Roman Military Service during the Principate

[Monad]

I keep coming across academic works that claim a soldier served for 25 years. In 13 BC, Augustus decreed all legionaries must serve for 16 years and all Praetorians for 12 years. In 5 AD, Augustus lengthened the term of service of the legionaries to 20 years.

The Codex Justinianus (12 35.2) mentions: "if you have completed twenty years' service, sordid military fatigues will not be imposed on you," which hints at the military service being longer than 20 years. There is epigraphical evidence of soldiers serving 21 years, 22 years, 25 years, and 26 years. Tacitus reports that men still served in the army for 30 year and 40-year periods, as does the inscriptions from Virunum in Noricum, belonging to cohors Montanorum prima, which records 30 years' service, 36 years, and 40 years.

I am baffled as to how some academics, well, nearly everyone I have read, has settled on 25-year service as the standard. Is there some reference I am missing that I need to know about, or is this period of 25 years, just the new theory?

Your help would be appreciated.

[Jim Webster]

I've read the bit where if you serve twenty years you no longer need do fatigues.
Also I have wondered just how many man in a unit over a certain length of service were combat soldiers and who instead had learned and were working on useful trades and similar.
After all, if you're a man in his later forties, with a woman and children in the vicus, working as a blacksmith, at a forge provided by the army, with fuel provided by the army, metal provided by the army, and a constant string of 'foreigners' done for mates and paying customers, why would you leave? OK, take the cash bonus, buy land, and have tenants farm it, whilst you stick with the job you know

[Erpingham]

The wikipedia article on the Roman army dates the raising of legionary service to 20 years, plus five in reserve, to AD 5.  The reference is Cambridge Ancient History, vol IX, p. 376. From looking at the references, I think this is a mistype for vol. X, p376. This would make the article referred to

Keppie, Lawrence (1996). "The army and the navy". The Augustan Empire (30BC - 69 AD). Cambridge Ancient History (CAH). Vol. X. Cambridge University Press. ISBN 0521264308.

Presumably Keppie gives his source there.

[Duncan Head]

Interesting question.

The general view seems to be that the required term of service increased from 20 years to 25 during the first half of the first century, but like Steven I can't see a specific source cited anywhere. Thus Brian Campbell, in The Roman Army 31 BC - AD 337: A Sourcebook, p.20 "However, by the mid-first century legionaries and auxiliaries served for 25 years".

What we do seem to have is a lot of auxiliary diplomata specifically recording that the discharged auxiliary soldiers "have served 25 or more years" (for example items 323, 324, 325 (which actually says 26 years) in Campbell's book cited). This does seem to imply that 25 years was the required length of service that entitled auxiliaries to discharge and citizenship.

Legionaries don't get diplomata but Campbell's item 329 is a papyrus concerning some Egyptian veterans of Leg. X Fretensis seeking a letter to confirm their discharge having "conducted ourselves over twenty [years] in ever respect as good soldiers should". The problem here is that they say they were recruited in (the equivalent of) AD 124-5, but the document's from AD 150...

The 30 or 40 years in Tacitus Ann. I.17 seems to be being complained of as an abuse of the system, not as a rule.

[Adrian Nayler]

The wikipedia article on the Roman army dates the raising of legionary service to 20 years, plus five in reserve, to AD 5.  The reference is Cambridge Ancient History, vol IX, p. 376. From looking at the references, I think this is a mistype for vol. X, p376. This would make the article referred to

Keppie, Lawrence (1996). "The army and the navy". The Augustan Empire (30BC - 69 AD). Cambridge Ancient History (CAH). Vol. X. Cambridge University Press. ISBN 0521264308.

Presumably Keppie gives his source there.

There are two relevant passages authored by Keppie in volume 10 of the Cambridge Ancient History:

Firstly, page 377
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Secondly, page 391
You cannot view this attachment.

Keppie's source, alluded to by Anthony, seems to be Cassius Dio, Roman History LV.23.1 (translated E. Cary)
"The soldiers were sorely displeased at the paltry character of the rewards given them for the wars which had been waged at this time and none of them consented to bear arms for longer than the regular period of his service. It was therefore voted that twenty thousand sesterces should be given to members of the pretorian guard when they had served sixteen years, and twelve thousand to the other soldiers when they had served twenty years."

The common citation of 25 years service may thus be a summation of 20 years active service plus 5 years in the reserve or possibly a conflation with the length of service to achieve citizenship for auxiliaries from their diplomas (or both  ).

[Monad]

Thank you to all that have responded. It has given me clarity.

Duncan wrote: The general view seems to be that the required term of service increased from 20 years to 25 during the first half of the first century, but like Steven I can't see a specific source cited anywhere.

Thank you, Duncan. That is reassuring to know.

Duncan wrote: This does seem to imply that 25 years was the required length of service that entitled auxiliaries to discharge and citizenship.

Agreed.

Adrian wrote: The common citation of 25 years' service may thus be a summation of 20 years active service plus 5 years in the reserve.

That is my calculation as well. Up to 20 years for the legionaries, and then another five years as veterans or reserves.

There is a reason as to why the years of service is important to me. In his description of the levy of the four legions, Polybius mentions batches of four men at a time, which I have been able to identify as representing the number of campaigns a soldier has undertaken in the past. The 16 years' service and then 20 years' service are divisible by batches of four men, so the system Polybius is describing appears to be still in use. The campaign division a soldier is presently undertaking determines where he is stationed in the century when on the battlefield.

Many of the data for the principate is starting to highlight what the Romans could be up to. In 35 AD, the legate Marcus Trebillius, with 4,000 legionaries and a picked force of auxiliaries suppressed a revolt in Cappadocia. (Tacitus (The Annals 6 41 1).

Those 4,000 legionaries are missing those 1,000 legionaries with the lowest years of service (service division). For the campaign against the mutineers in Pannonia in 6 AD, 10,000 veterans and 10 legions were levied. Paterculus (2 113) The 10 legions and 10,000 veterans can allocate each legion 1,000 veterans. What this is showing to me is that when on campaign, each legion leaves behind those 1,000 troops with the lowest service division (1,000) as garrison troops or camp guards. Each of the 10 legions replaces them with 1,000 veterans, thereby ensuring the legion is at full strength.

Leaving the less experienced troops as garrison troops began in the First Punic War when sending fleets to Africa. The practice continued in the Second Punic War as well.

While campaigning against the Tiridates in Armenia, the Roman commander Corbulo posted his allied infantry and auxiliaries on the wings, while the sixth legion occupied the centre of the battleline. The sixth legion had been reinforced with 3,000 men from the third legion that had been summoned from another camp to give the appearance the sixth legion looked like a single legion with one eagle. Previous to this, Tacitus reports that Corbulo had divided his strength and set up camps at widely separate points. Tacitus (The Annals 13 37-38) This is a completely different method of garrisoning and does not involve the troops being separated by the years of service division.

At this present moment, Arrian's expedition against the Alans also looks like those troops with the lowest experience in the 12th legion being left at the legionary camp. Arrian (26) also describes the legionaries as being arrayed in four taxis, and by removing the least experienced also from the 15th legion starts to fit this criteria. Still, need more work on this before I can be certain.

[Monad]

The results are in, and I am very jubilant. Arrian's legions for his campaign against the Alans has definitely omitted the lowest experienced troops for the campaign. After omitting the lowest experienced troops, the legionaries are then formed into four bodies, two large bodies and two small bodies, each of differing sizes. Arrian, for his campaign, takes one large body (15th legion) and one small body (12th legion). The remnants of the 15th legion (small body) and the 12th legion (large body), protect the legionary camp, and have the same number of men as Arrian's large body. Arrian's legions are using the legion's numerus organisation, which amounts to nine numeri.

In order to put pressure on my findings, I compared Arrian with my research on Hyginus' camp. Ok, I may be wrong, but it all works to perfection, that is Arrian's campaign against the Alan and my exploration of Hyginus camp, which part of explains how the campaign divisions are allocated which tents. The contubernium organisation, believed to be the tent arrangement is also part of the century organisation, meaning the men from the same tent stand in close proximity to each other in the century when marching or when in battle order. This is extremely important to know, as it helps to understand how Arrian's four men wide formation works when on the march. It has to be able to face any direction when on the march to a threat and still have the men with the most campaign experiences in the front ranks facing the enemy. This order is established in the tenting arrangement of the century. This order is established the moment the men walk out of their tent and assemble in front of their tent.

When describing the layout of an ala milliary in the camp, Hyginus writes: "A milliary cavalry squadron should get 150 feet in breadth and 600 feet in depth. By this reckoning, 150 feet produces <five> half strips. A cavalryman gets 3 feet along the length of 600 feet; I will take a third of this [i.e. of 600], so that I have the number of cavalrymen who will camp along that length: this is 200, so this will be [the capacity] of one-half strip; and now we stated five half-strips: 5 times 200 is 1000, the space for a milliary cavalry squadron." Translated by Duncan B. Campbell.

Following Hyginus that each man is given 3 feet, this means the length of 600 feet can accommodate 200 men. However, Hyginus takes a third of 600 feet, ends up with 200 men and multiplies by five half strips to arrive at 1,000 for a milliary cavalry squadron. However, 600 feet divided by three equals 200 feet, and when 200 feet is divided by each man having 3 feet, the result is 66 point 66 men. Now the correct number of men in a cavalry milliary, which omits the officers, is 960 men

https://www.academia.edu/124417625/An_Ex...to_Hyginus

When 960 men is divided by three = 320 men, and when 320 is divided by 5 half strips = 64 men. Also, 960 men divided by 5 = 192 men and when multiplied by 3 feet per man = 576 feet. Therefore, Hyginus' 600 feet in length has been rounded from 576 feet. Now, just by looking at it, 192 men is not divisible by 10 men per tent, but is divisible by 8 men per tent, so 192 men divided by 8 produces 24 tents, and when the 576 feet is divided by 24 tents, each tent is allocated 24 feet as per Hyginus. At this point Hyginus has rounded the 24 tents to 25 tents, because 25 tents x 8 men per tent is able to house 200 men, and 25 tents x 24 feet = 600 feet as per Hyginus.

As shown above, the problem with Hyginus is that in some examples he rounds up or down the number of tents, which thereby produces the wrong number of men. When corrected, Hyginus provides a wealth of information, that I find breathtaking. I didn't realise it at the time that the examination I made of Hyginus' camp would be so beneficial to understanding Arrian's expedition. It has reshaped my investigation into the legion of the principate, especially in relation to the infantry and cavalry formations. For me, it has solved Arrian's (20) statement "let the entire cavalry stand deployed by troops and basic units eight [deep] next to the foot soldiers." Translation by DeVoto. Campbell's translation has eight [companies], which I cannot make work. Also, Arrian's (5) allocation of five centurions for the first cohort of the 15th legion is correct.

And the reason why the 15th legion was "more numerous" was because they would provide the protection for the baggage train, thereby leaving eight numeri of legionaries to face the Alans.