A crucial
battle over a small area - Agincourt, Poitiers, Crecy - can ultimately determine the control of an entire territory: Normandy, Anjou, Aquitaine.
With those weapons of, er, light destruction, you'll simply go from
area to
area battling small groups of the same enemy grunts
over and
over, with the occasional big guy thrown in for good measure, although he doesn't really add much of a dynamic to the combat.