. 
1244 Godan Khan considered religion a tool to control people. He wrote a letter to Sakya Pandita dema nding him to travel to Mongolia. The lama understood he could not decline the “offer” and traveled to the curt of the Khan in Lanzhou (Gansu), where he arrived in 1247. He was accompanied by Phagpa Lama, his nephew. Godan obviously was personally impressed by the Sakya Pandita and became his student. The Khan died shortly after the Sakya Pandita. His cousin Kublai Khan followed him on the throne. Thus a special relationship is installed which secured the supremacy of the Sakya-School in Tibet, the troops returned and annexed Kha m and Amdo. 
1247 Godan Khan bestows Sakya Pandita with the right to rule over the 13 Myriarchies (districts) of Tibet: reconstruction of (more or less) centralized rule over major parts of the country.
1254 Kublai Khan became a student of Chogyal Phagpa Rinpoche (1235 – 1280), the nephew of Sakya Pandita. Kublai made Phagpa the ruler or regent, ‘Desi’, of Tibet.
1281 Mongols controlled China completely under the Yuan Dynasty (1281-1368)
1287 A revolt of the Drikung Kagyüs with the support of Duwa Khan ended in 1290 when the Sakyas and Eastern Mongols burned down Drikung monastery and killed many people.