Extract

Praefectus means ‘placed in charge’ and describes a great variety of men set in authority—officers in the army and navy, major imperial officials, judicial officers delegated by the praetor (see praefectura) and deputies for local magistrates.Before the *Social War (3) each wing (ala) of allied cavalry had six praefecti, three of whom were Roman officers. In *Caesar's time cavalry continued to be commanded by praefecti, while the praefectus fabrum (chief of engineers), e.g. Caesar's officer *Mamurra, became an aide-de-camp to the commander. Under the Principate units of allied troops (*auxilia), both wings of cavalry and cohorts of infantry, were commanded by praefecti, who were of equestrian rank (see equites). The administrative post of legionary camp commandant, praefectus castrorum, was from *Claudius' reign onwards regularly held by an ex-centurion who had reached the rank of primus pilus (see primipilus) but was unlikely to have further promotion.