The period of calm for Pagan ended in the early 1270s . By then , the Song were on the ropes , and Emperor Kublai Khan , who officially founded the Yuan dynasty on 18 December 1271 , sought to cut off the retreat of Song refugees in all directions . In Pagan 's case , he had ordered the Mongol governor of Dali to tighten control of the borderlands , and in January 1271 to send a mission to Pagan to demand tribute . The tribute he demanded was nominal . Given his higher priority preoccupations elsewhere , the emperor was not looking to replace the regime at Pagan . At the border , the ruler of the Wa and Palaung regions submitted to the Mongols .