Concentric Castles
It was a medieval arms race. Every time castles were built bigger or stronger, some creative medieval
warrior invented a new siege weapon to breach the castles' defenses. Soon, even stone castles weren't good
enough.
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There was no stronger material than stone for building castles, so castle architects looked at the design of the
castles instead. They found creative ways to make improvements, just as armorers had when they built weapons
like catapults and trebuchets. Their new and improved castles were called concentric castles. Some of the best
concentric castles were built under the direction of King Edward I in Wales. He had been victorious against the
Welsh and built a ring of concentric castles to hold on to his newly won power there.
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Building a concentric castle took lots of time and lots of money. In fact, some of the best ones, like King
Edward's castle, Beaumaris, in north Wales, were never finished. Even though it was never completed,
Beaumaris was a great defensive castle in its time, and it still stands today. It was a special castle because it was
built right next to a dock. Ships could sail into Beaumaris and deliver supplies even when the castle was under
siege.
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Concentric castles were not a completely new design. Rather, like many great ideas, they were an
improvement on an older design. Concentric castles were an improvement on the older stone keep castles and
the even older motte and bailey castles.
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Like the stone keep castle, a concentric castle was surrounded by a curtain wall, but the concentric castle
went even further. Concentric castles had two, or even more, curtain walls. This made them much more secure
because, if an attacker made it through the first wall, he was trapped between the two walls and became an easy
target for archers inside the castle.
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The innermost wall was always the highest so that defenders could keep an eye on what was happening.
Concentric castle walls enclosed a large area of land too. The baileys inside the castle walls were large
enough to house many people and to hold large stores of supplies. Some castles even had fields inside so that
the residents could grow their own food. Now that castles were so large, the residents could hold out longer
when the castle was under siege.
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Towers were spaced along the castle wall. Towers were built round now instead of square. This made them
less vulnerable to attack too. Without square corners, they were harder to undermine. The round shape also
resisted arrows and other missiles better than the old square shape. Some towers were built in the shape of
polygons with more than four sides for the same reasons, but the old square towers were a thing of the past.
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Castles were built with a large, heavily fortified gate house now too. Since the gate had always been a weak
area in a castle's defenses, this was a big improvement. The gatehouse, like the rest of the castle, was now built
with layers of defenses. Some gatehouses were intentionally built to let the attackers break through the first wall
easily in order to trap them inside.
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Concentric castles did not have a large central keep like older castles. The central keep had always been an
attacker's main target. Now, with the parts of the castle spread out over a large area, the enemy could not be so
sure just where they should aim their attack.
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Many concentric castles were still surrounded by a moat, like earlier castles. Many still had defensive
structures like a drawbridge or a portcullis, which was a gate that could be raised and lowered. Arrow slits and
murder holes still provided secure places for the castle defenders to fight back. So did crenellated walls.
Crenellated walls had that "castle shape" at the top edge where it looks like every other block is missing.
Concentric castles were a great improvement in castle defense, but in some ways there were just like the old
castles. Inside, they were dark and damp, smoky from the fire yet still chilly. Lords and ladies in the castles
certainly had it better than the peasants who lived in hovels outside the castle walls, but few of us would want to
change places with them today. Castles were not comfortable places to live in by modern standards, but they are
great places to visit or to read about.
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