Mongolia, Korea and Vietnam----they cultures and languages have nothing in comon with China. Any annexation may cause unrest now.
even the status of taiwan remains unsettled when we share a same culture
yet the Mongolian empire collapased in less than 2 decades.it was impossible for them to go further west.how can they rule the vast land of china where rebellions came in a row while their own population kept falling after years of war.the total population of Mongolians at that time was no more...