How many legions were there in the Tetrarchy?

[Marja]

This is a working list and I'm going to start from Britain and work around to Africa over several edits.

Permanent Field-Army Legions (at least 2 legions)
- Lanciarii Seniores [LP, Or. v]
- Lanciarii Iuniores [LP, Or. vi]
- Mattiarii Seniores [LP, Or. vi]
- Mattiarii Iuniores [LP, Or. v]
- possibly Armigeri Propugnatores Seniores (?) [LP and LC, Occ. v.]
- possibly Armigeri Propugnatores Iuniores (?) [LP, Occ. v.]
- possibly Armigeri Defensores Seniores (??) [LC, Occ. v.]
- possibly Armigeri Defensores Seniores (??) [not listed]

- I'm not counting the Iovii, Herculii, Divitenses, Tungrecani, etc. here, because they are derived from border legions.
- I'm only including the Armigeri Defensores because the titles of the Armigeri Propugnatores seem to imply an intended contrast with Defensores.

Brittaniae (probably 3 legions)
- II Augusta
- VI Victrix
- XX Valeria Victrix, possibly "Solenses," based on Ueda-Sarson's arguments
- possibly a 4th British legion, based on Nischer's arguments

Hispania (1 legion)
- VII Gemina

Galliae (possibly 10 legions)
- I Minervia [in Germania Secunda]
- XXX Ulpia
- "Divitenses" (P.S. definitely II Italica Divitensium, see Nathan Ross http://www.romanarmytalk.com/rat/17-roma...tml#320916 )
- "Tungrecani"
- VIII Augusta [in Germania Prima]
- XXII Primigenia
- I Flavia Pacis, based on a militum in the Notitia
- II Flavia Virtutis, based on the Notitia
- definitely a legion, possibly I Martia [in Sequanica]
- III Flavia Salutis [somewhere on the Rhine, based on its association with the other two]

- XII Victrix is attested
- It's possible that some of these legions are synonymous

Italia (possibly 4 legions)

- III Italica [in Raetia]
- possibly II Parthica, but I'm going to list that in the east
- possibly I Iulia Alpina, if the Claustra Alpium Iuliarum already existed
- possibly II Iulia Alpina
- possibly III Iulia Alpina

[Nathan Ross]

Papyrus Oxyrhynchus 43 lists Danubian legions in the field army in Egypt.

I've never actually seen the whole text for this one, as I don't have 'Roman Records on Papyri' or wherever everyone else gets their information from! I'm only relying on mentions in Leadbetter and elsewhere. Do you know of an online transcript, or could you provide the text here if it isn't too ridiculously extensive?

I figure that these legions must have been at least 2,000 strong when formed, since they contribute at least 1,000 to the field army and retain at least 1,000 in the border army.

But these are units taken from the Notitia Dignitatum - so they date from around a century and a half after the Tetrarchy. Granted many of them may have been formed by, or before, Diocletian and Constantine, but surely not all and not in this arrangement. The division between Seniores and Iuniores surely dates to the end of Constantine's reign (Nicasie's suggestion) at least.

Neither was there a strict division between 'border' and 'field' legions at this point, I think. There were the traditional legions, most of them in their traditional stations on the frontiers, which provided vexillations to make up the field armies. These vexillations may have operated for decades independent of their parent units, but were not regarded as new 'legions' yet, nor named as such. Interestingly, II Italica Divitensis may have been the first example of a vexillation being reclassed as an independent legion - and in this case it takes its name from a frontier garrison post. Constantine (or somebody) clearly used it in the field though, as those Via Flaminia tombstones attest.

The two 'legions' listed on the Ritterling table above for Aegyptus Herculea are, I would think, vexillations of their parent units on the Danube. Otherwise I believe the list is probably accurate - around 50 legions for c.AD300 (existence of the higher-numbered Herculia and the Alpina legions is dubious, I think!), with each legion +/- 4000 men. Total legionary strength for the empire thus 200,000 or so.

[Marja]

Do you know of an online transcript, or could you provide the text here if it isn't too ridiculously extensive?

Grenfell and Hunt, the Oxyrhynchus Papyri, Part I, via the Internet Archive.

Neither was there a strict division between 'border' and 'field' legions at this point, I think.

True. In some ways it's drawing forward from the early third century, when there were legions and vexillationes, and the later fourth century, when there were limitanei/ripenses and comitatenses and palatini. I should probably contrast legions with permanent bases, detachments from them, and legions with no permanent bases.

I'm trying to estimate the relative strengths of the Tetrarchan field armies by working out the strengths of their border armies. And it seemed worth hashing out a rough list and estimate.

[Nathan Ross]

Marja - some quick notes based on your working list above:

Permanent Field-Army Legions

As I said, I don't think there were 'permanent' field legions at this point. The legionary strength of field armies was made of detachments drawn from traditional legion bases on the frontiers.

Seniores/Iuniores

The earliest attestation for this division is AD356 (Nicasie) - it probably dates to Constantine's reorganisation of the army amongst his sons.

Lanciarii

The position of the lanciarii is a bit obscure - I'd be wary of assuming them to be an independent military unit. Valerius Thiumpus was a lanciarius of the 'sacred comitatus', and he and a couple of others moved there from Danubian legions. It may have been more a status (like 'protector') than a unit though.

Mattiarii - Armigeri

Surely not 'legions', but auxilia of some sort at this date.

Brittaniae (probably 3 legions)

XX Valeria Victrix may have disappeared after Carausius. I'm unconvinced about their being renamed! No evidence for another legion being added to the province that I know of.

"Divitenses" - "Tungrecani"

The Divitensis were surely Legio II Italica Divitensis, a proper legion based on the Rhine but used in the field (by Constantine?). How big it was is anybody's guess! Tungrecani may be laeti from old Tungria, perhaps?

Flavia Pacis/Virtutis/Salutis

Can we assume the existence of these? If so, then without their Christian cognomens - so just three legions of some sort... I don't see the evidence really. Constantine could have raised any number of legions called Flavia something though, I suppose...

[Marja]

I thought that Divitia had vexillationes from at least two legions, II Italica and one other, possibly VIII Augusta. I suspect that they were reorganized into their own independent legion. It wouldn't be unheard-of for them to share the name and number of one of the original legions there were formed from - like the V Macedonica - but it is also possible for them to have a new designation. Is there late Tetrarchan or post-Tetrarchan evidence that they were still going by II Italica?

I figure that since the Divitenses and Tungrecani are so often paired [and the Fortenses and Nervii after the eastern Divitenses and Tungrecani have been officially disbanded], that they must have similar status, if not similar origins.

[D B Campbell]

I don't accept ... Nischer's chronology with the field armies only dating to Constantinus I.

I think that was the only bit I agreed with! I confess that I didn't read your earlier posts very carefully, and only just realized that you're assuming the existence of Tetrarchic comitatenses. The gist of my Ancient Warfare article was that Diocletian did not have a "field army" in the sense of the later comitatenses. I believe that the evidence (such as it is) has been misinterpreted.

My best guess, is that there were about 39 legions in 284 and about 64 in 305.

We don't really need to guess, though. I don't see any reason to disagree with Parker's estimate of 54 full-strength Diocletianic legions. Given that Severus left 33 legions, where do you get your 39 and 64 from?

[Nathan Ross]

Is there late Tetrarchan or post-Tetrarchan evidence that they were still going by II Italica?

The main II Italica legion is still in Noricum, of course, in the Notitia Dignitatum: Praefectus legionis secundae Italicae .

The Italian tombstones I mentioned before, however, clearly show that II Italica Divitensis was its own formation. Each of them, interestingly, gives the legion a slightly different name, and one leaves out the Divitensis bit. This would imply that at this point the name had been recently introduced, or perhaps was even unofficial:

CIL 11, 04787 Spoleto
D(is) M(anibus) / Florio Baudioni viro ducenario / protectori ex ordinario leg(ionis) II Ital(icae) / Divit(iensium) vix(it) an(nos) XL mil(itavit) an(nos) XXV Val(erius) / Vario optio leg(ionis) II Italic(a)e Divit(iensium) / parenti karissimo / m(onumentum) f(aciendum) c(uravit)

CIL 11, 04085 Ocriculum
D(is) M(anibus) / Val(eri) Saturnani mil(itis) / leg(ionis) II Ital(icae) qui vix(it) / an(nos) XXX mil(itavit) an(nos) XIII / co(ho)r(te) VI / Val(erius) Laupicius fratri / karissimo / m(onumentum) f(aciendum) c(uravit)

AE 1982, 00258 Ocriculum
D(is) M(anibus) Val(erius) Iustin/us miles legionis s/ecund(a)e Italic(a)e Divite/nsium civis R(a)etus / militavit annis V / vixit an(n)is XXV co(ho)r(ti)/s VII Secundus fra/tiri patri carissim/o bene merenti / memoriam feci/t

CIL 06, 03637 Roma
D(is) M(anibus) s(acrum) / Val(erius) Genialis miles / legionis secund(a)e / Divitensium Italic(a)e / signifer vixit annos L / militavit annos XXVI / pos(u)it Verina bene merenti

I think you'll agree that these four men probably came from the same unit (Baudio moving from ordinarius to protector), and perhaps fell in the same campaign - probably Constantine's advance on Rome down the Flaminian Way.

But how and when the unit moved from being a vexillation of II Italica from Noricum (but recruiting in Raetia, it seems) to being an independent legion and then to being a unit called the Divitensis we don't know...

[Marja]

I think Parker estimates about 33 in 211, +6 by 285, +17 by 305. He thus estimates 56 legions, or 51 if we exclude those units in Africa and the Rhine where the Notitia is inadequate. Allowing for losses, yes, that comes to about 54.

I know that 1 or 2 legions were destroyed between 211 and 284, so I'm not quite sure how I got 39 legions in 284 instead of 38. My notes are messed up, but they number 39 legions if we exclude the legiones Iuliae Alpinae. But as for a total in the mid-60s for 305 or at the latest 312, here's where I'd disagree with some lower estimates:

1. Because units of the I Flavia Pacis and II Flavia Virtutis appear in the limitanei of the Dux Mogantiacensis, I consider them Tetrarchan border/garrison legions, and assume the same of the III Flavia Salutis. (+3)

2. I am not aware of any evidence that the XX Valeria Victrix had been destroyed. (0 to +1 depending whether Parker counts them - I can't tell)

3. I don't see any reason for Constantinus or Constantius to form the Claustra Alpium Iuliarum, and I think Diocletianus faced worse crises along the middle and upper Danube, so I date it and the associated legions back to the Tetrarchy. (+3)

4. I suspect that Galerius formed a few legions, which Constantinus may have renamed as the I Flavia Gemina and II Flavia Gemina. (0 to +2)

5. I allow for a few additional legions in Cyrenaica [since the chapter is lost] and Africa [since the chapter doesn't name legions], because there had been such a dramatic increase in Aegyptus. (+2 to +3)

6. I count some permanent garrison detachments, such as the Divitenses, Tungricani, and the Egyptian units of the V Macedonica and XIII Gemina. (+4)

[Marja]

I haven't really explained this clearly enough, but I think the Tetrarchy was able to form so many legions because they would form field armies from the border armies and then, if necessary, form new border armies, including new legions, from the field armies. I think there were a few permanent units, but mostly temporary ones.

I don't think Constantine and his successors were able to form as many legions because they had separated the field army units from the border army units, making it harder to use field army units to reinforce the border armies.

So if the same unit is attested in the field armies and the border armies, it is likely to predate the division between ripenses/limitanei, comitatenses, and palatini.

I get the impression that Constantinus and his successors were more interested in the field armies than the border armies. If Diocletian's expansion of the army overstretched imperial resources, Constantine and his successors would more readily have accepted deterioration of the border armies than the field armies. That said, there were, for example, campaigns of restoring and adding to the frontier fortifications. Valens and Valentinian did form two new garrison legions in Egypt, but generally, new units would have been less common than before.

[Nathan Ross]

I believe that the evidence (such as it is) has been misinterpreted

What evidence might there be, actually, for a Diocletianic comitatensis? I know of the 'sacred comitatus', or imperial retinue, to which various military units and detachments were added as temporary or semi-permananent field forces. But beyond that...

I suspect that Galerius formed a few legions, which Constantinus may have renamed as the I Flavia Gemina and II Flavia Gemina.

Why Galerius, particularly? He had the time and inclination to raise troops, but Licinius had more of both! Besides which, nobody (except Maxentius) was actually at war with Galerius, and his memory was not condemned after death, so it's less likely that any of his formations would have been subsequently renamed.

I think the Tetrarchy was able to form so many legions because they would form field armies from the border armies and then, if necessary, form new border armies, including new legions, from the field armies.

This would depend on there being 'field' and 'border' armies. Most of the wars of the tetrarchy (aside from the civil wars) actually happened on the frontiers anyway: on the Danube, the Persian front, in Egypt, Mauretania, Britain and on the Rhine. Detachments were moved from one border area to provide field forces in another, but this was no innovation and had been happening since the 1st century. I still don't see evidence for any of these detachments becoming new legions yet.

[Marja]

What would you call Diocletian's campaigning armies, if not field armies?

Again, with Payrus Oxyrhynchus 43, there are units from at least two Danubian provinces, deployed as a campaigning army in Egypt. I thought the question was whether Diocletian formed field armies:

1. Like the Antonines and Severans did, with temporary vexillationes from multiple border armies.

2. Like Constantine did, with permanent units separate from the border armies.

3. Or some other way.

4. Or something closer to 1 at the beginning and something closer to 2 at the end.

[Nathan Ross]

What would you call Diocletian's campaigning armies, if not field armies?

Sure, there was the field army (comitatus), or rather armies - but the question is whether there were independent legions or other units permanently 'of the comitatus' (comitatensis), i.e. distinct from the regular legions based on the borders.

I still don't think there were - not under Diocletian anyway. I believe his field forces and those of his collegiate emperors were formed, as you say, by 'temporary vexillationes from multiple border armies'. All the individual legionary units mentioned in the various tetrarchic field army listings we have appear to be of this sort.

So I would say the change happened late in Constantine's reign, when an unusually long period of peace (for that era!) and the prospect of a division of the empire among his sons allowed for a full reorganisation of the army structure. The seniores/iuniores split possibly happened at the same time.

The only exception I can think of would be the various bodies of barbarian troops taken into the imperial field armies under the tetrarchy - Crocus and his Alamanni under Constantius, for example. These appear to have been irregular formations initially, probably called numeri, and attached to the comitatus for perhaps a single campaign. In time they may have evolved into more regular standing formations - perhaps the auxilia palatinae of the later 4th century.

Another point: I suspect that Legio II Britannica might have been formed under Constantine, perhaps by combining vexillations of the British legions - for the Italian campaign of 312, perhaps? The name sounds like an old-style legion, but it later turns up as comitatensis...

[Nathan Ross]

This essay might be of interest - a 1975 thesis by John F Hall of Brigham Young University:

The Military Reforms of the Emperor Diocletian

Essentially Hall agrees with Parker's position and opposes Nischer. There's not too much here that isn't found elsewhere, but it's a useful restatement of views.

Oddly, Hall keeps referring to Oxyrynchus Papyri 90, which as far as I can tell concerns a payment of corn. Presumably he means 43, which we mentioned above. I'm not convinced by Hall's idea that the Acta of Sergius and Bacchus prove the existence of Diocletianic Scholae either - the text was probably composed much later, using anachronisms...

[D B Campbell]

This essay might be of interest - a 1975 thesis by John F Hall of Brigham Young University ... There's not too much here that isn't found elsewhere, but it's a useful restatement of views.

I just skimmed through, but it seems to be heavily indebted to Seston, who wrote 65 years ago. It's dangerous, particularly where archaeology is involved, to rely on material that's so old. Hall's view of Diocletian's work on the frontiers is a bit of a self-fulfilling prophecy -- if it's late Roman it must be Diocletianic, because Lactantius says that he built a lot. Also, in my opinion, it's not a great idea to use the N.D. as a Diocletianic source.

Oddly, Hall keeps referring to Oxyrynchus Papyri 90, which as far as I can tell concerns a payment of corn. Presumably he means 43, which we mentioned above.

P. Oxy. 43 spans pp. 89-100 in Grenfell & Hunt. Presumably Hall is citing the page number?

[Nathan Ross]

it seems to be heavily indebted to Seston

Is there an English translation of Seston? Would it even be worthwhile reading now?

Also, in my opinion, it's not a great idea to use the N.D. as a Diocletianic source.

Hmm. Am I right in thinking that the only 'new' legions mentioned in the ND for which we have an independent corroboration dated pre-Constantine would be I Iovia and II Herculia?

Presumably Hall is citing the page number?

Ah yes, that would make sense! :grin: