Undoubtedly, the largest empire in the existence of human history was the Mongol Empire, once a hodgepodge of warring nomadic tribes from Central Asia before banding together under the banner of Temujin, better known as Genghis Khan.
But what was the key to the Mongol Empire's size? Was the horse, the most ideal creature to use for long-distance travel, the exclusive reason? Or were there other factors involved?