In medieval Europe the first castles appeared in the 9th century, when the Carolingian empire was collapsing as a result of Viking and Magyar raids. As central authority disintegrated, nobles fought for power and territory. They built castles so that they could control and defend their land. These castles started out as simple, wooden structures, relying on natural defences such as rivers or hills, but soon builders were adding earthworks - mounds, banks and ditches - for extra defence. Earthworks could be mounds, called mottes, or round, raised enclosures, called ringworks. A motte was topped by a wooden tower; while a ringwork contained buildings protected by a wooden palisade. In each case earth was dug from the perimeter area, leaving a protective ditch.
The fragmentation of land into separate estates or domains, and the manner in which they were ruled, led to the development of feudalism. The most powerful men, the counts, dukes and kings, controlled more than one estate. They would keep some of the land for themselves and give control of the rest to other lords. In return these lords promised to provide knights for their overlord's wars and for the garrisoning of their overlord's castles. In theory, a person's allegienace was always to their overlord, however there were constant battles for land and power and some men became almost as powerful as their overlord. One such man was William, Duke of Normandy. After many years of war he had become very powerful and a real threat to his overlord, the king of France. In September 1066, he launched an invasion of England to enforce his claim to the English throne. Castles played an important part in European warfare, and William brought this knowledge with him. He built his first defensive structure within the walls of the old Roman Fort at Pevensey where his invasion force had landed. He then continued to build castles to defend his line of retreat and within two weeks of landing had built castles at Hastings and Dover. After his victory at the battle of Hastings he went to London where he was crowned King of England, on Christmas Day 1066. The period of Norman castle building had begun.
As William's forces spread across the country they built castles as a means to subdue and control the populace. William claimed all the land as his own but gave grants of land (fiefs) to the Norman lords that had provided him with military assistance during the invasion. In order to prevent any of them achieving the level of power that he had acquired in France, he gave them many separate estates spread across the country so that it would be difficult for any one lord to join all his forces together in a single power base. In order to protect and control their new lands the lords built castles on each of their estates. By the time of William's death, in 1087, there were 86 Norman castles in England.
The motte at Skipsea Castle
The early castles were mainly 'ringworks' or 'motte and baileys' which were quick to construct. A 'motte and bailey' castle consisted of a large mound, or motte, where possible based on solid rock, and made of compacted rubble and earth, topped with a wooden tower. It provided a look-out post, as well as adding tactically important height if the castle was attacked. The 'bailey' was a large, level enclosed area beside the motte, surrounded by an earthwork bank and ditch, topped with a timber palisade. The bailey often contained a hall, buildings for livestock, a forge and armoury, and a chapel. Due to the use of wood in their construction, these castles were particularly vulnerable to fire.
Recreation of a Norman bailey at Mountfitchet Castle
Many of these early wooden castles were later rebuilt in stone making use of the old earthworks. Stone castles needed more workers, were more expensive, and took much longer to build than wooden ones, but they were fireproof and much more secure.
The White Tower at the Tower of London
The first stone castles were usually centred on a large tower. In 1079, work started on a great stone tower at London, now known as the White Tower, at the Tower of London, and at a similar time at Colchester Castle. The great stone tower, donjon, or keep was much stronger than its timber predecessor, and its height gave defending soldiers a good view and better line of fire. A great tower provided secure storage for money and documents as well as offering more comfortable accommodation for the nobles.
Castle builders turned the unique character of each site to their advantage, and keeps were built to many different designs, including rectangular, circular, square, multi-sided and D-shaped. At Portchester, the Norman keep was built inside the walls of an existing Roman fort. Others, like Chepstow, turned natural features such as sheer cliffs to their advantage, using the added protection they provided on one or more of the castle's flanks.
An example of a shell keep at Restormel Castle
A variation on the standard keep was the shell keep. A tall circular wall was built around the top of a motte, and all the most important buildings were placed inside, against the walls of the shell. The best example is Restormel Castle in Cornwall, and others can be seen at Totnes in Devon and Lewes Castle in Sussex.
Framlingham Castle relied on the defensive strength of its walls and towers rather than a large keep
Curtain walls with projecting towers (so that the area in front of the walls could be shot at by defenders in the towers) became a standard of castle design. A great tower was not a necessity with this type of defence because a hall and other rooms could be built inside the courtyard, or in the wall towers or gatehouse. The weakest part of these castles was the gateway and great effort was made to reinforce this part of the castle. The barbican was developed as a way to strengthen the entrance, by adding more defences in front of it, often a long corridor with multiple gates and portcullises, and holes above that defenders could use to fire on attackers below.
Concentric defences at Caerphilly Castle
During the 13th century, fortifications built to a concentric design began to appear. These castles had an inner circuit of curtain walls completely encircled by an outer circuit of walls, that were built low enough to allow an unobstructed line-of-fire from the inner walls. Beyond the outer walls, moats and further defences were often constructed. The idea may have come from knights who had seen the twin walls of the city of Constantinople during the crusades. Concentric castles had two main advantages: firstly, attackers had to get through more barriers; secondly, defending archers could stand on more than one set of walls, thus unleashing more firepower. Good examples of concentric castles can be seen at Beaumaris and Caerphilly in Wales, and at Dover Castle in Kent, generally considered to be the first British castle to feature a concentric design.
Conwy Castle one of the mighty castles built by Edward I to subjugate the Welsh
Once the Normans were firmly established in power, castle building proceeded at a more leisurely pace. However, political circumstances sometimes led to sudden spates of castle building. New castles might be constructed to reinforce the king's rule over a rebellious population or to protect the country from the threat of invasion. A good example is Edward I's campaigns in Wales between 1277 and 1284, which led to an extensive period of castle building, with mighty castles at Caernarfon, Conwy, Harlech and Beaumaris built to enforce English rule over the Welsh.
Elcho Castle a typical Scottish tower-house
In Scotland castles developed several distinctive features. The border country was subject to raids by both Scots and English for many centuries. In the 14th century small fortified towers, or 'peles', were built to protect local areas in northern England from these raids, while in Scotland, the distinctive 'tower-house' began to emerge. Scottish tower-houses had thick walls, battlemented parapets and strong turrets on the corners. Many were given the additional protection of extra walls, called 'barmkins', and ditches and banks. Iron gates called 'yetts' often protected the small doorways.