The Roman Army of Diocletian

[antiochus]

I will confess that the Late Roman army is not my main period of interest, but my research dictates I cannot avoid this period as it provides evidence of the Pythagorean system that governed Rome for nearly 1000 years has been terminated by Diocletian. This included removing the 35 tribes and the tribal assembly. However, before Diocletian did this, my research shows that Diocletian still used the tribal structure he inherited when he came to power in order to outline the size of the army and its organisation. In the Roman Pythagorean social and military structure, each Pythagorean age of time (amounting to centuries) is governed by a single integer that increases with time (in centuries). The organisation of the tribe and a legion for one of these Pythagorean ages is divisible by that single integer. Sometime back I did an experiment with the integer that governs the time frame Diocletian was emperor and applied it to the tribal system in a somewhat different manner than was usual.

By dividing each tribe by the single integer, and then adding the results of the 35 tribes, the Romans can have smaller legion to the number of 175 legions. The cavalry amounted to 700 squadrons, which would allocate each legion four squadrons. Although I have only used the military unit numbers in Ammianus and Zosimus, the result has a very very high compatibility rate. This has convinced me that Lydus’ cohort of 300 men and cavalry units of 300 and 500 men belong to the republic and principate.

I have gone through an on-line version of the ND and found 153 references to the term legion and 18 references of unclassified. This would bring the total to 171 if the unclassified were legions. I understand I am drawing a long bow here. Has there been a study on the ND in relation to the number of legions and possibly the size of the army required that I would find helpful? My main aim is to go after the organisation of the units rather than try and identify what troops types would make up a legion.

Please feel free to argue against the possibility of there being 175 legions as I have mentioned before, this is not my period and I am a duck out of water. Also do we know how many regions the Roman empire at this time was divided into?

Thanks in advance

Steven

[Renatus]

I imagine that A. H. M. Jones The Later Roman Empire, 284-602 and D. Hoffmann Das spätrömische Bewegungsheer und die Notitia Dignitatum might be useful starting points.

[Robert Vermaat]

Please feel free to argue against the possibility of there being 175 legions as I have mentioned before, this is not my period and I am a duck out of water. Also do we know how many regions the Roman empire at this time was divided into?

I recommend:
Nicasie, Martijn (1997): Twilight of Empire, the Roman Army from the Reign of Diocletian until the Battle of Adrianople, (Thesis Publishers Amsterdam).
Well you know this because you sent me a question about it already.

a) You must distinguish between old-style legions and new-style legions.
The old-style legions (styled legiones limitanei in the Notitia Dignitatum) are the classical ones, roughly 6.000 strong with ranks such as the centurion and the decurio etc. These units were in part broken up, some along cohortal lines of 500 to 1.000-strong units, but some were still 3.000 or even the original c. 6.000 strong. We don't know which legion had what strength at any time.
The new-style (styled legiones comitatenses in the Notitia Dignitatum) or 'Dioclenianic-Constantinian' units have new ranks such as the centenaruis and the primicerius and are much smaller.
Add to that the new units such as scholae, auxilia, etc., and I'm afraid you won't be able to develop a neat and tidy system in which to cast each and every unit.

b) When exactly? The military commands did not relate to the Roman civic regions (such a the provinces), but usually overlaaped the borders of these districts. Military commands were always being modified (usually becoming smaller), which makes it impossible to give one set of 'late Roman disctricts' to match one set of 'Late Roman units'.

[Timianus]

[quote="antiochus" post=348282]
Nicasie, Martijn (1997): Twilight of Empire, the Roman Army from the Reign of Diocletian until the Battle of Adrianople, (Thesis Publishers Amsterdam).
.

Ufta! $4500 on Amazon!

http://www.amazon.com/Twilight-empire-Di...+Battle+of

[ValentinianVictrix]

It is nigh on impossible to calculate the number of men in the Late Roman army from Diocletian onwards as there is currently no consensus on the size of any of the units, be they infantry or cavalry units. And using the Notitia is fraught with danger as some units appear in both the western and eastern sections, which is an excellent example of cross posting by the way. The other problem with the Notitia is the fact that we know some units are missing from that list. Jones calculated some were lost at Adrianople, and others would have been lost in various other clashes against the 'barbarian' tribes that encroached on the Empire during the 4th & 5th Centuries.
I'm still waiting for the full evaluation of the Perge fragments to be published as that may well throw a spanner in the works as its already clear from what has been published so far that it could well be that the Legiones during the last 5th Century were over 2000 men strong, which is not what one would expect at that period of the Empire's history.

Personally, my feeling , based on some research is that up to Adrianople the typical legion size would be between 2000 and 3000 men strong, with auxilia units being approximately 800-1000 men strong. Cavalry units were on average 200-300 men strong. But, as I say, this will be disputed by others!

[Robert Vermaat]

The other problem with the Notitia is the fact that we know some units are missing from that list. Jones calculated some were lost at Adrianople, and others would have been lost in various other clashes against the 'barbarian' tribes that encroached on the Empire during the 4th & 5th Centuries.

Lost from where exactly? Adrianople was c. 20 years before the ND, so the units which were destroyed there should not be expected in the ND anyway. More problematic is the absence of a great number of limitanei units (notably in Britain) and the duplication of other units which occur in one list and (after being transferred elsewhere) also in another list. It is not always clear if we are dealing with transferred units (and hence a duplicate), or a vexillation with the same designation as the original.

Of course we don't need the ND for total strength, as we are told by Johannes Lydus that the Diocletianic army numbered 390.000 (which is comparable to army sizes under Severus or Aurelianus).
The ND tells us that by the late 4th c., the army had 12 scholae palatinae,
146 field army legions or legiones comitatenses,
42 border legions or legiones limitanei,
97 auxilia palatinae,
85 field army vexillations,
196 cohortes, auxilia and milites,
253 border units of cavalry (ale, cunei equitum and equites)

If we assume that, on average, the scholae numbered 500 per unit, field army legions 1.000, border legions 3.000, auxilia palatina 800, border infantry units 300 and cavalry units 350, the total of units mentioned in the Notitia Dignitatum yields an army of about 450.000 men.
However, scholars such as Nicasie think this might be seen as a minimum rather than a maximum, to be taken as a more realistic number, as opposed to a 'paper strength'. The establishment strength could even be 650.000 if each cohort indeed was to be 500, and this number is what Agathius gives us for the 4th-c. army: 645.000 (Agath. V.13).

Note to those unfamiliar with the ND: this manuscript consist of two parts, probably originating c.394 AD. The part about the eastern empire was never augmented, but the part about the western empire was updated at least more than once, hence the duplications.

I'm still waiting for the full evaluation of the Perge fragments to be published as that may well throw a spanner in the works as its already clear from what has been published so far that it could well be that the Legiones during the last 5th Century were over 2000 men strong, which is not what one would expect at that period of the Empire's history.

Do you mean a strenght of 2.000 for a limitanei or a comitatenses legion? Or both? Based on?

Personally, my feeling , based on some research is that up to Adrianople the typical legion size would be between 2000 and 3000 men strong, with auxilia units being approximately 800-1000 men strong. Cavalry units were on average 200-300 men strong. But, as I say, this will be disputed by others!

Again, based on what? And why different after Adrianople?

[Flavivs Aetivs]

I'd agree that many units were paper strength, and many limitanei units may have only existed on paper by 425.

I however think 650,000 or 450,000 are absurdly high.

[Renatus]

The other problem with the Notitia is the fact that we know some units are missing from that list. Jones calculated some were lost at Adrianople, and others would have been lost in various other clashes against the 'barbarian' tribes that encroached on the Empire during the 4th & 5th Centuries.

Lost from where exactly? Adrianople was c. 20 years before the ND, so the units which were destroyed there should not be expected in the ND anyway.

Surely that is Adrian's point that, between the reign of Diocletian and the compilation of the Notitia, a number of units that might otherwise have appeared on the list were lost in battle, Adrianople being a major example.

[Robert Vermaat]

I however think 650,000 or 450,000 are absurdly high.

Why? 450.000 are not that much above what we think of army strengths of the Severan period or earlier.

[Robert Vermaat]

Surely that is Adrian's point that, between the reign of Diocletian and the compilation of the Notitia, a number of units that might otherwise have appeared on the list were lost in battle, Adrianople being a major example.

I understand that, but I don't understand why that would make the Notitia Dignitatum a problem. They did not make the list, period. It's the units that we know should be there but aren't which make it problematic.

[Renatus]

I understand that, but I don't understand why that would make the Notitia Dignitatum a problem. They did not make the list, period. It's the units that we know should be there but aren't which make it problematic.

The problem would be if Steven believed that he could use the Notitia to calculate the size of the Diocletianic army without appreciating that some units, as you put it, "did not make the list" because they had been lost in battle. He is probably fully aware of that but that is the point that Adrian was making.

[ValentinianVictrix]

As Michael pointed out, my point is that using the Notitia to try and calculate the size of the Late Roman army even from when the Eastern section has been dated from , approximately 395AD, is problematic as there are units noted in that section that then appear in the Western section, dated to approximately 420AD.

You would have to go through the Notitia with a fine tooth-comb an weed out from both sections units that appear in both. Then you would have to consult a variety of surviving works to look for unit names that no longer appear in the Notitia and then try and fathom out which ones were destroyed, disbanded, reformed under another name or were left off by the copyist for some obscure reason even though we have some sort of proof that the particular unit was still in existance at that time. Then after doing that you would then have the almost impossible task of trying to calculate how many men were in the various Laeti, Gentes, Navi, Numeri and Cunei units mentioned, plus the various Cohors and milites units, plus ripensis units etc etc etc. Good luck with anyone attempting that job!

The reason I believe the legiones in particular were larger than the 1200-1500 they are currently claimed to be is in part based on figures given by those such as Lydus who stated that during Julian's Sasanid campaign 1500 men of the Lanciarii and the Matiarii were tasked with taking charge of a tunnelling operation during one of the sieges Julian conducted. Now, its a bit difficult to interpret this passage, did Lydus mean 1500 men from each of those Legiones or the 1500 was divided between the two Legiones? Even so, 750 men drafted from a single legion deemed to be only 1200-1500 strong would seriously weaken the fighting ability of that legion. If however the legion in question was 2000-3000 strong then that figure does not seem that unreasonable.

Does anyone know if the Perge fragment information has been published yet as this may help out quite a bit?

[Flavivs Aetivs]

I however think 650,000 or 450,000 are absurdly high.

Why? 450.000 are not that much above what we think of army strengths of the Severan period or earlier.

The Battle of the River Frigidius, Adrianople, and the collapse of Gaul and Spain certainly destroyed a large number of units. The Salii replaced the Limitanei guarding the Rhine.

I go with the conservative estimates of Goldsworthy, Jones, and Heather who say around 200,000 men in the time of the Notitia.

[Nathan Ross]

Was the original post specifically about the army of Diocletian, or the later Roman army generally? The two could be very different things.

If it's the 284-305 period in particular, this thread might be interesting:

How many Legions were there in the Tetrarchy?

Ritterling's table of legions (in that thread) suggests between 50 and 64 in existence in Diocletian's day. Since we know that both II and VI Herculia had ten cohorts, and Vegetius tells us that a legion had 6000 men, we could assume that each of these legions was a full scale (Severan) formation of c.5000-6000 men.

I think it most likely that the tetrarchic army was based on these traditional legions, with field armies made up of detachments drawn from the legions. Only in Constantine's day did these smaller mobile detachments become 'legions' in their own right.

If we can further assume that the later Romans kept up the approximate 50/50 split between legions and 'support troops' (cohorts, alae, equites, cunei, etc), we would have a total army number of somewhere around 500,000 under Diocletian. This is, of course, 'paper strength'.

The figures given by John Lydus may represent the official size of the army when Diocletian came to power - i.e. the Severan organisation. By his day this would have been in tatters, but a sober administrator intending to reform the army would first have to determine how big it was supposed to be...

We don't know, of course, how or even whether Diocletian actually instituted reforms - I suspect most of the changes happened under Constantine. But we do know (as noted in the thread linked above) that a 'tribunus batavorum' existed in AD303, and he went straight on to a provincial ducate - so he was not a traditional auxiliary commander. Perhaps something like the 'auxilia palatina' of later decades already existed at this point? That might throw out the numerical calculations based on legion strength, but at present there's no way of checking any of our estimates.

[antiochus]

Robert wrote:
I recommend: Nicasie, Martijn (1997): Twilight of Empire, the Roman Army from the Reign of Diocletian until the Battle of Adrianople, (Thesis Publishers Amsterdam). Well you know this because you sent me a question about it already.

Until now I didn’t know about this. And thank you for giving the dates of those references.

Nathan wrote:
Was the original post specifically about the army of Diocletian, or the later Roman army generally? The two could be very different things.

Yes it is specifically about the army of Diocletian. The size of the legion when Diocletian comes to power is 6000 men. I have taken the premise, the 6000 man legion has been divided by five to get five legions of 1200 men. With a tribe capable of levying 6000 men, the 35 tribe equates to 210,000 men organised into 175 legions. The 6000 man legion has three sizes, 5000 men, 5500 men and 6000 men. The 6000 man legion has both a horizontal organisation based on 500 men and a vertical organisation based on 600 men.

This is what Isidore is telling us when he states a 6000 man legion was organised into 12 cohorts of 500 men. It also has 10 cohorts of 600 men. I would appreciate if members do not engage me in a debate about the reliability of Isidore because no one has proven to me his numbers are incorrect. I’ve been compiling the cavalry numbers in Ammianus and Zosimus and this is convincing me that the organisation of the units throughout Ammianus and Zosimus is derived from the organisation of the cavalry as given by Vegetius in regard to the 6000 man legion. Ammianus (24 5 10) has the emperor reduce the surviving members of the cohort, to the infantry service with loss of rank. Here, like the Vegetius legion, each infantry cohort is assigned a body of cavalry. Zosimus mentions a figure of “about 360 men,” which could be rounded from 330 men and is half the number of cavalry taken from Vegetius if you take away the cavalry assigned to the double cohort.

By following, Ammianus, with the army consisting of cohorts, maniples and centuries, I believe this is derived from the 10 cohort organisation and not the 12 cohort organisation.

Renatus wrote:
The problem would be if Steven believed that he could use the Notitia to calculate the size of the Diocletianic army

I was only interested in how many times the word legion was used in the ND. I’m more interest in trying to establish if there is a mathematical link between the organisation of the Vegetius legion and the numbers in Ammianus and Zosimus.