One tidbit to add, once you get Swordstaff men if you put a long, thin line of Norse Archers on a wall right in front of a line of swordstaves you will not lose that wall no matter what the enemy throws against it. Same for hill tops, for the most part, although it that case I like to walk the swordstaves forward in spearwall through the NA to prevent heavy losses against a charge. With Norse Archers available at low castles, Swordstaves from medium cities, and Norse War Clerics from Abbeys you can conquer the world. I made extensive use of NA throughout my Viking Migration AAR, they're an excellent second line or flanking unit and an average melee and archer unit at the same time.