© 1995-2015 Lise Hull
What is a castle? A castle is a properly fortified military residence. Why were castles built? Initially, they were designed and built to hold down conquered territory. They also served to intimidate and strike fear into the local peoples, were places of refuge, and places for the lords to live. They were also impressive symbols of the power and wealth of their owners. When were castles built? Norman castles were built from the 11th to 13th centuries.

Castles were brought to Britain by William the Conqueror, when he invaded England from his homeland in France. Known as the Duke of Normandy, William invaded England in 1066 and, due to his victory in the Battle of Hastings, William was crowned the King of England, and became King William I.

One of the most powerful ways for William to take control of his new kingdom, which included England, Scotland and Wales, was to have castles built throughout the land. At first, he ordered the construction of very simple castles, called motte and bailey castles.

They consisted of an earthen mound, called a motte, topped by a tower (first built of wood, and soon rebuilt in stone to make the towers more sturdy). The bailey was a large area of land enclosed by a shorter mound, placed next to the motte. Inside the bailey were the main activities of the castle (workshops, stables and livestock, household activities, etc.), while the tower on the motte was used as the lord's residence and as an observation post.

These earth and wood castles were not very sturdy, because the wood would rot fairly quickly and was easy for an enemy to burn. So, William the king ordered the construction of stone castles. Stone castles were much more sturdy, did not rot like wood, and also were much more able to withstand any attack by an invader. Over the centuries after William was king, other kings ordered elaborate castles to be built.

Castles were not just used by the king. Most castles, in fact, were granted by a king to their most loyal subjects, knights or barons who fought valiantly in battle and supported their king. The king, starting with William the Conqueror, gave his loyal knights vast estates and permission to build castles. In return, he expected these men (most of whom were given the titles of earl or lord) to control their lands as the king's representative, to keep the local population from rebelling, and to force them to work and pay rent to the lord (who then passed it onto the king).

Many of the people who lived in Britain before it was conquered did not like being controlled by the king's barons, and wanted to keep control of their own lands themselves. But that was not possible, because William and later kings (and queens) demanded they pay homage. Therefore, castles were built to establish the power of the king and his followers, and to keep the people from regaining control of their own lands.

These first knights and barons, followers of William the Conqueror, were known as the Normans, and were a very powerful lot. They built castles almost everywhere in Britain, hundreds of which still survive.

Stone castles were built for stability and to symbolize the power of the lords of the kingdom. Even if the king did not order a particular castle to be built for his use, he still retained the ability to seize any of his lords' castles if they displeased him or if the king had a special reason to want to use it.

The features that made stone castles stable and able to withstand battle include the following:

• The walls were very thick, anywhere between 8 and 20 feet in thickness, so they could withstand bombardment or battering from a battering ram, or another siege engine (like a trebuchet or catapult).

• Over time, the shape of the towers changed as castle- builders experimented with designs that were less likely to fall down in battle or from the instability of the structure itself. Originally, towers were simple square-shapes, easy to build but also easy to topple down.

  One of the most ingenious ways that a tower was pulled down was a method known as undermining. An enemy's soldiers would dig a tunnel under one corner of a tower, prop it up with wood, and then set the wood on fire. When the wood burned to ashes, the tower would be so unstable (no longer having a good foundation) that it would tumble to the ground. However, sometimes undermining did not accomplish what the enemy soldiers wanted - sometimes the wood fell down before the enemy had left the tunnel, and they died! One of the towers at Rochester Castle near London still shows an unsuccessful attempt by an invader to pull down a corner tower.

  The round tower was determined to be a more effective shape for withstanding the impact of a battle. However, it was more difficult to build because the design was more complex. Yet, many castles made use of round towers. Their shape caused cannon balls and other types of missiles to bounce off the walls without doing damage. They also were not vulnerable to undermining. And they also gave an added bonus of providing more space on the interiors. The greatest of Norman knights, William Marshall, introduced the use of round towers to Britain, and they were especially used in Wales.

  Some castles used what is known as a splayed plinth, which added support at the base of the towers. The plinth had the effect of placing sturdy legs into the earth at the base of the tower, so that it would not lean or be likely to fall down. Goodrich Castle has excellent examples of the splayed plinth.

• The curtain wall (the wall which surrounded the main portion of the castle) gradually became a more and more effective means to stabilize the castle. At first, they were just simple walls, but with time, they became much thicker. The curtain wall was intersected at various points (good for observing the activity outside the castle, and to watch for invaders) by different types of towers, most of which were used for observation, but also as living quarters, the chapel, for storage, or to house the dungeon.

• One of the most important modifications to the curtain wall was the development of the gatehouse. At first, the gatehouse was just the way in and out of the castle, and was usually a simple doorway. However, they soon became the strong point of many castles, the place where an enemy was most likely to try to break through, so the gatehouses were equipped with several defensive techniques to thwart an enemy's attack. These included: the portcullis (a heavy iron grate that was lowered to block the intruder's entrance); heavy wooden doors that could be barred shut; strategically-placed arrowslits (slits in the stone wall that pointed outward, and through which a soldier could shoot arrows at an enemy without being shot back at); and murder holes (gaps in the ceiling above the entrance passage through which boiling liquids or deadly missiles could be thrown down upon attackers). One of the most complex gatehouses can be found at Pembroke Castle in Wales.

• Immediately outside the castle were other features which added to its stability. Most were surrounded by some form of ditch (which we more commonly called the moat). Ditches were deep, cut into the bedrock or earth around the main part of the castle, and also around a bailey. While many ditches were water-filled (some by changing the direction of an adjacent river!), others never had water. They were every bit as difficult to cross as the water-filled moats, because they were very deep and had very steep walls.

• In order to gain entry to the castle, wooden drawbridges were built to span the ditches. These bridges were ingeniously designed and could be moved away from the ditch to prevent unwanted visitors from gaining access to the castle. (By the way, inside the castles, entry to some of the towers, especially the keep, was by using a wooden ladder that reached the second floor, and could be removed to prevent unwanted access!)

  Sometimes more than one ditch and drawbridge were constructed, to make unwelcome access even more improbable. And many castles were built atop steep hillsides that would make it difficult for an invader to climb (especially carrying heavy weapons). These high locations also allowed the castle guards to see a long distance into the countryside, which was useful for detecting an invasion.