Late Roman Unit Sizes

[Nathan Ross]

the process for the creation of iuniores units - a smaller part detached from a parent unit and being enlarged afterwards.

Oh, I suppose so, yes. But I suspect it was a different, if similar, process.

how would you propose those detachment were named? And wouldn't we see that somehow in any records?

I would suggest the process went something like this:

In the late 3rd century, Legion I Italica, based at Novae in Moesia, sends a two-cohort vexillation to join the imperial army on campaign (in North Africa under Maximian, for example).

Returning from campaign, this detachment is stationed in Aquileia, and takes the name Prima Italica Moesiacae (CIL V, 914) - at this point it's still a 12-century 960-man legion detachment, but already operating independently.

At some point - maybe c.AD300, the two-cohort detachment is reconstituted as a 960 (or 1000) man 'mini-legion'. It is now known officially as the Moesiaci.

At some later point still, the Moesiaci unit is either divided or duplicated (from a cadre of the older unit, perhaps), or a new detachment taken from the parent Legion I Italica and also called Moesiaci - the two different units are renamed Moesiaci Seniores and Moesiaci Iuniores respectively, to distinguish them.

Some time prior to the compilation of the Notitia Dignitatum, however, the Moesiaci Iuniores is either destroyed or disbanded. The senior unit maintains the name.

But all of this process is (as we all know) pretty obscure!