 The extras used for the battle scenes were mostly members of the  F.C.A., the Irish version of the territorial army. As they were  drawn from many different army companies, and the members of these  are usually drawn from the same locality, local rivalry between such  companies is common. Apparently, some of the battle scenes seen in  the movie are far more realistic than you might imagine, with rival  companies actually using the occasion to try the beat the lard out  of each other.