Late Roman Army - seniores and iuniores

[nikgaukroger]

theory on the seniores/iuniores really has to include the auxilia in some way IMO

Yes, that is the difficult bit. But it occurs to me that this theory is quite similar to the idea of battalions, used in British and other armies in the 18th-19th century. The seniores would be the first battalion, and the iuniores the second battalion. The hierarchy would be determined by when they were first formed into an independent unit. Of course, it would be logical to call them (for example) Primi Herculiani and Secunda Herculiani, but that would lead to a confusion with the original legion numbering system, (especially if both were formed from detachments of Legio II Herculia!), which was still in use throughout this period.

So the auxilia could also have had a 'second battalion' raised at some point, also named iuniores to accord with the style used in the field army legions.

I still prefer it to the idea of all the units being split in half, or cadres being split off from each.

I too dislike the idea of the units being split in half, although the cadre idea I have little issue with and may be more likely for the auxilia palatina who have no "parent" body to be split off from in the way the old legiones do.