Through the course of human history, commonplace objects have been pressed into service as weapons. Axes, by virtue of their ubiquity, are no exception. Besides axes designed for combat, there were many battle axes that doubled as tools. Axes could be modified into deadly projectiles as well (see the franciscafor an example). Axes were often cheaper than swords and considerably more available.
Battle axes generally weigh far less than modern splitting axes, especially mauls, because they were designed to cut legs and arms rather than wood; consequently, slightly narrow slicing blades are the norm. This facilitates deep, devastating wounds. Moreover, a lighter weapon is much quicker to bring to bear in combat and manipulate for repeated strikes against an adversary.
The crescent-shaped heads of European battle axes of the Roman and post-Roman periods were usually made of wrought iron with a carbon steel edge or, as time elapsed across the many centuries of the medieval era, steel. The hardwood handles of military axes came to be reinforced with metal bands called langets, so that an enemy warrior could not cut the shaft. Some later specimens had all-metal handles.
Battle axes are particularly associated in Western popular imagination with the Vikings. Certainly, Scandinavian foot soldiers and maritime marauders employed them as a stock weapon during their heyday, which extended from the beginning of the 8th century to the end of the 11th century. They produced several varieties, including specialized throwing axes (see francisca) and "bearded" axes or "skeggox" (so named for their trailing lower blade edge which increased cleaving power and could be used to catch the edge of an opponent's shield and pull it down, leaving the shield-bearer vulnerable to a follow-up blow). Viking axes were wielded with one hand or two, depending on the length of the plain wooden haft.
The war hammer consists of a handle and a head. The length of the handle may vary, the longest being roughly equivalent to that of the halberd, and the shortest about the same as that of a mace. Long war hammers were pole weapons(polearms) meant for use against riders, whereas short ones were used in closer quarters and from horseback.
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 the armor was now as hard as the edge of a blade, so a blade tended to ricochet. Swords and battleaxes were likely to only give a glancing blow, losing much of the impact, especially on the high curvature of the helmet. The war hammer could deliver the full force to the target.
War hammers, especially when mounted on a pole, could damage without penetrating the armour. In particular, they transmitted the impact through even the thickest helmet and caused concussions. Later war hammers often had a spike on one side of the head, making them more versatile weapons. A blade or spike tended to be used not against helmets but against other parts of the body where the armor was thinner and penetration was easier. The spike end could be used for grappling the target's armor, reins, or shield, or could be turned in the direction of the blow to pierce even heavy armor. Against mounted opponents, the weapon could also be directed at the legs of the horse, toppling the armoured foe to the ground where he could be more easily attacked.