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Castles & knights

Castle walls and battlements

The walls of Conwy Castle, WalesThe walls of Conwy Castle, WalesA castle's first line of defence was the high, thick, outer wall that completely surrounded it. The tops of the walls, the battlements, usually had a jagged design known as crenellation: a series of gaps that allowed the castle's defenders to fire arrows from the tops of the walls on to the enemy troops below while providing cover when they reloaded their bows. There were also narrow slits in the walls through which archers could fire their arrows while remaining protected from return fire.

Building the wallsBuilding the walls


The walls between towers were called curtain walls. They could measure between three to five metres (10–16 feet) in thickness. The inner and outer faces were constructed first. The stones were fitted carefully into place. The space in between was then filled in with rubble mixed in with mortar—a mixture of sand, lime and water. Some walls were constructed with arched passageways running inside the walls, to enable guards to get from one section another hidden from enemy view. The walls were then limewashed (painted white) to protect against the rain and to give a smart finish. 

The base of the wall, called the plinth or batter, was angled outwards. This design both made it harder for a siege army to undermine the walls, and increased the chances that any boulders dropped from the top of the walls would bounce off the plinth into the ranks of enemy soldiers below.

Side view of a castleSide view of a castle

Arrow loop and cross slitArrow loop and cross slit

Arrow loops

A baron held land granted to him by the king, but did not own it outright. Any lord seeking to build a castle was obliged to ask permission of the king. This was given in the form of a “licence to crenellate”. If the lord had built the castle without the licence, the king could have seized it from him.

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