I would suggest looking in to the origins of the “company” for professionalization of the military in the renaissance. Before that it depends on where you were, but lords were generally responsible for raising and arming vassals for the kingdoms campaigns. The level of equipment and training varies, but there are interesting examples like english yeomanry.

Re peasant revolts these were almost never popular class uprising AFAICT. It looked a lot more like a commoner or minor noble taking on a warlord position against the local rulers. Think of afghanistan or parts of NE africa for equivalants.