Moats were an important part of a medieval castle’s defenses and were usually the earliest of the barriers that an attacking enemy had to face.
They proved formidable in that they made it impossible for the enemy to attack a castle using conventional methods such as scaling the walls, using battering rams, or tunneling.
Consequently, an attacker had to devise unconventional and often costly methods when storming a castle protected with a moat. It was certainly possible to overcome a castle moat but it was more time-consuming, incurred more losses in terms of dead soldiers, and was more vulnerable.
A moat effectively rendered nearly all conventional methods of attacking a castle redundant. Conventionally, the attacking army could use three ways of storming a castle.
Each method was used with varying success in conventional castle attacks. But if a castle was surrounded by a moat, all three methods proved futile.
Since the conventional method simply didn’t work on a castle protected by a moat, other ways had to be devised to overcome a castle moat.
If the castle was surrounded by a dry moat, the enemy forces would use wood, stone, and rocks to fill up the dry ditch. This took considerable time and had to be done under the cover of wooden shields in order to be safe from the attacks of castle defenders.
Once done, this allowed the attackers to carry scaling ladders and reach castle walls.
When faced with a moat filled with water, the attackers had to resort to other measures. They would build a makeshift bridge and then use it to reach castle walls. Alternatively, they would use barges to sail toward castle walls.
Both methods were quite hazardous and involved significant losses in terms of men due to the castles archers and other military attacks from the castle walls.
All the methods of overcoming a castle moat, as mentioned above, involved incurring significant losses. These losses were in terms of soldiers who were wounded or killed by the missiles from castle walls as they attempted to overcome the difficulties of the moat.
The losses were also in terms of the time lost in overcoming the moat which made it possible for a reliving force from outside to arrive and attack them from the rear.
Although fraught with difficulties and losses, these were the only ways of effecting a breach into a moat-protected castle. For these reasons, moats were highly preferred by the defenders of the castles.