Late Roman Unit Sizes

[Nathan Ross]

Eunapius: Then a squadron (ίλη) of heavy cavalry (kataphrakton)over four hundred strong crashed into the rearguard.(56) (fragment 27.8 (Suda I 311)

Yes, I came across that one a while back, also in Blockley. An ίλη would be a Roman ala, of course, which would suggest c.500 men, but the phrasing here suggests that this one was unusually large! Mind you, we've seen how hazy these late sources could be with terminology. Actually, I'd assumed the squadron was Roman, but you're quite right that it's more likely Persian.

3,000 armoured soldiers ( ὁπλίται ) against Arzanene, in what is called a moira

That would seem close to the Lexicon Militare's estimate of 2400 above. But aren't these terms (and the unit sizes they describe) connected to the reorganisation of the 'Byzantine' army towards the end of the 6th century? I don't know much about that, but I believe there were some major changes from the older Roman system.