'Mandate of Heaven' is a philosophical idea used by chinese emperors to justify the legitimacy of their rule. in western coutries kings and emperors invented similar ideas such as divine rights of monarchy for the same purpose. in modern world, every regime too uses the idea of "rule of the people'' namely "democracy" for legitimacy of rule.
china did invaded quite a few countries in past five thousand years but 'mandate of heaven' has little to do with china's invaision against other countries though i am sure they would find some other excuses if not 'mandate of heaven'. since the day the human being were created, the wars between tribes, states, empires never stop.The people killed their neighbours, sack their wealth, grab their women, and occupy their lands. that is the way how jungle law applied to the human society. then came the several major human civilizations and empires, which seperate the world militarily and culturally in their spheres. (actually there were only 20 independent countries before WWII) meanwhile the manner they acquire resources were more civilized. that is how the world worked and how the civilization were disseminated in the ancient time.
in east aisa, the relationship between china and its neigbours is called "tributary system", these small countries (Korea, Japan, Ryukyu,Vietnam, Burma,etc.) paid symbolic "tribute" to china and acknowledged china as a sovereign govenment while maintain their kingdom as a self-government. Actually, china did not have too much interests in invading small neighbors cause china was an agricultural civilization the running of which was primarily based on tax. invading its small negibhours was totally unprofitable (total 'GDP' of mongolia is even much smaller than a south china county) but very costy (even maintaining the rule in Xinjiang and Northeast China making the central government difficult to sustain). china's military operations against its neigbhours were primarily out of national defense purpose or stablilty concerns.
Compared to other historical empires, Chengis Khan (Sack, Kill, Rape), Rome and Greece (Conquer and enslave), Britain and Spain ( Genocide and colonise), Eastern tributary system was most humane and civilized system.
And a strange interpretation as well.
