Genghis Khan: Crazy Killer, or Strategic Genius?

I see Genghis Khan as a strtegic genius more than a crazy killer. Do not get me wrong he was responsible for a lot of deaths, but they did serve to benefit him. Whenever he wanted to kill people, it was motivated killing, he did not just think to himself, "hey I really want to go kill all those people in the village over, that sounds fun", instead he thought, "those people are my enemies and I need to eliminate them while they are distracted so my people are ot harmed". Genghis was also brought up in a very brutal part of the world where it was normal to see death. Killing or harming people was a way to survive, so when he was plotting invasions to kill many people, it was not killing to kill, it was killing to survive. Also, I think if Genghis Khan was a psychotic man motivated by ending lives, he would have executed his former best friend when he was captured. Instead he could not even watch as the man he now called his greatest enemy, who had invaded him multiple times, was executed. Genghis Khan clearly used his killing methods strictly for strategy and not for some kind of sick pleasures.