Boltscar, keep your men alive by:
* Raising your tactics skill. This will give you numerical advantage in battle.
* Telling your men to "hold" "follow" and "charge" at the right moments. If you start on a hill for example and have ranged troops (troops with bows, stones, whatever), tell them to hold and they will pepper oncoming enemies with missiles.
* Infantry can swamp horsemen. Just let the cavalry come and order your men to charge at the last moment. The horses will be caught in the fray, rear up, get stuck and die.
* Horsemen can easily kill off infantry on flat terrain. When faced with lots of enemy archers, however, lead your troops yourself, taking a route that offers cover. At close range, set the cavalry loose

* Last but definitely not least: YOU are the hero! Charge in, kick ass and take names so your men don't have to! You are the biggest support they have, in fact
Have fun!
Edit: also don't forget to feed your men!
