Military Architecture in England During the Middle Ages

by A. Hamilton Thompson

The keep had a traditional importance in the scheme of the castle, and the main energy of the castle-builders of the twelfth century was directed towards strengthening its power of resistance. But the improvement of siege artillery naturally turned their attention to the strengthening of the outer defences as well. The day of the palisade was past, and the stone curtain called for more scientific treatment than it had yet received. In the thirteenth century, then, military engineers began to concentrate their ingenuity upon the outer walls and entrances of the castle. Their interest was transferred by degrees from the keep to the curtain, while, at the same time, the domestic employment of the keep ceased in favour of the more comfortable quarters against the castle wall. In this way, as scientific fortification developed, the keep dropped into a secondary position, or was left out of the plan altogether.

pembroke: inner side of gatehouse

In tracing this gradual disappearance of the keep, it should be kept in mind that the stone keep, when we first meet with it, is actually a supplement of more permanent material added to a palisaded enclosure. In early walled enclosures, like Richmond or Ludlow, the stone defences made the special provision of a keep unnecessary: the whole castle, protected by its stone wall, had in itself the strength of a keep. It was only when it became likely that the stone curtain might show less resistance than its builders anticipated, that, in both the castles just mentioned, a tower-keep was provided. In both cases, the tower stood in the forefront of the defence of the principal ward of the castle. In the first instance it protected the curtain, while, if all else failed, its use, the primary use of such buildings, as an ultimate place of retirement for the defenders, could be demonstrated. During the reign of Henry II., the stone keep, whether a tower or a shell on the mound, was the dominating feature of the stone-walled castle. At Conisbrough and Pembroke ([181]) the great tower still keeps its pride of place, but the curtains of the ward in which it stands have been built or reconstructed with a view to effectual flanking; while the two semicircular towers which guarded the southern curtain of the inner ward at Pembroke were evidently an addition, after the keep had been built. In castles like Manorbier, the oldest parts of which are of the later part of the twelfth century, the builders returned to the original keepless plan of Richmond and Ludlow. The care, which, in the earlier castles, had been expended upon a single rallying point in the scheme of defence, was now applied to the whole outer wall of the castle, so that it began to offer a connected front to an attack.

During the transition, however, the keep, as we have seen, received its full share of attention. At Château-Gaillard ([163]) it was an integral part of one united design, the outer defences of which remain to be described. The great tower is at the highest point of the inner or third ward, which forms an irregular oval. But, before reaching this ward, two outer lines of defence had to be forced. There was only one possible approach for a besieging army, along the isthmus on the south-east side of the cliff. On this side the castle proper was protected by a powerful outwork, which offered a sharp angle to the isthmus. When Philip Augustus began to use his machines against the castle in February 1203-4, the round tower at the apex of this horn-work[242] was the main object of his attack. The sloping sides of the angle were flanked by two smaller round towers, while the entrance, close to the north angle, was covered on one side by a cylindrical tower, to which there was probably a corresponding tower in the opposite curtain. The horn-work was surrounded by an outer ditch. The strength of the curtain seems to have been little affected by the siege-engines. Breaches, both here and in the inner ward, were not made until Philip’s miners had weakened the masonry by boring galleries beneath it. A very deep ditch with perpendicular sides, cut in the chalk, stretched across the whole ridge, and divided the outwork from the middle ward, which was capped at the angles by cylindrical towers, and contained buildings of which the substructures, and some cellars excavated in the chalk, are left. The curtain of this ward was continued along the face of the precipice and the north-eastern slope, so as practically to enclose the inner ward. The two wards, however, were not concentric, for the inner ward occupied one end of the space enclosed by the middle ward, from which it was divided by a ditch. The wall of the inner ward was the most remarkable and original of the defences of the castle. Its whole outer face, save on the side next the precipice, was formed of a series of convex curves intersecting with each other, so that no flat surface was left. The wall is solid, and, looking at its fluted outer surface, we may well admire Philip’s military skill, which found it a not too formidable obstacle. A gateway in the east face gave access to the inner ward from the narrowest portion of the middle ward, and the ditch at this point was originally crossed by a stone causeway. The projecting spur of the great tower faced the gateway. The whole formidable design was perfect from the point of view of flanking, while the plan was a step towards the concentric arrangement of one ward within another. The prominence of the keep in the plan was, however, an archaic feature; and the history of the siege of 1204 shows very clearly that the great tower was practically a superfluity, and that the last hopes of the defenders were centred in the wall of the inner ward. When Philip’s miners had endangered its stability, and his engines were brought to play upon the weakened stonework, their hope was lost.[243]

The inventive skill shown in the inner wall of Château-Gaillard was not displayed again in the same form. But a step in the flanking of the curtain by round towers is seen in the wall of Conisbrough ([217]). Here the inner ward is nearly oval, and the southern half of the curtain, in which is contained the entrance from the outworks, is strengthened by small solid towers with battering bases, projecting some two-thirds of a circle from the wall.[244] Such solid projections for flanking purposes are found at Scarborough and Knaresborough, and could be easily added to an earlier wall, when necessity required. For the convenience of the defenders, however, larger towers with rooms on each floor were desirable; and the actual improvement of the defences of the curtain is seen in the multiplication of such towers, so as to leave no part of the wall unflanked. The circular or polygonal form was almost universally adopted for them.

conisbrough: barbican of inner bailey