Roman Military Diploma On-Line
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Part 1  Introduction To Roman Military Diplomas

Roman Military Diplomas / Diplomata (or better citizenship and/or military discharge certificates) are in some way the "greencards" of Roman times (green also being the dominating color of their bronze patina). Only that today you can win citizenship in a lottery. In Roman times foreigners had to serve for minimum 25 years (army) or 26 years (fleet) or longer in the auxiliary military forces (infantry = cohors,  infantry mixed with light cavalry =cohors equitata, heavy cavalry = ala, fleet = classis, or pretorian cohors). In contrast the Roman legions (up to ca. 30 elite units mainly distributed along the borders of the empire, of ca. 5000 "legionaries" each) were reserved for Roman citizens. This distinction is thought to have lost its importance when Caracalla granted Roman citizenship in the early third century to all living in the Roman empire (except to the slaves of course), known as the Constitutio Antoniniana of 212 AD.

Roman Military Diplomas (more than 1000 are known to us and published to date) were/are found all over the Roman empire, mostly but not exclusively in the border provinces. As Diplomas show also the origin of the recipient, we can see that the middle and lower Danube region was a major recruitment area for non-citizens into the Roman auxiliary forces in the first and second century AD. While some veterans seem to have stayed close to their last place of service, many veterans - especially from the Danube region - seem to have returned to their home provinces after serving all over the vast Roman empire (we can conclude that from diplomas whose find spot is known). But there is no clear rule, a diploma could be found anywhere in the Roman empire, regardless of place of origin or service.

The massive barbaric invasions in the third century AD destroyed many Roman settlements, some never to be inhabited again, thus conserving diplomas that would otherwise have been melted down eventually for their metal value. Still only a fraction of < 1% of issued diplomas seems to have survived.

What is a Constitution ?

A constitution is a legal document issued by the Emperor in Rome. In case of Roman Military Constitutions the emperor granted Roman citizenship to specific veterans and their families, after a long and honorable service.

The legal process is thought to have been...:
1) The office of the Commander of an auxiliary unit lists all those soldiers of his ala or cohors ready for retirement or deserving citizenship
2) He sends the list to the governor of his province
3) The provinical governor's administration bundles all such requests for that province
4) and sends the list for this province to Rome 
5) The imperial administration office in Rome draws up an imperial constitution for that province to grant citizenship to all the veterans on the list
6) The emperor personally approves and grants the rights
7) A large bronze plate is written up listing all included veterans and placed publically in Rome (ie at the Minerva Statue behind the Divus Augustus Temple)
8) Individual bronze copies (diplomas) are written in Rome for each veteran with his name (possibly but not likely at cost of the veteran)
9) The copies are checked, confirmed, wired, and sealed by 7 witnesses
10) The diplomas are sent to the governor in the province (more likely than sending them straight to the unit)
11) Diplomas for a specific unit are sent on from the Provincial capital to the unit commander
12) The unit commander hands out the diplomas to the veterans (likely in some sort of a ceremony)

We have published recently a diploma from an auxiliary constitution issued for only two veterans, a centurio and a horse soldier ! But mostly we are talking of veterans from anywhere between ca. 4 and ca. 25 auxiliary units, depending on the specific need of that province at that time. Sometimes more then one constitution was issued for the same province at the same date (split by units for logistical reasons ?). Thus potentially hundreds of soldiers at a time. Same for a praetorian fleet.

How many diplomas would have been issued for a given unit on a single date ? Let us take a regular cohors, 500 men, each serving 25 years. That would be 20 veterans each year assuming yearly recruitment (not always the case, see below) and no deaths (depends on circumstances). Or 40 in a milliaria unit of 1000 men.  More real life scenarios show however that a major crisis like the Bar Kochba uprising caused major casualties, mass recruiting shortly after to fill the ranks, and multiple diplomas ie for the neighbouring province of Syria 25 years later. In similiar circumstances we know of 10 or more diplomas surviving of the same constitution indicating such a massive "bolus" of discharge.

A constitution could have covered thus between one and several hundred soldiers.

Constitutions are known to us only through their personalized copies = diplomas. Not a single of the large bronze plates from Rome survived. Below image shows a possible fragment of a constitutional tabula from Rome listing all the soldiers of a province that received Roman citizenship. It was re-used as a military diploma later on. (The "new" side with the diploma text not shown)

Possibly the only surviving fragment of a constitutional tabula (re-used on the other side as a military diploma later on), Weissenburg Museum, Germany

How many constitutions do we know ? More than 400 Constitutions have been identified to date, with more than 1000 surviving individual military diplomas, some complete, but most in small fragments. 

Which Units Received Citizenship Constitutions ? How many do we know ?

Constitutions cover mainly auxiliary forces and provincial fleets for non-citizen troops based along the the frontier. Survival of diplomas is more likely in provinces with many units - we only see a small fraction of what has been issued back then, maybe as little as 0.3 %, which is not surprising considering that bronze was a valuable and easily re-usable resource. For example we know more constitutions for Moesia (inferior and superior), Pannonia (inferior and superior), Dacia, Raetia, Germania, Britannia, and Mauretania Tingitana than for provinces with only small military presence such Thracia or Sardinia. 

Constitutions are also known for the praetorian cohorts, the emperor's horse guard, and for the praetorian fleets in Ravenna and Misene. Below two graphs showing all known Roman citizenship constitutions as of December 31, 2014, first for the provinicial auxiliary forces incl the Equites singulares, and in the second graph the Fleets, the Praetorian and Urban Cohorts:

Known dated Roman Citizenship Constitutions per Roman Province (often with multiple surviving military diplomas)

as of Dec 31, 2014

Known dated Roman Citizenship Constitutions per Roman Fleet, Praetorian Cohort, Equites Singulares, Urban Cohort (often with multiple surviving military diplomas)

as of Dec. 31 2014

The earliest known diplomas are from the reign of Claudius, the latest of the Tetrarchy. Most common are those of Antoninus Pius, also Traianus, and Hadrianus (see below graph). Bronze diplomas were found for almost every year between the middle of the 1st century and mid 3rd century AD. We know however of two periods, one during the Germanic invasions under Marcus Aurelius and the other during the crisis after Gallienus to the Tetrarchy, where not a single (bronze) diploma survived. Why ? Werner Eck, David Macdonald, and I have speculated in a recent article that this could be due to bronze having been too costly in these periods of crisis, possibly combined with less discharges due to a high number of casualties in war and disease like the plague epdiemic reported in that period. Thus the practice of issuing constitutions and diplomas would have continued, but less being issued and on other perishable materials. We know ie of certain privileges to soldiers found in Egypt written on wood or papyrus. But if these were official documents like a bronze diploma remains unclear. Still the hypothesis that the issue of diplomas was a regular process, for all provinces, every year as needed, and for all veterans, is making a lot of sense.

Number of surviving Roman Military Diplomas by Emperor

Emperors on diplomas
as of 2007

What does a Roman Military Diploma look like ? 

A complete diploma consists of 2 bronze plates of rectangular shape, between 10x12 and 21x16 cm depending on the period, with text on both sides, bound together by bronze wire and sealed with witnesses seals. The seals were covered by three bronze strips to protect them from mechanical wear.

Below a typical diploma, unwired and opened up, with preserved witness seals and their protecting metal cover (closed and opened). This particulary well preserved example was found in Slavonski Brod and had been issued under Vespasianus.

The outer side of the so called tabula 1 holds a copy of the complete text. The outer side of tabula 2 (right) lists the seven witnesses and holds the seals. 

(The images below are from the Slavonski Brod Website). 

Below image shows the seals exposed

The two inner sides of the two tabulae together reflect the outer text of tabula I, sometimes abbreviated and often the text is written less carefully than on the outer sides. There is the hypothesis that the actual copy of the Constitution in Rome is the inner - protected and sealed - text, while the outer text was for daily use. The fact that the inner text got more and more neglected shows that this seems to have been forgotten over time, maybe because the inner text was rarely ever exposed

Another complete auxiliary diploma, still wired together (seals and their cover are lost)

From MARCUS AURELIUS & his son COMMODUS, 23 March, 178 A.D., under the consulship of Sergius Scipio Orfitus and P. Velius Rufus, Britannia under the governor Ulpius Marcellus, to the cavalryman Thiophorus, a Dacian of the VII Thracian cohort, under the command of Ulpius Marcianus. (from the Axel Guttmann collection)

Why twice the same text ? The outer side was for daily use. If there was any suspicion of fraud, Roman provincial officials could break the seals and compare the outer with the inner text, compare for manipulations without having to wait for confirmation from far away Rome. Suetonius describes this practice for important documents in the Nero text of his 12 Caesars Book.

The thickness and weight of diplomas differs considerably, as does their size. Early and late pieces are usually thicker and heavier, and more carefully written. Under Antoninus Pius, with the quantity of known diploma reaching a peak, the quality seems to have deteriorated. Late diplomas are occasionally made from pre-used bronze plates, the original text still being visible in traces.

Diplomas were handed out to the veteran in his province as proof of his honorable service, his newly granted Roman citizenship for himself and his children. One cannot rule out that the veteran had to pay for his bronze diploma, and that not all veterans were willing or able to do so. But there is no indication at all that this may have been the case. And considering the central importance of the army and the fact that this privilege was given after a lifetime of honorable service, I personally see no reason not to believe the emperor took care of the cost for bronze. Still the fact that we find more diplomas for horse soldiers - presumably better paid - could be indicative for this hypothesis. But maybe horse soldiers simply had a better chance for survival ?

What is the Legal Text ?

All diplomas follow the same scheme, with sectors of standard legal text and sectors with individualized text.

Auxiliary Diplomas:

Structure of the text:

Imperial titles defining the Emperor and the year of his reign - The imperial title are though to reflect the moment of the imperial decree:

The list of the units covered by this constitution: The province and the governor: Citizenship legal text (varied over the centuries): Below an example of an inner text of a tabula II from the Munich Archeological Museum, for the Helvetian soldier Cattus, son of Bardus, and his wive Sabina, his son Vindelicus, and his daughter Materiona:

The date (day and month) and the year are defined by the two consules - though to reflect the day of issue of the diploma:

Recipient part of the diploma: Legal text stating that this is a witnessed copy of the original constitution in Rome: Fleet Diplomas:
Similiar to above, just that there is obviously no list of units, but only the name of the fleet. The commander of the fleet replaces the governor, sometimes the name of the captain of the ship is mentioned as commander of the unit. 26 years of service, later more was required.

Praetorian, Urban Cohorts, Equites Singulares (Imperial Horse Guard), Legio I and II Adiutrix Diplomas:
Similiar to above, just that the single unit named is one of the the pretorian cohorts or another Italian based unit.

Another still wired diploma, shown is the side with the witnesses (Munich Archeological Museum)

What was the Importance of the Diploma for the Veteran's Family ?

Auxiliary diplomas from Claudius to the early 140s also name the veterans wives and kids if they had any and the legal text covers not only the veteran, getting Roman citizenship, but also his family.

Legal constraints need to be considered here:

The Veteran received however in the diploma the right to marry officially (conubium) a foreign woman without Roman citizenship (but only one and only once). The veteran's possible inoffical liaison with such a woman was thus legalized, she herself did not get Roman citizenship. Such women can be found on diplomas with their father's name and their place of origin. For unknown reasons very few wives are specifically mentioned on auxiliary diplomas after the early 140s, maybe because more and more veterans were able to marry Roman citizens even in the provinces, offspring from other veteran families.

Children to such an inofficial  relationship were only named on diplomas until ca. 140 AD, afterwards only children born after the military service were included in the legal text (but of course were born too late to be named on the diploma). As exception to the rule we still  -rarely- find diplomas with special legal formulas that continue to name wives and kids,  but only for officers (centurios or decurios) with families they had "registered" with the governor before they entered service. After their service they then got the privileges and the kids were named on the diploma. There is strong evidence that this privilege was not always restricted to officers, but also offered to common soldiers. Not many cases though, most common soldiers will have been too young anyway when enlisting to have qualifying families.

And we know of at least one diploma where Roman citizenship was also granted to the parents and siblings of the soldier (the soldier continued service as Roman citizen to complete his 25 years), but no wives and kids are mentioned - Eck & Pangerl, Chiron 33, 2003, 347ff

Questions that remain are:

1. Why were children no longer included after 140 AD ?
2. Why did diplomas continue beyond the widening of the Roman citizenship under Caracalla for Praetorians and Praetorian Fleets,  but not for Auxiliary soldiers ?
3) How about the Roman citizen soldiers serving in the Legions ?

To question 1 we can assume that the number of such children may have increased substantially, and maybe Antoninus Pius simply wanted to clarify situation unfair to the Roman legions, citizen soldiers for whom we are not aware they got the same privilege of legalizing their inofficial mistresses and offspring (see question 3).

To question 2 there is no 100% satisfying answer.
Why would Praetorians, and fleet or auxiliary soldiers already Roman citizens (either by birth or after Caracalla's widening of the citizenship in 212 AD) still benefit from a military diploma ?  If they married a Roman citizen girl, they certainly had no need for a diploma.
During the 1st and 2nd centuries - before the wider impact of citizenship grants to veterans created a sufficient supply of women with Roman citizenship even in the remotest limes areas - a soldier was likely to marry a non-citizen woman, a foreigner or a freed slave woman. And as we learned above Roman citizens could not have a formal marriage with non-citizens, and their children did not enjoy the full status of a Roman born. Thus as long as there are non-citizen women to marry, a diploma would make sense, at least for some.
The termination of auxiliary diplomas around 203 makes somewhat sense in this context. Soldiers could marry during Septimius Severus, and all free inhabitants of the Empire became Roman citizens anyway during Caracalla. All men were Roman citizen anyway, and there were no more foreign women to marry. So far so good.
But auxiliary diplomas became already increasingly rare already much earlier - after Antoninus Pius (see graph above). And we still find Praetorian and fleet diplomas after 212 AD. Actually more than ever. Most Praetorian and Fleet diplomas we know of were issued after Septimius Severus / Caracalla and fall under this paradox. Why would veterans still want a diploma ? Honor ? Still for their foreign wives from outside of the Roman empire ? Or were the Praetorians of that period we know of mostly coming from outside the Roman borders ?  No, most were born in cities in the balkans, from inside the Roman empire. Hard to explain !
There must be a reason for this we can only speculate about. Maybe we misunderstood the widening of the citizenship under Caracalla and it was much more restrictive ?

Thirdly the question about the legionaries, all Roman citizens, but who might have also enjoyed a marriage with a non-citizen woman, but who seemingly never got diplomas. And let us remember most legions were also stationed at the borders with a chronic undersupply of Roman citizen girls (see above). Still the only legionary diplomas we know are from the civil war of 68/69 AD for soldiers of Legio I and II Adiutrix formed out of auxiliary non-citizen fleet soldiers, who needed to be quickly "Romanized". No good answer here either.

Why do we find so few diplomas ?

The number of diplomas issued must have been in the 100,000s over the centuries, but we have so far only found fragments of a good 1000, far less than 1 %.
Why ?
Bronze was a costly resource that could be readily reused, either by melting it down as scrap metal, or by finding other use. Some examples below:


Not all that is bronze and carries a military discharge text is a citizenship diploma...

A Military Discharge Diploma
not granting citizenship and not officially witnessed and sealed (likely private copies of official documents in perishable materials such as wood/wax/paper)

under Philippus I and II, from the RGZM Mainz, only one side with text, likely a private bronze copy of a letter


Dont' confuse a Military Diploma with other Texts on Metal Plates....

Curse Tablets

Lead plate with curse, magic signs... Munich Archeological Museum

Other Official Documents

IMP(eratori) CAESA RI AUGUSTO P(atri) P(atriae)
(from the Axel Guttmann collection)