The previous discussion of the methods by which the auxilia were recruited has dealt only with the private soldiers, and, as a natural corollary, with such officers as were promoted from the ranks. To the position of _praefectus_, however, the private soldier could not normally aspire, and he attained it, if at all, only under exceptionally favourable circumstances.[283] Normally, the commanding officers of the auxiliary regiments were drawn from an entirely different social stratum to the men, and although the method of their appointment varied and the area from which they were drawn shifted its boundaries at different periods, these changes did not follow the same lines as those which we have been tracing in connexion with the recruiting of the rank and file. The auxiliary commands are familiar to all students of the Roman Empire from inscriptions of men who went through the equestrian career, the first stage of which was formed by the posts of _praefectus cohortis_, _tribunus legionis_, and _praefectus alae_. It has, however, been pointed out by von Domaszewski[284] that this system was not established until the middle of the first century. Under Augustus and Tiberius, not only was the relative rank of these posts still undetermined, but they were filled in many cases not by young men beginning the equestrian _cursus_, but by veteran centurions from the legions, especially the _primipili_. We have noticed this system in the army of Caesar, so that here, as elsewhere, Augustus was continuing a republican practice. The following inscriptions,[285] which are both of early date, give typical careers of this character. 1. C. Pompullius C. f. Hor(atia) prim(us) pil(us), trib(unus) mil(itum), praef(ectus) eq(uitum). 2. M. Vergilio M. f. Ter(etina) Gallo Lusio prim(o) pil(o) leg(ionis) XI, praef(ecto) coh(ortis) Ubiorum peditum et equitum, donato hastis puris duabus et coronis aureis ab Divo Augusto et Ti: Caesare Augusto, &c.