Agree with you on all but the last example; I think the Mongol Empire was one of the marvels of human history, in terms of sheer size and coordination. It succeeded in uniting friendly tribes and warring tribes alike by allowing them to retain their cultural traditions and self-administrate, so long as it didn't violate Mongol law.<p>Unfortunately, the government that developed was mostly a dictatorship, and as usual it was relatively short-lived once some key family members died off and left an opportunity for others to squabble.