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Late Roman Unit Sizes
Here’s a basic summary of my investigation into the so-called Late Roman legion.

A full strength the legion includes both the iuniores and seniores. What is horrendous about this legion is the legion’s horizontal organisation has the same number of men as its vertical organisation.

The legion of iuniores and seniores is reduced in size with the removal of the reserves. I use the term “reserves” as this is mentioned in the battle of Adrianople. I have no idea what the correct troop types would be for this period. So with the removal of the reserves, both iuniores and seniores, the legion is reduced in size by one third.

Next arrangement is a full strength legion includes both the iuniores and seniores. However, then the seniores are removed.

Next, the legion consists of all the iuniores, but this time, one vexillation is removed.

Next, the legion consists of all the iuniores, but this time, the reserves of iuniores are removed.

Next, the legion consists of all the iuniores, but this time, the reserves and one vexillation are removed.

Now think of all the number possibilities you can get.

At present, with the seniores (infantry), I have a cuneus amounting to six centuries, and without the seniores, five centuries. This is because the seniores represent one-sixth of the iuniores. For the cavalry, with the inclusion of the seniores, six squadrons, and without the seniores, five squadrons of iuniores.

Malalas writes that Julian “set as scouts brave men from the arithmos of the lanciarii and the mattiarii 1,500 men. Ammianus also confirms the number of soldiers to be 1,500 men. From Sozomen, I know the size of an arithmoi, but I have no idea of how many men were selected from each arithmoi as there is no information as to the number of arithmoi of the lanciarii and mattiarii. From my organizational chart, the 1,500 men would be reorganized into to five units each of 300 men.

Ammianus writes that “the emperor Constantius demanded 300 picked men from each numerus in Julian’s army.” Again in 378 AD, Ammianus writes that Sebastianus had been directed to choose 300 soldiers from each numerus to meet the Goths at Adrianople.

Are these translations of Ammianus correct? Does it actually say “numerus”? Also when the Romans selected men from various units, they have two methods I have become aware of, men and generally replacements selected from each century, and the second method is to select whole centuries. In this manner, the officers accompany the century, so no need to find new officers.

Most of the conclusions I have come to boils down to the Late Roman army being based on the vexillation organisation with or without the seniores and the reserves. Sometimes, well most of the time, if feels like two extra wheels have been added to the enigma machine.
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(01-20-2021, 08:32 AM)Steven James Wrote: Now think of all the number possibilities you can get.

Why would any army have such a complicated organisational structure? And what makes you think seniores and iuniores were originally combined in the same units?


(01-20-2021, 08:32 AM)Steven James Wrote: ...from the arithmos of the lanciarii and the mattiari... I know the size of an arithmoi... selected from each arithmoi... no information as to the number of arithmoi of the lanciarii and mattiarii.

ARITHMOS is singular. ARITHMOI is plural. They are the same as NUMERUS and NUMERI in Latin. The numerus of the Lanciarii and the numerus of the Mattiarii are both arithmoi, or numeri.


(01-20-2021, 08:32 AM)Steven James Wrote: Are these translations of Ammianus correct? Does it actually say “numerus”?

Yes.

20.4.2: Aerulos et Batavos cumque Petulantibus Celtas et lectos ex numeris aliis trecentenos

31.11.2: trecentenis militibus per singulos numeros lectis Sebastianus properare dispositus est.

The division seems quite simple to me. A numerus probably comprised c.600-800 men. Maybe up to 1200 for some legions. A detachment of 300 men is marched off to a war in the east. This detachment later forms a new unit with the additional title Iuniores, now based in the east, and is recruited back up to establishment size. The original remaining unit of 300-500 in the west is also recruited back up to size, and given the title Seniores to distinguish it from the new one. Operational strength, of course, may have remained low for some time in both cases.

At any point subunits of several hundred men can be taken from the numeri and either used as temporary detachments (as with the Adrianople example here), or combined with other detachments to form temporary mixed units for special duties (as with the Lanciarii and Mattiarii in Persia).

Very simple, very practical - a flexible military system to meet the needs of a complex era!
Nathan Ross
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Nathan wrote:
Why would any army have such a complicated organisational structure?
 
Well I would not say it was complicated from a Roman point of view, with them having a full understanding of the organization. But with the limited amount of information we have and some of the numbers, like 800 men being equally the number of men in the horizontal organization of a legion and also 800 men in the vertical organization of the legion, does leave me wondering which organization they could be referring to (horizontal or vertical).
 
Nathan wrote:
And what makes you think seniores and iuniores were originally combined in the same units?
 
That is my conclusion based on my tribal research.
 
Nathan wrote:
The division seems quite simple to me. A numerus probably comprised c.600-800 men. Maybe up to 1200 for some legions.
 
Thank you for clearing up the Ammianus translation. Taking your lowest figure of 600 men for a numerus, Constantine’s demand for 300 men from each numerus would mean that Constantine was seriously intent on weakening Julian’s army.
 
Nathan wrote:
A detachment of 300 men is marched off to a war in the east. This detachment later forms a new unit with the additional title Iuniores, now based in the east, and is recruited back up to establishment size. The original remaining unit of 300-500 in the west is also recruited back up to size, and given the title Seniores to distinguish it from the new one. Operational strength, of course, may have remained low for some time in both cases.
 
Our theories have one similarity. I believe the seniores being one-sixth of the iuniores when detached, could also be increased to their permitted maximum strength, which would be equal to the iuniores.
 
Nathan wrote:
At any point subunits of several hundred men can be taken from the numeri and either used as temporary detachments (as with the Adrianople example here), or combined with other detachments to form temporary mixed units for special duties (as with the Lanciarii and Mattiarii in Persia). Very simple, very practical - a flexible military system to meet the needs of a complex era!
 
I can’t argue with that.
 
Following Sozomen’s six arithmoi, amounting to about 4,000 men, I find the arithmoi unit size only comes into play when I remove the reserve centuries from the legion. For this to work, the seniores must be included in the legion. If I remove the seniores, the arithmoi organization goes out the window, but the vexillation system dominates. I haven’t done this out of sheer randomness, every removal of something has to match data in the primary sources.
 
You write that a numerus “probably comprised c.600-800 men, maybe 1,200 men. For me personally, I want more information, like how many centuries and how many men in a century. If it was 80 men, then I would have to rule out a numerus being 600 men as 80 men per century do not divide by 600 men. As the 80 men per century and the 800 men per numerus are compatible, and create 10 centuries, then how are they deployed? Ten centuries wide by one century deep, two centuries wide by five centuries deep, or five centuries wide by two centuries deep? How is each century deployed? Twenty wide by four deep? Ten wide by eight deep? Etc. etc. A critical examination of the data cannot be overlooked, and can produces some surprises .
 
I’ve deducted what the size of an infantry century is. It has been tested against the data and has stood the rigors. There are two examples in Ammianus that indicate rounding, and not by much. The size of a century conforms to the frontage required for forming cavalry lanes. The frontage of the cavalry lanes made by the infantry does determine the frontage of the cavalry squadron. Then it is a matter of choosing the depth of the cavalry squadron by elimination with the cavalry numbers found in the sources.
 
Ammianus mentions seven legions and a number of numerii amounting to 20,000 men were stationed at Amida. Basing my calculations on the legions consisting of only iuniores and my calculation of the size of a numerus as per the size of Sozomen’s arithmos, I get exactly 20,000 men as per Ammianus, so something is working for me.
 
My anguish lies in that I do not fully understood what some of the Roman military doctrines are for the Late Roman legion and army. Are the Romans still stripping cavalrymen from each squadron in the army to form the commander’s guard cavalry? If this doctrine was still in play, then Julian would have to have a total of 1,200 cavalry at Strasbourg so as to have 200 guard cavalry.
 
Adrianople tells me they are still using the reserves to guard the baggage, as per the old triarii doctrine, which indicates the three line deployment is still in play. However, the number of centuries I have for an arithmos/numerus are only for a two line deployment. If I add the reserves, then what should such a unit be called if a numerus only applies to a two line deployment?
 
For every question I answer, I seem to be creating another question. I do prefer any period from the beginning of the republic up to the start of Diocletian’s reign. The army for those periods makes more sense and is far more logical. Plus there is more information to cross reference.
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(01-20-2021, 03:06 PM)Steven James Wrote: Taking your lowest figure of 600 men for a numerus, Constantine’s demand for 300 men from each numerus would mean that Constantine was seriously intent on weakening Julian’s army.

Possibly. Or the numeri he requested in full were only c.600 men, and the rest were 800-1200?

Most likely a standard troop draft anyway. Julian probably did much the same when he assembled his own expeditionary force and marched east.


(01-20-2021, 03:06 PM)Steven James Wrote: You write that a numerus “probably comprised c.600-800 men, maybe 1,200 men. For me personally, I want more information, like how many centuries and how many men in a century.

I'm tending to find that Vegetius (II.14) probably had it right - 110 men under one centurion and one standard bearer. This subunit variously referred to as a century, ordo or 'cohort'.

So a numerus auxilium might consist of six subunits (of 110+2 men each) making 672 men. These would be numeri, or arithmoi, like the six that Sozomen mentions being sent to Ravenna. A larger auxilium or a palatine legion might consist of eight subunits (896 men) and a comitatensis or limitanei legion ten subunits (1120 men). In all cases the number could be rounded up for paper strenth, or reduced for operational strength or after the detachment of temporary service units.

Still very hypothetical, but the kind of figures this produces seem to be more or less in tune with the few source estimates we have.


(01-20-2021, 03:06 PM)Steven James Wrote: Ammianus mentions seven legions and a number of numerii amounting to 20,000 men were stationed at Amida... I get exactly 20,000 men as per Ammianus, so something is working for me.

No - this is often misquoted. Ammianus (19.2.14) says intra civitatis ambitum non nimium amplae legionibus septem et promiscua advenarum civiumque sexus utriusque plebe et militibus aliis paucis ad usque numerum milium viginti cunctis inclusis - "for within the limits of a city that was none too large there were shut seven legions, a promiscuous throng of strangers and citizens of both sexes, and a few other soldiers, to the number of 20,000 in all."

The version by Clark (c.1911, I think) adds an extra word to make milium centum viginti - 120,000 - and this is sometimes quoted as the original. But Clark was obviously thinking that a legion was c.6000 men. In fact the amendation is unnecessary.

There was only one legion stationed in the city - V Parthica - and the other six had retreated before the Persian advance, having abandoned their positions and/or been defeated. So they almost certainly would not have been at full strength. So if we give V Parthica a full strength of 1200 men, and the others a generous 800 each, we get a figure of 6000 men for the legionary garrison. This is probably still too high. But if so, the remaining 14,000 people would be the inhabitants of the town, refugees ('strangers') and irregular troops.
Nathan Ross
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(01-20-2021, 03:06 PM)Steven James Wrote:
Constantine’s demand for 300 men from each numerus would mean that Constantine was seriously intent on weakening Julian’s army.


I assume we are talking about Constantius II, not Constantine II? (Constantine, Constantius, Constans... Why Constantine would not name his sons with clearly differing names  Angel is beyond me).
Robert Vermaat
MODERATOR
FECTIO Late Romans
THE CAUSE OF WAR MUST BE JUST
(Maurikios-Strategikon, book VIII.2: Maxim 12)
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How does the Perge Legion size as per the Anastasius Edict affect these calculations?
Adrian Coombs-Hoar
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(01-20-2021, 08:52 PM)ValentinianVictrix Wrote: How does the Perge Legion size as per the Anastasius Edict affect these calculations?

I calculated the Perge legion to be 1172 infantry (I now suspect 1162 to be more likely) with an attached unit of 300 cavalry (or 310, as I now believe).

The legion breaks down into ten subunits, each consisting of 110 infantry (10x11 phalanx formation) with six additional men (NCOs etc and ordinarii). As such it's more or less in line with the estimate I gave above, for the upper end of the range, although there are rather more NCO types than usual... The cavalry unit is also ten subunits, each of 28 men (4x7 formation) plus ordinarius, nco and vexillarius.
Nathan Ross
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Didn't Onur calculate the Perge Legion to be around 2000 strong, including the cavalry and supernumeraries, hence his belief it was a double strength legion?
Adrian Coombs-Hoar
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(01-20-2021, 09:39 PM)ValentinianVictrix Wrote: Didn't Onur calculate the Perge Legion to be around 2000 strong, including the cavalry and supernumeraries, hence his belief it was a double strength legion?

In his 2017 paper in Gephyra Onur estimates that "the total number of men listed in the schedule is no less than 1550-1600" (p.197, abstract), although he does not give a calculation as to how he arrived at this figure.
 
He earlier says (p.187): "In any case, the legions of field armies contained between 1000-1200 men in the fourth century. The size of the unit in the inscription of Perge cannot be deduced because the last lines containing the numbers of munifices, perhaps clerici and deputati are deficient, missing or perhaps have been restored incorrectly by the editor. Even though the number of these is uncertain, the minimum total number is 1172. But this number should certainly be increased, since the last two digits -59 concerning munifices in the line 28 and its hundreds (perhaps even thousands too) should be considered within this total."

Assuming that there is only one missing digit for the hundreds - and not two for thousands of munifices! - the legion can be calculated as between 1272 and 2072 men.
Nathan Ross
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Nathan wrote:
No - this is often misquoted.
 
Many thanks for correcting this. I can now ignore this reference.
 
Nathan wrote:
The cavalry unit is also ten subunits, each of 28 men (4x7 formation) plus ordinarius, nco and vexillarius.
 
I have found that a good test to valid the size of a cavalry unit is to create with cavalry lanes with the centuries of infantry to determine if the size and frontage of the cavalry unit is able to pass through the cavalry lanes. After all, a legion is a conglomeration and arrangement of mathematical shapes.
 
As to my dilemma of whether cavalrymen were taken from each cavalry squadron to form the guard cavalry, solved that problem yesterday. That doctrine does not apply to the Late Roman army. I feel like a huge thorn in my side has been removed.
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(01-18-2020, 11:25 PM)Julian de Vries Wrote: I have recently found a new fragment that is useful for calculating the size of the Roman army in the 6th century in this book called: Theophilus of Edessa’s Chronicle and the Circulation of Historical Knowledge in Late Antiquity and Early Islam. Robert G.Hoyland. 2011.

Theophilus was perhaps born in 695 AD and died within a few days of the Caliph Mahdi (775 – 85). His chronicle presumably starts in 590 AD and stops at 754-55 AD.
His chronicle has not survived the times, but there are others who have quoted him.

Here is the new fragment which can be found in the Chronicle of 1234. (And perhaps Michael the Syrian (MSyr: very similar to the account in Chron 1234.))

(Page 51 For the year 590-591 AD)

Msyr 10. XXIII. 386 – 87 / 371 – 72.
Chron 1234, 216 – 217

Chron 1234: When Maurice received Khusrau’s letter, he convened an
assembly of leading Romans and ordered the letter of Khusrau to be read
out loud. Then he sent John, (34) the general of the division of Thrace, with
an army of 20,000, and the general Anastasius (35) with 20,000 men from the
Armenian and Bucellarian (36) divisions.

34 Presumably the John Mystakon who Theophanes and Theophylact Simocatta (4.15.2 - 4) and Sebeos (77) say was sent by Maurice to help Narses in recovering Khusrau’s kingdom. He would seem to have been commander in Armenia at the time, though he had previously been a commander in Thrace; see PLRE , Ioannes qui et Mystacon 101.

35 A mistake for Narses according to PLRE . ‘Anastasius’ (at the end of the list after Anastasius 4T).

36 Bwql’ryw: from Greek boukellarioi , meaning privately hired soldiers rather than state recruited troops, though the term came to designate, perhaps already by the seventh century, an elite unit of the Opsikion army ( ODB , Boukellarioi). Bar Hebraeus, CS, 92, probably wrongly, writes bwlgryw/ ‘Bulgarians’.

A little more information:

Warren Treadgold says (Byzantium and its Army p.28): The Opsician Theme backed another revolt in 766, when it was probably punished again by having its eastern half made into a new Bucellarian Theme, first mentioned in 767. (30) (30. Theophanes, 438 and 440.)

According to Treadgold the Army of the East had 20,000 men in 531 (Procopius Wars , I.18.5.)), reinforced by 15,000 men called Federates by Tiberius in 577 (578) AD. (Theophanes, A.M. 6074, p. 251). The Army of Armenia in 530AD had half as many soldiers as a Persian force of 30,000, so 15,000 men. (Procopius, Wars, I. 15.11).

Treadgold guesses additionally that the Army of Thrace had 20,000 men and the two Praesental Armies also each 20,000 men.

On page 24 Treadgold says: The one source to date the creation of the themes attributes it to “the men after Heraclius,” an apparent reference to Constans II and his advisers. (The reference is in Constantine VII, De Thematibus, p.60.)

Now we can interpret the primary source.

First of all, there was no Buccelarian theme during the reign of Maurice. Did Theophilus conflate this with one of the Praesental Armies? We can also ask what does he mean by ‘the division of Thrace’? This division could be the Army of Thrace, but it might also be, in hindsight of the Buccelarian Theme, the so called Thracesian Theme in western Anatolia.

Did Theophilus transpose the Theme System of his own day on the original source?

Whatever the case might be, this fragment is an important piece to reconstruct the Roman Army in the sixth century.

There was no Theme system in Theophilus' day, there may never have even been one at all. Current scholarship by Haldon, Consentino, Zuckerman, and Pringent don't place it until after the Vexations of Nikeforos I in 811.

The army of Thrace by this time was fulfilling the role of the old Praesentalis I army it seems. It had been sent to Africa and Italy under Belisarius and was sent East against Persia. It would become the Thraekesion after the failed attempt to retake Alexandria in 642, but Theophilus does seem to at least be partly transposing. Although you are right that the various Bucellarii get formalized into a "Guard Unit" as part of the Obsequium (the old Praesentalis I and II armies) in the late 6th or early 7th century (I have to check exactly when).
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For anyone interested, Fatih Onur's article from Gephyra 14 (2017), is available on Academia.edu:  The Anastasian Military Decree from Perge in Pamphylia: Revised 2nd Edition.
aka T*O*N*G*A*R
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I know this is an old thread, but as a new user I figured I'd throw my hat into the ring on the subject of late Roman unit sizes (also I tried to post a new thread but it hasn't appeared yet, so I'm hoping it will appear hear). Based on the 1245 officers and men listed on the Perge Inscription, and the fact the legion has 2 Tribunes and 20 Ordinarii as opposed to the 6 Tribunes and 60 Centurions of the Principate Legions, my guess is that the new Legions that were fielded post-Constantine were 1/3rd the size of the predecessors. 

The 120 Augustales and 200 Flaviales can be divided with 6 and 10 per century respectively; these could be divided into two contubernia of 3 Augustales and 5 Flaviales each. The 136 Torquati can be divided into 17 8-man Contubernia, with all but the last 3 centuries having one, while the 256 Bracchiati can be divided into 32 8-man Contubernia, with each century containing at least one. Adding the 59 Munifices, this gives us 771 officers and men accounted for with 829 remaining. The 20 Armaturae Semissales could be added to the ranks with the other '1.5 annona men' (ie Torquati, Bracchiati), and 9 more can be found by adding the Beneficarii, Mensores and Librarii, and the remaining 800 can be added to the 59 on the inscription to give us 859 Munifices. 

The Ordinarii and Armaturae Duplares would be assigned at a rate of 1 each per century, while the Optiones, Signiferi, Imaginiferi and Vexillarii could be assigned at a rate of 1 each per 2 centuries, giving us 10 'maniples.' This leaves a Legion 'staff' of 2 Tribunes, 8 Cornicines, 4 Tubicines, 2 Buccinators and 1 Praeco, plus the 73 Clerici et Deputati, the 50 Veredarii and the 225 Veredarii Alii. The Veredarii Alii could be divided into 5 Turmae of 45 men divided into 5 9-man files, while the Veredarii can be divided five ways with 10 per Turmae; 5 Veredarii could be assigned as 'file leaders' giving us 5 10-man files per Turmae, with the other 5 Veredarii being a headquarters group with a Decurion, 2 deputies, a standard bearer and a musician. 

Organizing the Veredarii into 5 Turmae would allow a Clerici/Deputati to be assigned to each Turmae, and the remaining 68 can be assigned to the rest of the Legion at a rate of 2 per Ordinarius and Optio. and 4 per Tribune. Excluding supernumeraries, this Legion can be organized into 20 80-man centuries, 10 160-man 'maniples', and 5 320-man cohorts, with the 5 Turmae allowing each cohort to be supported by it's own squadron of cavalry if necessary. The 2 Tribunes can also divide the Legion equally between them, into two 800-man units of 5 'maniples' each.
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Interesting posts, which for some reason I've only just seen today (along with a lot of older stuff dating back to January!)

I've answered in your dedicated thread though, here.
Nathan Ross
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(03-17-2024, 08:29 PM)Nathan Ross Wrote: Interesting posts, which for some reason I've only just seen today (along with a lot of older stuff dating back to January!)

I've answered in your dedicated thread though, here.

I appreciate the reply; I couldn't see any of my posts or threads, so I wound up reposting some info I'm afraid!
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