Late Roman Unit Sizes

[Nathan Ross]

Do these numbers ring any bell to anyone?

I'm afraid not - they do sound rather Greek or Hellenistic...

a document that seems to equate a legion with 1000 soldiers... under Diocletian, so this legion might refer to that period.

The number seems about right for that era, anyway.

On a similar note, I thought I might just float a theory about the development of legions and their constituent subunits:

Theory: In the later third century, imperial campaign armies were commonly assembled from two-cohort detachments (vexillations) of frontier legions. These were traditional cohorts, with 6 centuries of 80 men each, totalling 480 men excluding officers and ncos. The double-cohort vexillation would be 960 men (or close to 1000 including officers). The commander was a centurion given temporary rank as Praepositus.

At some point, perhaps under Diocletian or early in the reign of Constantine, these mobile vexillations were reconstituted into new 'mini legions', distinct from their parent formations. The two cohorts were combined into one large unit, which was then newly divided into 10 subunits - copying the arrangement of the traditional legion into 10 cohorts. These subunits would each be 96 men, led by centurion-grade officers, now called centuriones ordinarii, or just ordinarii. The subunits were perhaps still called centuries, but could have been renamed ordines, or perhaps cohorts (i.e. 'mini-cohorts', as this is a 'mini-legion'), which might explain why Vegetius says that each 'cohort' had a draco standard.

The commander of this new-style legion gained the official rank of Tribune (though sometimes still called Praepositus). Legion strength was still 960 men; with officers and others it would be around 1000.

Later, probably still in the reign of Constantine or his sons, extra men were added to the command of the ordinarii. These were senior soldier grades, first Flaviales, then (perhaps at the same time, or soon afterwards) Augustales. These ranks are unknown before the very late 4th century, but the names suggest they date from the Constantinian dynasty.

These extra men (20 per subunit) bring the size of each 'ordo' or 'cohort' up to 116 men, and the total strength of the legion to 1160, or 1172 inclusive of officers. This could have been rounded up to c.1200 in historical literature.

This later enlarged legion may have been the basis of the unit described in the Perge tablets, from the end of the 5th century. Legions on campaign may have operated with fewer 'cohorts', or with reduced men in each subunit, which perhaps explains some of the varying sizes given in our sources.

All very hypothetical - but does it sound valid?