Cohorts, Cavalry and Whatever Goes

[D B Campbell]

Duncan Campbell has made the claim “The Polybian legion cannot be compared in any detail with the imperial legion…The two are very different, particularly in the make-up of the cavalry component. Polybius' legionary cavalry are provided by the Roman gentry ("equestrians"), and are quite separate from the infantry levy.” Mr Campbell has not provided any evidence to show that the cavalry of the Polybian legion are not included in the same century as the infantry, and his conclusion is misguided.

When you say that I did not "provide any evidence to show that the cavalry of the Polybian legion are not included in the same century as the infantry", obviously you are correct, because the Polybian legion has no centuries! However, I would venture to suggest that it is your conclusion that is misguided.

You seem to be implying that the infantry and cavalry were allocated from the same general levy, in a proportion of your choosing, whereas the point that I actually made was that the legionary cavalry came from a different source entirely (namely, the equestrian nobility), so it was fundamentally separate from the make-up of Polybius' legion.

I'm sure most of us are familiar with Polybius' famous description of the Roman military system in Book 6 of his Histories. I would have thought that his explicit statements, (a) that the cavalry are chosen before the infantry, and (b) that they are selected according to their wealth, are sufficient to show that they are not numbered amongst the infantry levy (Polyb., Histories 6.20.9). Polybius goes on to describe how the legion is mustered (6.22.6-10), but -- naturally -- they are all infantrymen. The cavalry are organized separately (6.25.1-2).

This is, of course, fundamentally different from the system that prevailed during the period of the empire, when admission to the legionary cavalry was treated as a promotion for an infantryman. That's about as different as an apple is from an orange.