The Development of Castles

The Ringwork Castle
The first castles in western Europe were built in the 10th century but became much more widespread from 1020. The earliest type of castle consisted of a simple ringwork. The ringwork comprised a circular earth bank surrounded by an external ditch, surmounted with a palisade (a tall, sturdy fence made of wooden stakes). The entrance was a defended gatehouse, and inside the ringwork were wooden buildings, usually dwelling houses, storehouses, and a well. In England about 200 of these ringwork castles were built between 1066 and 1215.

The Motte and Bailey Castle
The motte and bailey castle was a more advanced form than the ringwork castle. The motte was an artificial mound on which stood a wooden tower. The base of the motte was surrounded by a ditch; earth and stones that were dug away to make the ditch were used to build the motte. Just inside the ditch, at ground level below the motte, was the bailey, a courtyard that was usually oval or kidney-shaped, and that was enclosed by another ditch and bank. The bank was fortified with a wooden palisade, or later on, with a stone wall, known as an enceinte or outer wall.
In time, the crude ditches that acted as the outer defences of earlier motte and bailey castles were replaced with wide, deep moats that were either dry or filled with water. Access to the castle was by a drawbridge, which could be raised and lowered over the moat from within the castle. Some gateways were protected by a walled outwork known as a barbican. The gateways themselves were often closed by a portcullis-a thick iron-plated wooden door that could be pulled up into a cavity in the wall above or quickly lowered to stop anyone entering the castle.
Today, all that remains of these motte and bailey castles are grassy mounds that were once mottes (about 700 of them can be seen in Britain today). However, an idea of what these castles looked like may be gained from the Bayeux Tapestry; its pictorial narrative shows the 11th-century castle of Rennes and Dinan, in Brittany, and of Bayeux, in Normandy.

The Keep Castle
The next stage of development was the keep castle. The keep, or donjon, was a rectangular tower built to withstand siege. It had very thick stone walls buttressed at the base with a sloping plinth. There were virtually no windows, and the entrance was by means of a flight of stone steps leading to first-floor level. On the ground floor were a well sunk into the floor of the keep, kitchens, and storage rooms. Dwelling quarters were situated on the floors above and were reached by means of moveable ladders, or by staircases built into the walls.
The disadvantage of the rectangular keep was that, from within the walls, it was impossible to see what an enemy was doing round the corner of its angles. One solution to the problem was to build angle turrets, small towers built on to the corners of the keep; however, these were vulnerable to undermining by a skilled enemy. Later keeps were often circular or polygonal. Circular keeps are thought to have originated in France in the 12th century. One advantage of a circular keep was that it made possible all-round vision; another was that cannon fired at the walls tended to glance off the curved walls rather than penetrate them. As time went on, living and administrative quarters were generally moved from the keep to new buildings within the bailey. The keep, which then had a purely defensive purpose, became stronger and smaller.

The Concentric Castle
During the 12th and 13th centuries, castle-building was refined and improved. A castle's strongest point was no longer the keep; its strength was now concentrated in the walls. Walls were set with strongly fortified gatehouses and with towers at regular intervals all round their circumference. The gatehouses and towers were machicolated, or built in such a way that large stones, boiling oil, or other missiles could be dropped through the floor on to the enemy below. The tops of the walls were also crenellated, or set with regular recesses through which archers could shoot in relative safety. This change was partly brought about by the use of a new weapon, the crossbow, which was capable of delivering a far longer-range shot than earlier bows. It was both to enhance its defensive power and to fend off enemies armed with crossbows that soldiers were now stationed on the castle walls, on wall towers, and in gatehouses.
This led to the development of the concentric castle, which was defended by walls within walls. The origins of the concentric castle lay in the tendency to wall the outer bailey once the inner bailey had been enclosed by a wall. The walls of the outer bailey were usually less substantial than those of the inner bailey: their purpose was to protect the less important outbuildings, to keep attackers away from the inner defences so long as the outer ward could be held. Two sets of defensive walls set close together also allowed archers manning the top of the inner wall to fire down above the heads of their comrades defending the outer wall and also to shower the inside of lower ramparts with arrows if attackers managed to penetrate the outer wall.
In Britain, the finest examples of concentric castles are those built by Edward I at the end of the 13th century to secure his conquests in Wales; of these, the finest is Beaumaris, on Anglesey. (Caernarfon, Conwy, and Harlech castles are other fortresses built by Edward I.)