Full Version: Manpower for Diocletian\'s new legions
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I've read (and re-read) Duncan Campbell's article in the latest Ancient Warfare about Diocletian's army reforms. Much of the scholarly debate has been about how many legions were raised and if they were "old-style" with 10 full cohorts. The question that I have not seen addressed is where that manpower came from? Did Diocletian come up with 50-100,000 more men?

One theory I remember reading about was that they were created from sweeping old Principate auxiliary cohorts into newly branded legions. It seems plausible with the loss of citizenship distinction between auxiliaries and legionaries after Caracalla. Has anyone done research into this? Do many of the old Principate auxiliary cohorts disappear from the record at around the time that the Jovia and Herculia legions appear?

Quote:Did Diocletian come up with 50-100,000 more men?[..]
Do many of the old Principate auxiliary cohorts disappear from the record at around the time that the Jovia and Herculia legions appear?
Many units disappear from the record during the troubles of the 3rd century, but even if they were disbanded at some point to form new-style regiments, we would not know about it. As we know from later cases, units could be split and re-stocked (or not). The main thing to realise here is that there was not a single 'Roman military Practise' which was universally applied. What we do (seem to) know however is that ranks and other trappings of new-style units were different from the familiar ones of the old-style units. My personal guess would therefore be that new regiments were newly created. Either with cadres from other units, or from scratch. The 'extra' manpower would have been available, either by offering financial rewards to citizens of non-citizens. And referring to the latter - no, I am not of the opinion that the Romans suddenly employed only barbarians, as some (ancient) authors suggested.
This is an interesting question. I have not read Duncan's article, so quite possibly it addresses this issue directly, but on the formation of the Joviani and Herculiani legions in particular the ever-opaque Vegetius has this to say:

We formerly had two legions in lllyricum, consisting of six thousand men each [who had] supported for a long time the weight of all the wars and distinguished themselves so remarkably that the Emperors Diocletian and Maximian on their accession honored them with the titles of Jovian and Herculean and preferred them before all the other legions.
Vegetius, De Re Militari I.17

This would suggest that two old principiate legions from the Danube were renamed Jovia and Herculia in c285. Unfortunately, all the legions of the old Danubian garrison remain, in name at least, either in the ND or in inscriptions dated post-Diocletian. Perhaps Vegetius is referring to combined auxiliary units, the word 'legion' being perhaps a little mutable by his day?

I also wondered whether these supposed 12000 men (from the two old legions) might have been split into six new style legions of 2000 men or so, which in turn were named I, IV and V Jovia, and II, III and VI Herculia, the two corps being collectively referred to as Joviani and Herculiani. I don't think there's any real evidence for this, unfortunately, beyond the units listed in the ND and the supposition that they were probably raised around the same time...

Then again, as Robert says, these legions could just as well have been new formations, perhaps built on a cadre of Danubian veteran troops.