 The Mongols first demanded tribute from Pagan in 1271 – 72 , as part of their drive to encircle the Song dynasty of China . When King <unk> refused , Emperor <unk> Khan himself sent another mission in <unk> , again demanding tribute . It too was rejected . In 1275 , the emperor ordered the <unk> government to secure the <unk> in order to block an escape path for the Song , and permitted a limited border war if Pagan contested . Pagan did contest but its army was driven back at the frontier by the <unk> Army in <unk> – 78 . After a brief lull , <unk> Khan in 1281 turned his attention to Southeast Asia , demanding tribute from Pagan , the Khmer Empire , <unk> <unk> and <unk> . When the <unk> king again refused , the emperor ordered an invasion of northern Burma . Two dry season campaigns ( <unk> – 85 ) later , the Mongols had occupied down to <unk> and <unk> , forcing the <unk> king to flee to Lower Burma . The Mongols organized northern Burma as the province of <unk> . 
