Kublai Khan and the Civil War

The theme that in many ways prevented them from doing even more so was the fact that they started fighting with each other. They conquered a humongous amount of land, an extremely short amount of time. Once it devolves, like you said, once you're killing, once brothers are killing each other, it's not something that just happens. No one needs to teach that. Education is what we need, teaching them when they're young is what you need to do to keep them from doing this.