Types of Castles
This article takes a look at the various types of castles that were built. There are of course many different types but they can be readily broken down into a few easy to understand categories. For the most part it is reasonably easy to achieve this breakdown in castle types because they are something that changed over the course of centuries due to improvements in architecture, masonry, mathematics, and other skills. And, the builders of castles, because of centuries of experience, designed castles that were more effective.
An interesting aspect of the development and types of castles is how they were often transformed from one type into the next. A castle could almost be like a living thing where an early motte and bailey site was torn down and a keep was built on it. Then in later centuries it would be expanded into a shell keep and even later it could be further improved and developed into a concentric type castle. And, when the usefulness as protection was outlived because of modernized warfare some were even transformed into pure living quarters for royalty.
In this article I will show you the major types of castles in the context of how they came about in a rough time line.
Motte and Bailey Castle - This type of castle isn't what we typically think of when we think "castle" but the Motte and Bailey is the first type of European castle. They are considered to be the beginnings of the great castle age. These were prolific between the 10th and 12th centuries. And it is believed that there were as many as 500 of them just in Great Britain.
About the Motte and Bailey: A Motte is a mound of dirt and a Bailey is a courtyard surrounded by a wall or a fence.
The Construction of a Motte and Bailey: Two circular ditches were dug one smaller and one larger. And the soil removed from the ditches was used to build up the Motte and to form a berm around the ditches. Then a stockade fence and a keep were built.
You can see by the drawing that there were many similarities to castles that would come in later times. Good examples of this are the keep, the surrounding fence (which in later castles were stone), the Bridges and the gatehouse.
The Rectangular Keep ( also called a donjon or dungeon) 11th and 12th Centuries
The Rectangular Keep was the early types of castles that we are more familiar with today. They were built of stone and tended to have very high and thick walls. They were an improvement in stone on the Motte and Bailey. But generally they couldn't be constructed on top of a motte because of the tremendous weight of the stone. A couple of interesting design note about these towers was that often the only entrance into it was actually up on the second floor which made it more difficult for enemies to gain entrance. And they were often surrounded by some kind of a curtain wall like the bailey was. Except the curtain wall was stone. The most famous example of the Keep is the Tower of London.
The Shell Keep 13th Century
The Basic structure of a Shell keep was a circular or semi-circular shell of stone wall with various buildings inside it. Sometimes a Motte and Bailey was upgraded into a stone shell keep. The Stockade fence around the keep would be replaced with a stone wall. Restormel Castle in England is a fine example of this type of castle.
The Concentric Castle 13th - 14th Centuries
This type of castle is a combination of the shell keep and the rectangular keep. It is an expression of a very important technique in defense - that of concentric lines of defense. In effect it is a keep surrounded by a wall which in turn is surrounded by another wall. Sometimes there were moats in between these concentric circles or on the very outside. These moats are in themselves further concentric lines of defense.
This series of defenses was a very effective means of protection because attackers had to break through each line of defense one at a time. If a line of defense were penetrated by an attacking army the defenders could retreat to the next inner defense and the attackers would have to start anew against this new line. These lines of defense finished at the center of the grounds with the keep.
Some other important developments in castles were the change from very square blocky buildings to round buildings (particularly towers) Round towers were much stronger and able to resist attack better and a defender looking out the window of a round tower was able to see more. The square towers caused angles that formed blind spots that attackers could hide in.
This illustration of Harlech Castle shows three separate concentric cirlces. Each area that they encompass are called Wards. So it has an inner ward, a middle ward, and an outer ward. Part of the defense of the outer ward is a moat.
The Palace or Royal Quarters - 14th -16th Centuries
Technically we could be blurring the line a little bit when we talk about palaces and living quarters as being castles. But they were a natural extension of the traditional fortress castle and many of the fortress style castles were transformed and upgraded into palaces and living quarters.
As weapons (particularly gunpowder weapons like the cannon) grew better, more powerful and more accurate the castle fortress became less and less effective. It could take years or even decades to build a stone fortress castle and it was now possible to totally destroy it in a few days with steady cannon fire.
This ended the building of castles as fortresses but, the building and architectural techniques were still used to build large structures. The focus now was less on defense and more on lavish living quarters or centers for governing. And many Fortresses that were still standing were also re habilitated and re purposed as living quarters.
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