Could you clarify what you mean, do you mean in the sense of any peasant class individual participating in a war or do you mean armed mobs with no training at all?

In Mughal North India, peasants were used as infantry, they were the cannon fodder in battle, many also worked supporting roles such as coolies, carriers, cooks, servants, etc. The main warriors were from kshtriya castes, professional soldiers who were officers, cavalry, elephant riders, general's, etc.

Under Akhbar the Great there was the Mansabdari system, every government official was expected to maintain an small army according to his rank, peasants, mercenaries etc were hired or conscripted and trained. The Mughlas were Turks and not Indians, so not a lot of them trusted locals, so they brought in adventurers and mercs from Persia and Central Asia. Akhbar however made alliances with the Rajputs, a tribe of ass kicking war lords belonging to Kshtriya Caste. Their society was a war like one, every able bodied man was expected to go to war. Thus since most of the armies at the time were composed of professional soldiers, peasants usually played a supporting role, unless there was a shortage of men.

I'll look for sources later.

For high and late medieval Western Europe, I think the definition of 'peasant' is important, because Medieval social structures had multiple de facto (and de jure) classes of untitled people, who could have very different material circumstances.

If by peasants, you mean 'the lower classes of serfs/villeins/tenant farmers, u/MI13 deals with their (non) use in the later middle ages here