Loose foot and loose mounted troops have the ability, at their option, to withdraw from ranged or melee combat, thereby reducing damage by the amount of hexes the move away (at least that is what the game seemed to imply, it wasn't very clear) up to their full marching movement.
My question is, what stops a careful, fast-moving loose-mounted unit (such as light infantry with marching movement of 4, iirc) from being near invincible while peppering the flanks of the enemy?
Slightly on the subject, there's a guy named Dan Carlin who does a podcast called Hardcore History. I really enjoy them, and one of the most recent series he did was on Genghis Khan. He talked quite a bit about the Steppe horse archers and their brutally effective tactics against the Middle Eastern kingdoms and the armored knights and heavy infantry of Europe. If you like that sort of thing and have some time it's a fun listen.