Late Roman Unit Sizes

[Frank]

Although I would prefer to see it move down to the level of a legion vexillation - this, rather than the auxiliary cohort, had been the central tactical element of most Roman field armies since the Marcomannic wars, it would appear. While we do have vexillations of combined aux cohorts, I suspect they were still largely used in a support role.

Possibly.

But vexillatio has several meanings. Basically it is just any detachment of soldiers from different units or just from one unit, e.g. 20 soldiers deployed to help repairing a street or 12 cohorts from 3 legions (all heavy infantry) marching from Moesia to Syria.

But I guess you refer to the tactical vexillatio. For me, that is nothing else than a fully operational and balanced small exercitus composed of all needed unit types: e.g. 2 cohors legionis (heavy infantry), 1 auxilia cohort (light infantry), 4 turmae and 2 centuria of archers under command of a tribune. Well, not all unit-types are always needed. Depends on the enemy.

There are hints, that the late roman units became much more flexible, than the units of the principate. So some units might have been a mix of heavy and light infantry. And some legionaries were even decent archers or slingers. So perhaps the new legion was not purely heavy infantry anymore. Even if specialized units did still exist in the field-armies.

If the late roman legion emerged from vexillationes or the core of stripped off legions, than it is hard to say, how strong they were at the end. Could be anything between 1 cohort and 9 cohorts.
But 800 (just the 1st cohort remaining) and 1000 ( the typical 2 cohort vexillatio per legion) sounds reasonable. The mother of all questions is: Did the romans ever define a new standard for the paper strength of a legion? Perhaps for the comitatenses and palatini, but for the limitanei?

Perhaps a limitanei units paper strength was just, what was rest after all these losses by vexillationes or what was available, when the new limitanei unit was founded anywhere. In this case, at least the late roman border army might look like a big mess. And it is senseless to look for standard unit sizes.