The cuneus is usually thought of as a close formation for breaking through enemy lines (Livy 7.24; Caesar, Gallic War 6.40).
The literal is ‘wedge' and so a sharp triangular formation might be envisaged, but it was also the term applied to a keystone. According to Vegetius, the late Roman military theorist, the formation was narrower at the front than at the rear and known in military slang as the ‘pig's head'. The counter-formation deployed against it was the (forceps) (Vegetius 1.26, 3.17–19; compare Ammianus Marcellinus 17.3.9).
