During the First Mongol invasion of Burma, the fort at Ngasaunggyan was overrun after a two-month siege.

The first Mongol invasions of Burma were a series of military conflicts between Kublai Khan's Yuan dynasty, a division of the Mongol Empire, and the Pagan Empire that took place between 1277 and 1287. The invasions toppled the 250-year-old Pagan Empire, and the Mongol army seized Pagan territories in present-day Dehong, Yunnan and northern Burma to Tagaung. The invasions ushered in 250 years of political fragmentation in Burma and the rise of ethnic Tai-Shan states throughout mainland Southeast Asia.

Yingjiang County is a county in Dehong Prefecture, Yunnan province, China, bordering Tengchong to the east, Lianghe County to the southeast, Longchuan County to the south and Burma's Kachin State to the west.