High Imperial Roman army vs Late Roman army

[Alexand96]

There are a number of points that need clearing up here.

The Late Roman army did not give up the use of the Pilum, only that it was rarely used as stated by Vegetius. It was being replaced by a thrusting spear called the Spiculum that could either be thrust to fend off cavalry or thrown and had the same shield and armour penetrating power of the pilum it was replacing. There is some evidence in Ammianus that the pilum was being used as late as the 360's/370's as he several times states troops were throwing 'pilis' during the reigns of Valentinian I and Valens (Valentinian was stated by Ammianus as being an 'inventor of arms' and may have reintroduced the pilum as well as other more exotic weapons such as the Currus Drepanus).

From my own research, using actual numbers of infantry and cavalry from sources, indicates that the percentage of cavalry of all types in a Late Roman army ranged from about 8% to a maximum of 20% of the total force. And as to the effectiveness of this cavalry, Ammianus gives a number of accounts where Roman cavalry performed less than admirably, even the heavily armoured Catafractarii/Clibanarii routed at Argentoratum and had to be personally rallied by Julian. At Adrianopolis the entire Roman cavalry force on both wings of Valens army fled the battlefield, leaving the infantry to fend for themselves (and the infantry fought on until nightfall allowed at least part of them to escape).

Its interesting to read peoples comments on how much more well equiped the Late Roman army was, especially the infantry with the Vegetian infantry man being armed with a Spiculum, a couple of javelins (veruta)and five darts (martiobarbuli). However, I can find no reference at all within Ammianus or the SHA to either martiobarbuli or plumbata, but many references to Spiculum and Veruta, and allow arrows. I'm not saying that the infantry did not have such hand hurled missile weapons, its just very odd that they are not mentioned by name.

I wont enter into a debate about the size of the Late Roman legion and Auxilia unit sizes, as the evidence is not at all conclusive (anyone know if the Perge inscriptions have been published yet?). But I would vouch that a 'typical' Late Roman field army size was around 25,000 stong, based on the sources.

Thank you for clearing some of these misconceptions up - I am no expert on the Late Roman military, by any means.

However, if I'm interpreting what you are stating here correctly, you believe that the cavalry-to-infantry ratio in the later Roman armies to be similar to that of the Imperial armies? If that is correct, then even more than previously would I argue that any such conflict between two such forces would essentially be a toss-up.