What is a Medieval Castle Moat?

A medieval castle moat was a defensive structure that formed a critical part of the castle’s defenses. Most medieval castles were built as key military fortifications. In defending such castles from an attacker, a moat was one of the most effective defenses.

The moat was essentially a large and deep ditch that was dug all around the castle’s boundary walls. The ditch was then either filled up with water or if it was to be a dry moat it had wooden stakes erected all over it. This essentially secured the walls of a castle from being accessible to an attacker.

A Trebuchet Catapult Siege Attack on a Castle


Castle Moat *Structure

A medieval castle moat comprised of a fairly wide and significantly deep ditch that ran all along the boundary of a castle. The width of the moat could reach as much as 12 feet while its depth could be as much as 30 feet. It was for the purpose of constructing an effective moat that medieval castles were often built near a water body such as a river. Water from such a body was then transported to the moat.

Medieval Castles Defences Moat

Access from the castle to the outside world was made possible by a narrow and heavily guarded drawbridge which was lowered and raised as needed over the castle moat.

Portcullis Drawbridge Counterweight

The Portcullis used as a Counterweight for the Drawbridge

In some cases, the castle defenders would choose to use wooden stakes in a ditch rather than filling it with water. Such a moat was still formidable in stopping the advance of an attacking army.


Purpose of a Castle Moat

The purpose of a medieval castle moat was purely defensive. It was aimed as a primary barrier to an enemy’s advance on the castle walls. When filled with water, the moat made it impossible for a regular army to march onto the castle’s boundary walls.

Windsor Castle Arrow Slit

Interior View of Arrow Slit *Windsor Castle

Rather, the attackers then had to wade through water which made them highly vulnerable to the defenders on castle walls. Similarly, if the moat was set up with wooden stakes, it became virtually impossible for cavalry to approach the walls safely.

Cataphract Cavalry Soldier

Rather, the horses and men had to make their way through the dangerous stakes at an exceptionally slow speed. This slow speed gave the castle defending archers an opportunity to launch their missiles and pick out the attackers.

Medieval archer using longbow

In such a way, the moat served the vital purpose of being a very solid defense against an outsider attacker.


Castle Moat Defence *Decline

Rudimentary types of castle moats were already being used by the Normans when they arrived in England in 1066. These were frequently used when the Normans built their motte-and-bailey castles. These early types of moats eventually gave way to the development and evolution of the later medieval castle moats.

Such medieval moats became particularly popular in England during the period of Plantagenet kings. This period, which lasted from the mid-12th century to the late 15th century, saw the construction of many iconic medieval castles.

Since these castles were primarily constructed for military purposes, many of them made effective use of moats. The efficacy of a moat in a castle’s defenses subsequently declined once gunpowder weapons became more widespread.