A medieval castle moat was a deep and wide ditch surrounding medieval castles for the purpose of defence. The ditch was commonly filled with water and thus acted as one of the primary castle parts for protection against enemy invasion. Dry moats also provided excellent defense and were often filled with spikes or other obstacles.
Natural moats were much wider and deeper than man-made moats which were usually around 12 feet wide and 30 feet deep.
Preliminary forms of ditches surrounding castles and towns were found in ancient civilisations of Assyria and Egypt. However, more elaborate forms of ditches known as medieval castle moats became increasingly common during the high and late medieval periods.
The most important purpose of a medieval castle was defence. A moat around the castle made it difficult to approach the castle walls with ladders and siege weapons such as battering rams and siege towers.
Further, medieval castle moats also served as an important deterrent against the practice of digging tunnels (mining) under the castle walls to either penetrate the castle or collapse the castle walls.
There were several kinds of castle moats including cross ditches that separated different parts of the castle and neck ditches which were dry moats.
A castle moat had supreme importance in the castle parts for preliminary defence. The first requirement to make a castle moat was access to a water source. Due to this reason, it was common to build castles near a water source such as a river, stream, or lake. A special dam was constructed in order to channel the flow of water into the medieval castle moat. The depth of a medieval castle moat could be up to 30 feet while it could be as wide as 12 feet.
Castle parts reserved for defence were of primary importance during the medieval times and therefore special attention was paid to the construction of effective medieval castle moats. A medieval castle moat served several defence purposes.
The obvious purpose was to make the approach of the heavy siege weapons difficult. Some weapons such as siege towers needed to be brought near the castle walls to work effectively and a medieval castle moat acted as an effective deterrence against such weapons. Further, a medieval castle moat precluded the danger of tunneling underneath the castle walls which was an effective method of penetrating the castle defenses.
There were various methods to overcome the medieval castle moat during an invasion. If the moat was dry, it could be filled with rocks, and other things until the ditch could be effectively crossed, however, this would be extremely difficult whilst being under fire from the castle’s archers and other troops.
Another way possible option was to sail a barge across the moat to the castle walls. In any case, it wasted a lot of time which the defenders of the castle could use to their advantage.