Centurion Rank

[Renatus]

I have thought about this in relation to Vegetius’ inclusion of both a centurio primi pili (i.e., primus pilus) and a triarius prior in his First Cohort. At first sight, since pilani and triarii are synonymous, this seems to place two senior centurions in the same cohort and, as triarius prior is a rank otherwise unattested, the reference is generally thought to be an error. On the other hand, I have long held that Vegetius is, generally speaking, an honest reporter of his sources and, as he shows no indication of having known that centurions could be designated prior or posterior, there is the possibility that he found a reference to a triarius prior in a source now lost to us. Livy, in dealing with the army of the mid-fourth century BC, states that the senior centurion, primus pilus in his day but then called primus centurio (7.41), was placed in battle “inter triarios” (8.8.16), without saying in terms that he led or commanded the triarii. This opens the possibility that the primus centurio might have been supernumerary to a triarius prior who actually commanded the first vexillum of the triarii.