Medieval castles were typically protected by high and thick walls, protective towers, and men on castle walls. An army attacking a castle had to undertake different tactics and use a wide variety of weapons.
The attacker would lay siege to a castle and wait for the inhabitants of the castle to starve to death or use siege weapons to launch an offensive attack and overwhelm the castle defenses.
Among the most notable siege weapons used in the medieval period were catapults, siege engines, ballista, battering rams, and siege towers.
Catapults were one of the most popular siege weapons used in the medieval period. Catapults were used to hurl huge stones into and above castle walls and gatehouses.
When faced with thick and impenetrable castle walls, an attacking army would use a catapult to launch large rocks against the walls. Such attacks could often bring down even a fairly strong curtain wall (outer wall).
Catapults were also used to throw a multitude of other things such as diseased human and animal corpses over castle walls in order to spread infections among the besieged castle inhabitants. Flammable projectiles were also launched using catapults to torch wooden structures inside the castle walls.
As an attacking army closed in on the gatehouse of a castle, a major barrier they faced was that of breaking an entry through the entrance. Later stone castles were built with a formidable gatehouse that was usually constructed very solidly and had defensive properties that made it very hard for the attackers to overcome.
If the was no outer moat the attackers could use a battering ram which was essentially a tree trunk that was commonly tipped with iron. The attackers would wield the ram on a swinging structure so that they could bring it with force against the gatehouse entrance repeatedly.
If the battering ram repeatedly struck a given place, it was able to penetrate the entrance and give the attackers a sufficient place to breach the castle’s defenses.
The ballistas was one of the oldest types of siege weapons used in Europe. The basic structure of a ballista enabled attackers to launch large projectiles over long distances. The target of the projectiles was usually the defenders on castle walls.
Attackers would launch spear-sized arrows directly into the ranks of the defenders. The velocity of these arrows was such that they were able to pierce the best of the defenders’ armours. The Ballista was very effective in taking a toll on the number of castle defenders and demoralizing the castle inhabitants.
Siege towers were among the most formidable type of medieval siege weapons. Siege towers are essentially comprised of a large wooden tower of a rectangular shape. The tower usually had four wheels to enable it to move. Once the attackers populated a siege tower and took positions inside to shield them from the hail of enemy arrows, the soldiers on the ground would push the siege tower near the castle walls.
The tower was usually designed to be at par with castle walls or even higher. This gave the attackers a great advantage as they inched toward castle walls on top of the siege tower. The top of a typical siege tower usually included a drawbridge which was lowered as soon as the siege tower neared castle walls. This drawbridge was then used by the attackers on the tower to make their way onto the castle walls.