in the game it is mentioned that a primary strategy of humanity is heavy armor and the shield wall, but calvary was also a major thing especially after the invention of stirrups. Allowing for incredible mobility and crushing force. As it turns out, no amount of muscle or armor can protect you from being crushed by the 1100 pound animal trampling you, or the spear being wielded by the guy on top. In the steppes of Mongolia calvary was especially effective, horse archers were devastating and were used to great effect by the Mongolians in their conquest across Asia. That is to say, calvary is probably the best strategy humans have on offer. And also horses are cool, and i like them.