CAVALIER, in fortification, an elevation of earth of different shapes, situated ordinarily in the gorge of a bastion, bordered with a parapet, and cut into more or less embrasures, according to the capacity of the cavalier. Cavaliers are a double defence for the faces of the opposite bastion: they defend the ditch, break the besiegers galleries, command the traverses in dry moats, scour the salient angle of the counterscarp, where the besiegers have their counter batteries, and ensilage the enemy's trenches, or oblige them to multiply their parallels: they are likewise very serviceable in defending the breach and the retrenchments of the besieged, and can very much incommodate the intrenchments which the enemy make, being lodged in the bastion.