@sorakasturi
If this is going full medieval, usually it WASN'T the peasants doing the fighting, it was small armies of soldiers and knights who have been raised since birth to fight, essentially.
Commoners fighting was rare, because they had to be busy taking care of the farms and fields, to provide food for the actually warriors.
Only when we developed methods to farm more efficiently and make more food, the ability to field larger armies with commoners as cannon fodder was possible.