I came across some interesting discussion about new evidence for Late Roman legion size and composition on SOA forum. I will post some interesting bits if it is not accessible to all...

http://soa.org.uk/sm/index.php?topic=1809.msg20792#msg20792

“I think this is actually our first direct period source for the strength of a legion in the Late Empire: the literary sources offer only circumstantial data from which legion establishments have been inferred (and then, as is often the habit, downgraded from there).

This information does suggest that the new Constantine-and-after smaller legion was approximately one third of the size of a traditional legion as per Caesar to Vegetius. The old legion with an assumed 9 x 480-man and 1 x 800-man cohorts and an overall infantry strength of 5,120 seems to have been divided into three new legions, each with a theoretical ceiling of 1,706 men (1/3 of 5,120).

Guessing at the new legion establishment, it would seem logical to base it on the likely three- to four-cohort frontage of the old legion, say around 200 yards, but have it deployed in one line instead of the traditional three. Second and any subsequent lines would consist of other units, either legions or auxilia, allowing greater flexibility on the battlefield - at least in theory - because the second and third lines would not be tied to the first but could nevertheless support it.

Hence one might expect in the new legion:

- Three 480-man cohorts (1,440 men)

- One numerus of lanciarii or missile types (240 men?)

This would give a total strength of c.1,680(?) at full establishment. The three-cohort composition would allow a three-line deployment if desired, or the unit could be deployed in a single line (as appears to have been the case at, for example, Argentoratum).

One may note how the above suggested composition of the new legion appears to coincide with the strengths of 1,440 and 1,660 in the Perge fragments.”

From Patrick Waterson

Interesting book and going cheap on Oxbow:

https://www.oxbowbooks.com/oxbow/roman-military-architecture-on-the-frontiers.html

Table of Contents

List of Figures

List of Tables

List of Contributors

Acknowledgements

List of Abbreviations

1. Introduction:

Rob Collins and Meike Weber

2. Making sense of the frontier armies in late antiquity: An historian’s perspective

Conor Whately

3. Economic reduction or military reorganization? Granary demolition and conversion in later 4th century northern Britannia

Rob Collins

4. The 4th century and beyond: The Roman barrack at Binchester (Co. Durham)

David Petts

5. Fourth-century fortlets in Britain: sophisticated systems or desperate measures?

Matthew Symonds

6. The late Roman coastal fort of Oudenburg (Belgium): Spatial and functional transformations within the fort walls

Sofie Vanhoutte

7. The legionary fortress of Vindobona (Vienna, Austria): Change in function and design in the late Roman period

Martin Mosser

8. The dwindling legion: Architectural and administrational changes in Novae (Moesia inferior) on the threshold of late antiquity

Martin Lemke

9. Severan Castra, Tetrarchic Quadriburgia, Justinian Coenobia, and Ghassanid Diyarat: Patterns of Transformation of limes Arabicus Forts during late antiquity

Ignacio Arce

10. Castra or centenaria? Interpreting the later forts of the North African frontier

Alan Rushworth

11. In defence of the late empire

David Breeze

Some nice painting here:

https://jacksarge.blogspot.com/2019/07/late-romans-sub-romans-even-eastern.html" target="_blank">https://jacksarge.blogspot.com/2019/07/late-romans-sub-romans-even-eastern.html

Good stuff from Guy Halsall about Late Roman armies:

“It is generally thought that there was little real difference between ‘Roman’ and ‘barbarian’ forces in the fifth-century West. This is undoubtedly correct but I will argue that, rather than being resulting from the recruitment of large numbers of ‘tribal’ non-Romans, this was principally because ‘barbarian’ forces were, in effect, late Roman armies“

https://darkagewargaming.wordpress.com/2011/09/22/301/