 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.