The immediate result of the war was the collapse of the Pagan Empire . However , the war merely accelerated the collapse but did not cause it . Pagan 's disintegration was " in fact more prolonged and agonized . " The kingdom had been in long gradual decline since the early 13th century . Had Pagan possessed a stronger central government , the collapse could have been temporary , and the country “ could have risen again ” . But the dynasty could not recover , and because the Mongols refused to fill the power vacuum , no viable center emerged in the immediate aftermath . As a result , several minor states fought it out for supremacy for the better part of the 14th century . It was only in the late 14th century that two relatively strong powers emerged in the Irrawaddy basin , restoring some semblance of normalcy . The vast region surrounding the Irrawaddy valley would continue to be made up of several small Tai @-@ Shan states well into the 16th century .