Castle Moat – Origins, Construction and Defenses!

Medieval castles were typically military structures meant to secure a region for the lord. Since the lord himself usually resided within such a castle, the security of a medieval castle was a key concern. Among the vital defenses of such a castle was a moat. A moat was a deep and wide ditch surrounding the entire castle.

Sully Castle Moat and Tower

It was often filled with water or set up wooden stakes. A drawbridge was typically used to let people cross the moat to enter or leave the castle. In the case of an attack, the drawbridge was raised and the attacking force had to contend with the moat before getting near to the castle walls with siege weapons and towers.

Drawbridge to a Castle Gatehouse

Drawbridge Leads to the Castle Gatehouse Entrance

Castle Moat Origins

The medieval castle moat evolved from the early medieval motte-and-bailey castles in which the Normans excelled. After the 1066 Norman Conquest of England, the motte-and-bailey castles dotted the entirety of England as Norman attempted to cement their control over the newly conquered territories.

motte bailey wooden castles

In constructing such castles, the Normans would excavate earth and erect a steep mound with it, constructing the main keep or tower at the top of the mound. Due to the earth excavated for the mound, a ditch was created at the bottom of the mound which became a formidable defensive structure, often filled with water for additional defense.

Castle Moat Medieval Castle

The word moat thus evolved from the French ‘motte’ and by later medieval period, it began to refer exclusively to the defensive ditch around a castle.


Construction of a Medieval Castle Moat

A medieval castle moat was built for purely defensive purposes. The primary purpose was to keep the attackers away from the walls of a castle. To accomplish this, the moats were often made to be very wide and deep. Moats were larger when the castle was built on an island with a natural water source surounding it such as a lake.

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This expansive ditch was dug all around the castle’s external walls and was then filled with water or set up with wooden stakes. Any enemy attacking the castle then had to contend with the moat before gaining access to the castle walls.

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Defensive Use of Medieval Castle Moat

When filled with water, the moat was certain to stop the advance of an attacker. The attacking force then had to swim through the water which was a significant problem. As the enemy waded through the water, defenders on the castle walls could easily pick enemy soldiers with their arrows and other missiles and weaponry.

Medieval longbowmen medieval archers image

A moat also effectively barred the enemy from undertaking tunneling against the castle walls.

Miners could tunnel underneath a castles walls, this was a tactic that was often used in the medieval period, as miners dug under the curtain wall of the castle they would build wooden frame structures, which they would then set alight, the wood now holding up the section of the wall would weaken and in time it would give way and collapse the wall.

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