Late Roman Unit Sizes

[ValentinianVictrix]

Evan wrote:
Ultimately, this discussion has proved invaluable to my book, as I plan to present my theory on the 2400-man Legion in the chapter on the Roman Army.

At the moment I’m exploring 3000 man legions (1500 iuniores and 1500 seniores). The Romans don’t do things ad hoc and Julian’s army having to hand over bodies of 300 men tells me a mathematical ratio has to be in play. Besides playing with the numbers, it is important to try and understand Roman military doctrine for this period. Did the Romans attach one 500 man cohort of auxiliaries (archers?) to a legion, thereby increasing the iuniores and seniores from my theory of 1500 men to 2000 men? Taking into account Ammianus numbering 1000 archers accompanying the targeteers, this could be a possibility. However, we don’t know if the figure of 1000 archers is rounded down from 1200 archers or the figure is correct. Also could the Romans leave behind 300 men as garrison troops, thereby sending a force of 1200 iuniores or seniores into the field? What if of the 1500 men, 500 men are left behind as a garrison force? Now we have a legion of 1000 men. At present I believe I am building a better case for the 1500 man legion for the iuniores and seniores than the 2400 man legion.

Evan wrote:
Zozimus describes the Palatina units coming from Constantinople totalling 4000 men and would average 666 men a piece, not accounting for variations.

This is taken from an earlier post in this thread and I am curious as to where you got the figure of 4000 men from as Zosimus only gives 6000 men on two accounts.

Ammianus gives two accounts where numbers of men were detached specifically from each Legion, Gratian detached 500 men from each legion to go chasing the Lentienses up the mountains and then Valens allowed Sebastianus to detach 300 men from each legion. There is also a passage which I believe is in Lydus where he states that 1500 men from the Legiones Lanciarii and Mattiarii were involved in a tunnelling operation when Julian invaded Sassanid Persia. Its unclear whether it was 1500 men from each Legion or 1500 men in total, or 750 men from each legion. If it was 1500 men from each legion then obviously the Legiones were much larger than 1500, I would suggest even if it was 750 men detached from each legion then the legion size would have also been larger than 1500, probably around 2250 men.