Shrinking of Roman Legions

[Timotheus]

I know in the late Empire that the Legion was reduced in size from about 5000 men to 1000 men.

I also know that the idea was that smaller legion units could be dispatched to more areas to deal with the growing number of small problems in the Empire or the incursion of small nomadic groups from Asia.

Do we know of an primary sources though that state this or is it all an assumption?

[Jona Lendering]

I think it is a modern assumption. AFAIK, Gibbon is the first to have raised questions (in his description of the siege of Amida), which is interesting, because it means that he did not find it in his usual source of knowledge, the books of the Maurists. So, I'd say it was Gibbon who first realized that the size of the legions had decreased.

[D B Campbell]

Gibbon ... did not find it in his usual source of knowledge, the books of the Maurists.

Interesting. I had the impression that Gibbon was mostly critical of "modern" sources (Voltaire, for example, he damned with faint praise) and worked mainly from the primary texts. But I have never looked at his later books, where (I believe) he leaned heavily on Barthélemy d'Herbelot de Molainville.

[Timotheus]

So it can be inferred that the legions shrank in size but we really dont know for certain who made the change and what their reasons for doing so?

[Tiberius Clodius Corvinus]

I'm no expert on this, but AFAIK this formal change reflected only a transition what had already happened in practice.

I also know that the idea was that smaller legion units could be dispatched to more areas to deal with the growing number of small problems in the Empire or the incursion of small nomadic groups from Asia.

I think it had been common for a while before the "official" shrinking to split the classical legions and deploy strong vexillations whereever needed. May be these detachments were the nucleus of the later micro legions? :?

[D B Campbell]

The book you need is T Coello, [amazon]Unit Sizes in the Late Roman Army[/amazon] (BAR-S645, 1996).

Coello concluded that the creation of so many new legions under the Tetrarchy suggests that they must've been smaller.

I'm inclined to follow H.M.D. Parker's theory (Journal of Roman Studies 23, 1933), that the new legions were full-strength, so that Diocletian could fragment them by drawing off vexillations for service elsewhere.

Ultimately, the legionary garrisons were smaller, because they were fragments of the original units ("mini legions"). That's why we find the same legion in several different locations in the Notitia. And that's why late legionary fortresses like El-Lejjun (4.6ha) are so much smaller than earlier fortresses like Lauriacum (22ha).

[L C Cinna]

This question partly touches my diploma project which deals with the ruling practice of Gallienus but also touches his, so called, army reforms.

I'll keep this short for now as I'm still digging through sources and stuff and my research is not yet complete.

You surely know that the usual practice was to send vexillation to the areas of operation. So the legions only sent part of their troops to a place where a campaign took place while the rest stayed in their bases. This practice worked well until the crisis of the 3rd century.

Note that I haven't researched the further development of those detachments after the reign of Gallienus so this is all just a guess.

During the reign of Gallienus the situation after 258 is like this:

Valerian had taken troops with him to the east and we have fighting and incursions all along the western boarders from the Rhine to the Danube. During his early campaigns along the Rhine Gallienus seems to have operated with a relatively small army consisting of detachments which make up his "field army" (it's not a standing one like in the later empire). He seems to have moved from one area of crisis to the other with those troops (suggestions are Praetorians and Legio Parthica plus others) along the Rhine and used them together with the troops stationed locally to fight the Alemanni and Franks.

Because of the many problems along the boarders it seems like it was not possible to extract whole forces and remove them from their local bases as this would have made incursions even easier.

Then we have 2 usurpers in the Danubian provinces. Gallienus combines vexillations from the Rhine to march to Pannonia. Vexillations from Britain seem to have replaced the troops which marched with him (parts of several of the Rhine legions). He defeated the 2 usurpers (the 2nd was a result of the failure of the 1st) and inscriptions suggest that he stationed parts of the German vexillations along the Danube to reinforce the boarder pressed by Sarmatians, Goths and Marcomanni and to control the mutinous Moesian troops. They stayed there while he marched to Italy with the core of his army to defeat the Alemanni.

After the capture of his father 2 usurpations occur: the Macriani in the east and Postumus and his Gallic empire in the west. By this time it seems there were at least 5 mobile "field armies" consisting of vexillations and cavalry operating separately: Gallienus own, his commander Aureolus in the southern Balkans, Silvanus and Postumus commanded an army in Gaul and in the east Macrianus and his sons with the majority of Valerian's former army (my theory is that this army contained quite some troops which were taken east by Valerian) and another under Odaenathus.

just noticed it's a bit complicated if I try to keep it short but I'll try... :roll:

back on topic: The Macriani are defeated but Gallienus can't operate against the Gallic empire yet as there's still trouble along the Danube and here we come across a really interesting point which is connected to your question imho:

After the break-away of the Gallic empire Gallienus' Germanic vexillations seem to have stayed with him. He even struck coins to honour them but their bases and command were not under his control! He addressed only his loyal vexillations as if they were the legions. This suggests that they might have developed their own command and the smaller units were recognized as being more individual. One of his field armies was then stationed in Milan while a 2nd still seems to have operated in the Southern Balkans.

I haven't investigated Aurelian's actions yet so I can't tell you how many of the troops were transferred back after the end of the Gallic empire but the changes during Gallienus strongly point towards what develops into the later army. Note that I wouldn't consider his actions a reform (except the removing of the senators from the army) as this was not really done on purpose but out of necessity.

Anyway his tactics of spreading vexillations to reinforce certain areas leads to the later smaller legions imho. These detachments seem to have stayed in their new bases for years and it's uncertain (yet) if some of them ever did return to their original units or had developed into separate units during the 10 years of the Gallic empire.

[Timotheus]

While it would help deal with small problems all over wouldnt it reduce large battle effectiveness as the units would train together less often?

Sure when 600 nomads start to ravage the area you send one legion and its dealt with.

But when 15,000 nomads migrate to the border you are gathering alot more independent units that have not trained together that much.

Also your commanders have less large unit expereince.

[John M McDermott]

Adrian Goldsworthy discusses in one of his books that Roman armies in the late period were kept small because the Emperor could not entrust large formations of troops to anyone but himself. The reason was political: Giving control of large formations of troops to someone (even a relative) created a potential rival for the throne. Perhaps this logic applied even at the legion level. Someone who controlled only 1000 troops was less of a political force than someone who controlled 5000.

[PhilusEstilius]

There is an awful lot of truth in what you say John, for indeed was it not Vespasian who when he became Emperor changed the system of having two legions together at one fort and place. It's said that this man was one of the better Emperors, however he made it very clear at the begining he was not going to allow another civil war to come about. All to do with power and control.

[D B Campbell]

... was it not Vespasian who when he became Emperor changed the system of having two legions together at one fort and place.

Domitian, Brian.

[PhilusEstilius]

Im not so sure that I would agree on that Duncan.

[Quintius Clavus]

The subject of smaller legions in the late Roman period is part of an article in Roman Legions and their Fortresses - which I have at home. If I remember, I'll put up more information about the article/author etc.

The forts/fortresses, etc. are much smaller for the late period. The assumption is that many vexillations of the legions wound up permanently away from the parent units, which was itself greatly reduced in size as a result. Some of the units have names, which may reflect on their former parent unit.

Quinton Johansen
Marcus Quintius Clavus, Optio Secundae Pili Prioris Legionis III Cyrenaicae

[D B Campbell]

Im not so sure that I would agree on that Duncan.

I read it in an Osprey: [amazon]Roman Legionary Fortresses 27 BC-AD 378[/amazon] by Duncan B Campbell. :wink:

The assumption is that many vexillations of the legions wound up permanently away from the parent units, which was itself greatly reduced in size as a result.

Not an assumption. It's a demonstrable fact.

[Jona Lendering]

Im not so sure that I would agree on that Duncan.

I read it in an Osprey: [amazon]Roman Legionary Fortresses 27 BC-AD 378[/amazon] by Duncan B Campbell. :wink: