Spur castle

A spur castle is a type of medieval fortification that uses its location as a defensive feature. The name refers to the location on a spur projecting from a hill. Ideally, a spur castle would be defended on three sides by steep hillsides, with the only vulnerable side the one where the spur joins the next hill.

Depending on the local topography, a spur castle may depend mostly on its inaccessible location, or combine it with defensive features such as walls and towers. A typical feature is a neck ditch cutting off the spur from the rest of the hill. When the spur is long and narrow, the term ridge castle is sometimes used as well. A long spur castle is sometimes, but not always, subdivided into a lower ward and a more strongly defended upper ward (or even a succession of three or more wards).

Spur and hilltop castles were introduced by the Franks in order to hinder the deployment of the increasing use of the counterweight trebuchet. In the case of spur castles, heavy siege machinery could only be deployed on the uphill side enabling defensive works and forces to be concentrated there.

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