By the 1270s , the Song economy had collapsed from the burden of taxes and inflation which the Song government used to finance its war against the Mongols .
Seeking to conquer China , the Mongol Empire launched a series of attacks on the Song .
By the 1270s , the Song economy had collapsed from the burden of taxes and inflation which the Song government used to finance China 's war against Mongol Empire Mongols .
Seeking to conquer China , the Mongol Empire launched a series of attacks on the Song .