Cavalry Cohorts

[Nathan Ross]

Ammianus 16,11,6 and 16,12,39 and 18,6,16 and 21,6,6 and 21,11,2 and 24,3,1 states that turma are commanded by a tribunus.

Yes, I noticed that in your last set of references. It is very strange - traditionally, of course, quingenary auxiliary cohorts were commanded by praefects, while tribunes commanded only the milliary ones. A turma was around 30 men, so certainly not a tribune's command! Whatever does Ammianus mean by this?

In the ND, it does seem that the limitanei cohorts (like the field army legions, equites, scholae and auxilia) are now led by tribunes. Praefecti command the limitanei legions, the alae and the numeri of 'milites'.

So 'tribune' seems to have become a rather variable sort of rank. Even so, having one command a 30-man turma (traditionally a decurion's role) seems a bit much.

I wonder, actually, whether the commanders of all these units were more usually called praepositii (this seems the most common designation in inscriptions), and 'tribune' was a sort of courtesy title, perhaps?

Turmae seem to have fallen out of use by the 4th century anyway - I'm not aware of any contemporary references to them outside Amm; do you know of any? - so maybe a bit like cohorts, in the field armies at least, this was an obsolete term used in a generic way.

Ammianus's 'grand style' I take to mean that he's writing in the manner of Tacitus. So perhaps he's using words like cohort and turma (and maniple, and Parthians!) because Tacitus did? We should remember that Amm himself was a Greek ('and a soldier', as he tells us at the end), so while he's writing his history in Latin he may have been 'translating' more accurate contemporary military nomenclature that he was familiar with in Greek (arithmoi, etc) into slightly archaic Latin.