Era of Fragmentation

The Era of Fragmentation is the two centuries between the fall of the Tibetan Empire and Mongol overlordship, the period during which the Tibetan nationality took shape without a state of its own. After the last emperor Langdarma was assassinated in 842, his supposed heirs Yumtan and Osung fought a civil war that dissolved imperial authority into rival princely lines: Osung's successors held Ngari in the west, Yumtan's held the central province of U, and local warlords with private armies and hill forts replaced the empire's administration. From this churn emerged the small kingdoms remembered by later chronicles — Purang-Guge and Maryul (Ladakh) in the west founded by the line of Kyide Nyigon, and polities such as Derge and Nangchen in the east. Between 842 and 1247 no central authority ruled the plateau; Buddhist monasteries survived in scattered strongholds, the Nyingma school endured persecution yet preserved its lineages in Amdo, and the monastic revival that spread from there back to U-Tsang laid the ground for the later Buddhist renaissance. The era closed when Mongol armies crossed the plateau in the 1240s and, in 1253, Drogon Chogyal Phagpa took charge of Tibetan affairs under the Yuan, opening the Sakya-Mongol relationship that bound Tibet to the empire of the Great Khan.