Spur castle

A spur castle is a medieval fortification built on a projecting ridge of a hill or mountain. Its ideal position leaves three sides protected by steep slopes, leaving only the side where the spur connects to the main hill vulnerable to attack. This distinguishes it from a ridge castle, which has steep terrain on just two sides.

As a type of hill castle, a spur castle might rely entirely on its difficult location or incorporate additional defenses like shield walls and towers. Builders sometimes carved into the natural slopes to make them steeper and prevent landslides. A common feature is a neck ditch that separates the spur from the rest of the hill. Longer spur castles are often divided into a lower ward and a more heavily defended upper ward, sometimes with three or more sections.

The Franks built and improved high spur and hilltop castles to counter the growing use of the counterweight trebuchet. For a spur castle, heavy siege equipment could only be positioned on the uphill side, allowing defenders to concentrate their forces and fortifications there.

Examples include the crusader castle Krak des Chevaliers in Syria, which sits on a spur accessible from the south but has strong concentric defenses on all sides. The Citadel of Salah Ed-Din in western Syria focuses its defenses on the spur’s vulnerable side, especially a deep ditch, while its lower bailey has weaker walls and towers. Alamut Castle in Persia (northwestern Iran) stood on a narrow rock base rising about 180 meters and was considered impossible to assault directly. The Alcázar of Segovia in central Spain occupies a narrow spur with steep drops on all sides except the east, where level ground provides access. Stirling Castle in Scotland is on a narrow spur with drops on three sides and a gentle slope from the south-east. Château de Chinon in central France, used by the counts of Anjou in the 12th century, was captured by the French king in 1205 and became the largest castle in the Loire valley. Poenari Castle in Romania sits on a cliff 440 meters above the Argeș River and served as Vlad the Impaler’s fortress. Château de Montségur in France, used by the Cathars, lies on a mountain spur. Cefnllys Castle in Wales consists of two castles on a spur.