The essentials of the transition from twelfth-century mail harness to the fully developed plate armor of the fifteenth century man-at-arms can be summarized as follows:
Articulations: Iron plate or hardened leather defenses for the elbows, knees, and shins first appeared in the mid-thirteenth century, and during the following hundred and fifty years protection for arms and hands, legs and feet became steadily more complete.
Torso: From the mid- to late thirteenth century, the torso of a well-equipped man-at-arms would be protected by a surcoat of cloth or leather lined with metal plates — a coat of plates, which by the mid to late fourteenth century would be supplemented, or wholly replaced, by a solid breast-plate. Underneath, a mail haubergeon continued to be worn, while it was still usual to wear coat armor on the outside, although there was much local variation in this. In England, for example, the surcoat was replaced by the short, tight-fitting jupon.
Head: In the early to mid-fourteenth century, the visored bascinet with attached mail aventail to protect the neck was replacing the round-topped great helm and coif for practical campaigning purposes. Visors came in a variety of forms. The simplest, common in Germany and Italy, consisted of a nasal which when not hooked to the brow of the bascinet would hang from the aventail at the chin. Often, indeed, men fought in bascinets without any form of visor.
Weaponry & Shielding: With the development of a fully articulated plate armor, the shield now became largely redundant. The emergence of plate armor also prompted a change in the man-at-arms primary weaponry. The sword with a flat blade, which provided an effective cutting edge against mail, was gradually replaced during the fourteenth century by one with a stiffer blade tapering to an acute, often reinforced point, designed for a thrusting action against plate armor.
The memorial brass of Sir Hugh Hastings (d.1347) in Elsing church, Norfolk. With flanking figures representing some of Hastings’ companions in arms, this is an intriguingly varied ensemble of body armor from the mid-fourteenth century. Note the visored bascinets, the skirted jupons, a curiously shaped kettle hat (bottom right), a pole-axe (bottom left) and the mounted figure of St George above Hastings’ head.
By the late fourteenth century, when this illumination was painted, men-at-arms normally fought on foot, rather than on horseback. Contemporary artists, however, continued to depict battle scenes as dramatic clashes of mounted knights.
Because the combat shown here took place on a bridge, the artist gave us a rare glimpse of how fourteenth-century men-at-arms actually deployed and handled their weapons when fighting as heavy infantry. As usual in medieval infantry battles, the defenders (left), able to maintain better order, ultimately won the fight.
Unless provided by a lord or patron, or possibly in fulfillment of a local community’s military obligations, the equipment of an aspiring man-at-arms would be his own responsibility. Although the mass-produced plate armor of the later middle ages may have been relatively less expensive than the mail hauberks of earlier centuries, equipping for war from scratch remained a costly business.
Consequently, the quality of a man’s arms and armor would have offered a clear indication of his place in the social hierarchy of the military elite. Much of the surviving evidence depicts the up-to-date harness of well-equipped noblemen; but, in reality, warfare in fourteenth-century Europe involved a heterogenous multitude of noblemen without prospects and gentlemen free lances, many of whom would have fought in armor of uneven quality.
Sources and suggested reading:
Warfare in the Medieval World by Carey, Allfree, and Cairns
Medieval Warfare: A History by Maurice Keen
Battle on bridge over Seine British Library Images Online