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 lordís 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 kingís 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 kingís 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 lordsí 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:
One of the most ingenious ways that a tower was pulled down was a method known as undermining. An enemyís 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.
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.