15 Defining Parts of a Castle

The Normans built the first proper castles after the invasion of 1066. They needed bases from where they could patrol the countryside and strongholds to protect themselves from Saxon attack. They had to be built in a hurry, so they were made of timber and placed on top of an earth mound called a Motte. Basically a walled enclosure on top of a usually man-made hill.

Castles were built in strategic positions and where possible natural defenses were utilized such as hills, rocky outcrops, and rivers. The best place for a castle is on a hill, the higher up a castle, the better defensive advantage, but you can't have a castle without a well otherwise the enemy could poison your water supply.

A Bailey was the name given to the courtyard area within the castle walls. While the Lord's residence was in the Keep, the barracks, stables, blacksmith, etc., was in the Bailey. The majority of castles had at least one Bailey.

Since attackers could easily set fire to a timber-keep, they were quickly replaced with stone, but the earth on top of the Motte often couldn't take the weight. So they built the keep in the Bailey instead. The Keep would have been the strongest part of a castle with the thickest walls, the ground floor wouldn't have had any windows, and a single flight of stairs or steps would have led to the entrance on the first floor.

It wasn't very comfortable living in the keep. So eventually, the Lords moved out into proper houses in the Bailey; this meant that they weren't so well protected, so another line of defense was added known as the curtain wall. This new wall enclosed the Baily and had to be high and thick.

Often the curtain wall had a slope called the talus. Against this, the enemy couldn't reach the wall with a siege tower because the ramp of a tower wasn't long enough. It also provided a strong foundation to help support the wall against undermining.

Perhaps the most familiar castle design element is the battlements, regular gaps in the parapet (i.e., a small defensive wall between chest-height and head-height) along the top of outer walls, allowing for archers to fire down at an enemy then step aside for full protection.

Projecting towers were regularly spaced along the outer walls. They maximized the view of the countryside, allowing lookouts to spot invading forces easily. They had a weakness though. If you want to make a building collapse by tunneling underneath it or hurling boulders at it with a trebuchet, the best place to start is at the corner. So eventually the square edges were removed using polygons or by making the towers round.

Arrow slits were narrow vertical holes in a defensive wall that allowed firing arrows or bolts at attackers. The primary purpose of arrow slits was to protect the defender by turning him into a small target, but if the size of the opening was too small, it could also obstruct the defender so sometimes, a second horizontal opening was added to give an archer a better view for aiming.

Gaps in the floor called Machicolations formed a continuous corbelling over the entire enclosure (tower, curtain wall, etc.) which were used to drop stones or to pour boiling liquids onto the attackers at the foot of the wall.

Around the whole thing, there was a ditch or moat, of course, many castles couldn't have a water-filled moat because they didn't have a nearby lake or river. The moat made it incredibly harder for attackers to approach the castle and restricted the ability to get siege engines to the walls. Water moats also helped to prevent undermining since the tunnels could easily flood.

Since most castles were surrounded by a moat, people had to use a bridge to cross. In late medieval times, the bridge was constructed from large wooden planks attached to chains that were used to lower the bridge to let people in and raise it to keep attackers out.

The weakest point of any castle is the main gate. So you needed a gatehouse with one or more metal-reinforced wooden gates, known as a portcullis, and by the thirteenth and fourteenth centuries, the gatehouse developed a second outer gate or Barbican, adding yet further defense.

The attackers that make it past the killing field to the main entrance are then doused with boiling water, and quicklime poured from an opening above the gatehouse known as murder holes.

Even if they break through the entrance to the keep, attackers face narrow corridors and winding staircases that spiral up clockwise giving added sword room to the defenders. Also, the steps on the staircase were built unevenly making it difficult for attackers to climb and fight.