In the after-battle reports you'll get a list of units, how many casualties they took, how many blokes they killed, whether or not they earned any experience, and a total for the number of wounded who have returned to active duty.

Doctors, physicians and other healers in the retinue of the commanding general can help shift people from the 'dead' category to the 'recovered' category. Nothing is guaranteed, though.

Not all healers are available to all factions, by the way. Barbarians will never benefit from the services of a 'chirugeon', for example.