Castle Defences in the 12th Century

Castle defences had to stand against an increasingly sophisticated range of siege engines. An obvious means of defence was the thickness of the wall which would be proof against the blows of the ram or the slow labour of the pick. But a thick wall could not protect against a persistent and well-coordinated siege.

An example is the siege of Château Gaillard by Philip II of France. The castle was defended by successive lines following an elongated plan, with the donjon as the most important part. The inner wall was very strong, specifically designed to resist the siege engines. After a long blockade, with communications cut off for months and the garrison greatly reduced in numbers, it finally yielded to the miners, reinforced by the great Trébuchet.

Castle defences under attack: the battering ram in action, protected by the penthouse

Against the great catapults the besieged could not do too much. Integrating the heavy engines into castle defences was always a problem. The use of the machines upon the walls themselves was dangerous to the stability of the masonry and hastened the chance of a breach. On the other hand, they could not be employed from the interior of the enclosure, without endangering the defenders on the rampart. The summit of the rectangular keep of the 12th century was never intended to be used as an artillery platform. The engineers probably feared the effect of the constant vibration upon the flat wooden roof, and were satisfied with concealing their ridged roofs within high ramparts.

The defenders had to resort to other means. Among them, the individual crossbow was intensively used. The wheeled belfries formed a direct target for the arrows. From their superior position upon the ramparts, the defenders could also throw down stones and burning material upon the assailants engaged at the foot of the wall.

The chief engine used against the walls was the battering ram, a huge pole with an iron head. Against the ram, the defenders let down grappling irons or beams with forked heads, which gripped and disabled it. Sacks of wool or earth could be lowered to meet its strokes.

The assailants were protected by penthouses and mantlets, with their solid tops and sloping surfaces designed to stand against the shock of stones and arrows. The penthouses had a rounded or gabled top, called the "tortoise", covering the machine. The roof was very solid, such as to resist missiles thrown from the ramparts, and the whole was covered with raw hides or some other incombustible material to protect against fire.

The first improvements in castle defences consisted in the protection of the ramparts. Behind the outer parapet of the wall was the rampart-walk, a level path along the top of the wall, which was sometimes protected by a parapet in the rear. The upper portion of the parapet had openings called crenellations. Through them, an archer could command a limited part of the field, at right angles to the wall.

The crenellations were narrow compared with the parapets between them. Even in advanced examples of fortification like the ramparts of Aigues-Mortes and Carcassonne, the parapets are still very broad, although they are pierced by arrow-slits. But the arrow-slits did not allow for a good command of the wall base from behind the parapet.

Castle defences: Section through hoardings (right side of the parapet)

As a result, in time of siege it became customary to supply the walls and the donjons with shed-like projecting wooden galleries, known as hoardings (brattices), which could be entered through the crenellations. They improved the defenders’ field of fire along the wall, and directly at the wall base. In their floor there were holes, through which missiles could be fired against the besiegers engaged at the base of the wall. Slits in the outer face were still available for straight firing. The defenders of the ramparts were thus protected, having a much better command of the field and the foot of the wall.

The image on the left is showing a section through the hoardings, which project out from the parapet, and the inner gallery, which covers the rampart walk. The joists of the flooring, often common for both galleries, passed through holes at the foot of the parapet.

The round keeps or donjons had a spreading base and buttresses, to keep the battering ram and bore from direct contact with the main wall of the tower. The flanking position of the defenders was improved, while missiles dropped from the top upon the sloping surface would rebound upon the enemy with deadly effect.

Despite the usual precautions against fire, the wooden castle defences were still vulnerable to the arrows tipped with burning tow, or the more formidable red-hot stones fired by catapults.

With the advancement of fortifications, machicolations took the place of the hoardings. They had the same purpose, but they were permanent masonry constructions, projecting outwards from the wall, and of much greater strength due to the stone battlements. The donjon and the towers of the enceinte were usually bratticed at the rampart level.

Timber castle defences were supplementing stone walls till a late period, however, corbelled-out parapets with machicolations already appeared before the end of the 12th century.