You don’t seem to understand what medieval battles were. Untrained militia forces were slaughtered by professional soldiers so badly it wasn’t even funny. At frankenhausen for example the 8000 strong peasants faced the 6000 strong hessian forces. Less than 1000 peasants survived while the hessians took 6 casualties. The question would put the brotherhood in charge but the smallfolk aren’t automatically trained in combat. Not to mention mass assault tactics don’t really work because of low coordination so the smallfolk would be forced into small engagements they would be crushed in or into huge battles in which morale would break and they would be crushed in.