 Then as now, the borderlands mostly consist of forbidding terrains of high mountain ranges.The Mongol Empire first arrived at the doorstep of the Pagan Empire in 1252 by invading the Dali Kingdom in its attempt to outflank Song China.The Mongol armies captured the capital, Dali, on 7 January 1253, and went on to pacify much of the kingdom by 1257.