War hammers were developed as a consequence of the prevalence of surface-hardened steel surfacing of wrought iron armors of the late medieval battlefields during the fourteenth and fifteenth centuries. The surface of armors had become as hard as the edge of a blade, so blades tended to ricochet. Swords and battleaxes were likely to give only glancing blows, losing much of their impact, especially on the high curvature of helmets. A war hammer could deliver the full force of a blow to the target.
War hammers, especially when mounted on a pole, could damage without penetrating armor. In particular, they transmitted their impact through even the thickest helmets and caused concussions. Later war hammers often had a spike on one side of the head, making them more versatile weapons.