I think the way it works is that how well a individual soldier can servive in combat is the combination of his armour value, defense skill (the soldiers individual skill at keeping enemy pointy things away from his fleshy bits), and his shield. I seem to remember some one here stating that the combat in TW games works like an RPG when a soldier attacks another, , there is a combat roll of his attack value verses his opponents defense value, this is for 1 count'em 1 soldier in a unit of 80 or 120 (it's repeated for every guy in the unit). If the attack succeds then it takes away 1 hit point from that particular soldier in that unit. But since most guys only have 1 hit point it means they die. But if the unit has 2 or 3 hit points it will take 2 or 3 sucessful attacks to kill 1 soldier of the unit. IIRC Arcani and most chariots types have 2 hit points and elephants have 3.