Curtain wall (fortification)

Lore & Background

In medieval castles, the area surrounded by a curtain wall, with or without towers, is called the bailey. The outermost walls with their integrated bastions and wall towers together form the enceinte, the main defensive line enclosing the site. Curtain walls were often built to considerable height and fronted by a ditch or moat to hinder assault. Walls were topped with battlements consisting of a parapet, generally crenellated with merlons to protect defenders and lower crenels or embrasures for shooting; merlons were sometimes pierced by loopholes or arrowslits. Behind the parapet was a wall walk for defenders to move or fight. Larger curtain walls had mural passages or galleries built into the wall thickness with arrowslits. Some walls had projecting wooden platforms called hoardings or brattices, and stone machicolations performed a similar function.

Reader's Guide

The curtain wall was a fundamental element of defensive architecture from ancient times through the medieval period. Its design evolved to counter siege tactics: high walls with battlements, moats, and projecting platforms allowed defenders to repel attackers. The introduction of gunpowder and heavy cannon in the early modern period made tall curtain walls vulnerable, prompting the trace italienne style from the 16th century. In these fortifications, curtain wall height was reduced, and additional outworks such as ravelins and tenailles were added beyond the ditch to protect the walls from direct cannon fire. The curtain wall's legacy is seen in its influence on later fortification designs and its enduring presence in historical sites across Europe and the Middle East.

Did You Know?

• Evidence for curtain walls appears in historical sources from Assyria and Egypt.
• The early 5th century Theodosian Walls of Constantinople influenced medieval castle builders.
• The introduction of gunpowder led to the trace italienne style, reducing curtain wall height.