Shan political power increased after the Mongols overran Pagan in 1287 .
The Shans came to dominate many of the northern to eastern areas of Burma -- from northwestern Sagaing Division to the present - day Shan Hills .
Shan political power increased after the Mongols overran Pagan in 1287 and the Shans came to dominate many of the northern to eastern areas of Burma -- from northwestern Sagaing Division to the present - day Shan Hills .