The Recruitment of Roman soldiers explained (Legionaries, Auxiliary troops, and Praetorian Guard)

The Roman military was one of the finest fighting forces of history. But how were these men recruited? What kind of requirements had to be fulfilled to join the Roman army and how did these requirements differ between the Roman Legions, the Auxilary troops, and the Praetorian guard.

In this article of the series about the lives of the average Roman soldier, we will find an answer to these questions!

Men who wanted to join the Auxiliary troops had to be able-bodied but didn`t have to be Roman citizens. Service in both the Legions and the Praetorian guard demanded full Roman civil rights. Additional requirements were a good physical shape, good eyesight, being at least 5.41 ft (165cm) tall, able to speak and understand Latin. And in case a man wanted to join the Praetorian guard he had to be born in Latium, Etruria, or Umbria. Recruits were mostly between 18 and 21 years old, could not have a criminal record, and had to have a good reputation.

Let`s find out more.

The recruitment process in the Roman army

For the sake of a less confusing argumentation, I will focus on the recruitment of soldiers during the time of the Roman Empire since before that, during the time of the Roman Republic, there was no such thing as a standing army. For more information on how armies were assembled during the time of the Roman Republic, I would like to recommend you my article here, especially the first paragraph.

But let`s now turn to the recruitment of soldiers during the time of the Roman Empire!

Who was tasked with recruiting for the Roman army?

During the time of the Roman Empire Rome basically controlled all the land around the Mediterranean. Needless to say that that kind of landmass called for organized recruitment.

The recruitment of Roman soldiers was called dilectus. Each recruit had to meet certain requirements that were checked at the probatio, the interview during the recruitment procedure. Usually a high-ranking man, for example, the governor of a province was tasked with organizing the recruitment. In times of particular need, for example in case of a war, plenipotentiaries could be chosen.

These plenipotentiaries had different names depending on where they were tasked with recruiting.

Plenipotentiaries who were tasked with recruiting in Italia, that’s roughly modern-day Italy, were called missi ad dilectum, if a plenipotentiary recruited in a province that was governed by the Senate he was called legati ad dilectum and if he recruited in a province that was governed by the Emperor he was called dilectator.

So after having clarified the responsibility for the recruitment process there is one logical next question. How many recruits had to be found every year to balance the losses and the retiring soldier?

How many Roman soldiers were recruited each year?

One might think that the number of recruits that had to be found each year must have been enormous.

But that was actually not true.

Especially because of the change in the Roman strategy from an offensive to a defensive interpretation during the first century AD and in combination with the length of service, more information on for how long Roman soldiers enlisted in my article here, the number of recruits was much lower than one might expect.

Each Legion needed an average of 240 recruits per year. So the total of 25 legions put the number of recruits for the Legions at 6.000 per year. The Auxiliary and the Navy each needed roughly the same number of recruits. So each year a total of 18.000 men had to be recruited from the entire Mediterranean.

Now one might think that recruiting 18.000 men each year can`t be that hard, especially not if the number is distributed over the entire Mediterranean as the recruitment area.

But finding that amount of suitable recruits each year actually proved rather difficult!

Because the annual need for 18.000 recruits could not be satisfied by volunteers additional men were drafted. The compulsory military service consisted throughout the time of the Roman Empire!

And attempts to escape the draft, for example by intentional mutilations of the thumbs were both common and harshly punished. There is actually one account where an Eques, more on the Eques and how that social class differed from the Senators here, mutilated the thumbs of his sons to prevent them from being drafted. He was actually punished by being sold into slavery and it was made sure that he would not be bought (and immediately freed) by a friend of him.

The reason why the Roman military had such a hard time finding enough recruits can be found in the requirements that recruits had to meet.

Let`s now take a look at these requirements.

The recruitment of Roman Legionaries

When we look at the requirements a man had to meet to serve in the Roman army we have to look at the Legions, the Auxilary troops, and the Praetorian guard separately.

By the way, not only the requirements to join differed between these types of units. The pay, more on that here, the retirement, more on that here, and the length of service, more on that here, also drastically differed between the Legion, the Auxilary troops, and the Praetorian guard.

Let`s now start out with the requirements a man had to meet to be allowed to join the Legions, the backbone of the Roman military.

Physical and Intellectual requirements

To ensure that each recruit was capable of finishing training and becoming a skilled soldier certain physical requirements had to be met.

Recruits who wanted to join a Roman Legion had to be…

  • Male
  • either a bachelor or any existing marriage was ended by joining
  • In good physical condition
  • have good eyesight
  • an be at least 5.41 ft (165cm) tall
  • able to speak and understand Latin
  • normally between 18 and 21 years old
  • full Roman citizens
  • have a good reputation
  • ideally a recommendation from a well-respected public figure

Additionally, recruits were examined if they could write and read since the military always had a demand for skilled soldiers who would take on administrative jobs in both the army itself but also in the provincial administration. Recruits with training as a blacksmith, a butcher, or a carpenter were also especially welcome.

So being able to read and write opened up career opportunities to the average soldier. Centurions were most likely expected to be able to read and write.

By the way, did you wonder why being able to speak and understand Latin was explicitly named as a requirement? After all the Roman legionaries were only recruited from Roman citizens so one would expect that they would be able to speak and understand Latin as the Roman language…

Well, not every Roman citizen was born in Italy. Because of the establishment of colonies with the full Roman civil right over the course of the expansion of Rome, more on why these colonies were founded and equipped with the Roman civil right here, men could actually be full Roman citizens without ever having been to Italia.

That by the way is also a difference between the recruitment of Roman legionaries and the members of the Praetorian guard. But more on that later.

Apart from the physical and intellectual requirements recruits also had to have the right legal status and a good reputation.

The required Legal status

The legal status the recruit held was also crucial for the career path he could choose.

Roman citizens from the upper class of the Italian countryside could enter the Roman army as Centuriones while regular Roman citizens could only join as regular legionaries. Men without the full Roman civil right could normally only join the Auxilary troops.

But there were exceptions to that rule. It was possible that in times with an extremely high demand for recruits the requirement of full Roman citizenship was dropped.

Could slaves (or Gladiators) serve in the Roman legions?

There were actually two incidents, the defending of endangered Illyria and the garrisoning of the left shore of the Rhine river, during the rule of Augustus during which even slaves were recruited into the Legions. Needless to say that both occasions for which even slaves were recruited into the Roman legions were extremely risky.

On both occasions, the slaves who had to join the legions were freed right before they were drafted. It is important to state that being freed did not give these men the full Roman civil right that was necessary to join the legions. These freed slaves were only recruited into the legions because of necessity and would be deployed in their own units. Additionally, these units of freed slaves were equipped with below-average equipment and always found themselves right at the frontline.

The recruitment of slaves into the Roman legions was a rare measure that was only taken in desperate situations. These slaves would be freed right before they were recruited and deployed in separate units that were poorly equipped and given the most dangerous tasks.

So I think it became clear that normally the full Roman civil right, more on who held that full Roman civil right here, was mandatory for joining the Roman legions. And that normally excluded slaves, freed slaves, and Gladiators (since these men had a servile status). You can find out more about the servile status of Gladiators and why even men who voluntarily became Gladiators got that servile status in my article here.

But apart from these legal requirements recruits also had to have a good reputation.

A good reputation as a requirement to join the Legions

And that good reputation also partially included the father’s reputation…

Roman citizens who wanted to join the Legions could not have any criminal record and neither they nor their father could have worked in certain professions (as a slave merchant for example). Adulterers were also forbidden from joining the Legions, at least during the rule of Augustus.

That last point, the prohibition of adulterers from joining the legions, might sound quite odd. But Augustus had introduced several strict laws with the purpose to uphold morality. And many of these laws were targeted at adulterers.

And Augustus was serious about the prohibition of adultery, he even exiles his own daughter Julia because she had violated these laws.

By the way, Augustus also prohibited the soldiers from marriage. There were several reasons for that that I present in my article here. Please feel free to check it out!

In addition to the physical and intellectual requirements, his legal status as a Roman citizen, and his good reputation most recruits were between 18 and 21, although some were as young as 15 and some were already in their early 30s. The actual age at which soldiers were recruited is difficult to say for multiple reasons. I discuss these reasons together with the average length of service in my article here.

Additionally, a recommendation that was given by a respected public figure could also help not only for a career as an officer but also for a career as a regular soldier. The Roman writer Plinius the Younger was quite notorious for writing quite a lot of letters in which he praised the sons of his friends or acquaintances as highly trustworthy and suitable for serving in the Roman army.

If a young man met all these requirements he was recruited into the Roman legions.

What followed were 3 steps that transformed him from a civilian into a soldier.

The 3 steps from civilian to Roman soldier

After the inspection was over and a recruit was deemed suitable for serving in a Roman legion he was appointed to the rank of tiro (= candidate).

The status of Tiro (=candidate) can be seen as an intermediate status between civilian and soldier. Since the recruit had passed inspection and was deemed suitable for serving in a legion he was no longer a civilian. But he still missed 3 formalities, the in numeros referri, the signaculum, and the oath each soldier had to take.

Let`s look at these three formalities separately.

  • In numeros referri

The formality of in numeros referri meant that the name of the recruit was registered in the lists of the legion in which he would serve after getting his basic training.

By the way. The Roman army did not know centralized training facilities in which every recruit would be trained. Rather one cohort of each Legion was tasked with training the recruits who would be distributed over the other cohorts of the Legion when they had finished their basic training.

  • signaculum

The signaculum was a piece of metal that each soldier carried around his neck and that marked the man as a soldier. Because of that piece of metal a soldier was also referred to as signatus (=marked). Additionally the recruit would also get a tattoo or brand on his hand that would function as a more durable mark. More on which bodypart would get tattooed in my article here.

  • The last step to becoming a soldier was the oath each recruit had to swear on the gods and the emperor. Normally that oath was sworn about 4 months after the probatio, the interview during the recruitment process. In situations where soldiers were needed as soon as possible swearing, the oath could also be closer to the probatio.

The oath was usually sworn when the recruit was at his future unit and had absolved basic training.

So there we have the requirements and procedure for recruiting a Roman legionary.

But the Roman army did not only consist of Legions. There was also a similar amount of Auxiliary troops. And additionally, there was also a small number of members of the Praetorian guard.

Let`s look at how the soldiers of these two units were recruited.

The recruitment of the Auxilary troops

The main difference between the Legions and the auxiliary troops, aside from equipment and tasks on the battlefield, was the fact that the Roman legions were made up of Roman citizens while the auxiliary troops were made up of men without the Roman civil right.

That by the way did not only cause differences in the recruitment of the Auxilary units but also in the pay, the retirement, and the length of service that soldiers of the Auxilary troops could expect.

Auxiliary troops were made up of able-bodied men who did not have the Roman civil right. These units were usually recruited from the local, non-Roman population of the Provinces. The names of the units are an indication of where the unit was originally set up and where the first soldiers were recruited. The ala Thracum for example was first set up in Thrace.

By the way, Thrace did not only influence the names of several Auxilary troops, the popular gladiator type Thracian is also connected to that region. More on the Thracian, his equipment, and a video demonstrating his fighting style, in my article here.

In case an Auxiliary unit had a combined name, for example, the ala Gallorum et Pannoniorum, then that unit was created by the remains of two units.

In the case of the ala Gallorum et Pannoniorum that ala was formed by combining the survivors of the ala Gallorum (originally recruited in Gaul) and the survivors of the ala Pannonoirum (originally recruited in the region of Pannonia, a province made up of parts of modern-day Hungary and Austria).

The ala, plural alae, was a cavalry unit made up of 500 to 1.000 men that was included in the Roman Auxilary troops.

Aside from the difference in the legal status the physical requirements for men who wanted to join the Auxilary troops were equal to the physical requirements of joining the Roman legions. Although it seems reasonable that speaking and understanding Latin was probably not a requirement for the non-Roman recruits who wanted to join the Auxilary troops.

By the way, after the soldiers of the Auxilary troops had earned their honorable discharge, more on how long they had to serve here, they earned the full Roman civil right as a retirement gift, more on the retirement from the Roman army in general in my article here.

And while soldiers, both of the Legions and the Auxilary troops were not allowed to marry they would still often have relationships and kids, more on that here. And after retiring a soldier of the Auxilary troops could legitimize his relationship and his children which would also grant them the full Roman civil right.

As a result of that, the legitimized sons of retired soldiers of the Auxiliary troops could join the Roman Legions! Because of that, the Auxilary troops were crucial for the romanization of the provinces! You can find out more about that interesting but unfortunately pretty unknown topic in my article here.

But I digress. Let`s return to the recruitment of Roman soldiers and turn to the last type of unit that is still missing: The Praetorian Guard!

The recruitment of the Praetorian guard

The members of the Praetorian guard enjoyed several advantages over the regular Roman soldier. While both Roman legions and Auxiliary troops were not stationed in Italy the Praetorian guard was. Three of its cohorts were actually stationed in Rome with the rest spread over Italy.

I think you and I both agree that serving your military service in safe and warm Italy is much more pleasant than serving at a border garrison on the rainy left shore of the Rhine with the constant threat of raiding germanic tribes…

Additionally, members of the Praetorian guard served a lot less time than their counterparts in the legions or the auxiliary troops, more on that here, got a higher pay, more on that here, and also received a higher retirement, more on that here.

Because of that, the requirements to join the Praetorian guard were higher than for joining the Roman Legions.

The physical and intellectual requirements and the requirement of a good reputation were shared between the members of the Praetorian guard and normal Legionaries. But until the time of Emperor Tiberius (14-37 AD) men who wanted to join the Praetorian guard had to be born in Latium, Etruria, or Umbria.

The requirement for being born in either Latium, Etruria, or Umbria can be connected to the earliest Roman expansion. By originally only opening the service in the Praetorian guard to men from areas that had been romanized in the early days of Rome the emperors probably hoped that there was not only exclusivity but also a special loyalty connected to that origin.

And a high sense of loyalty was definitely wanted in a unit that was not only tasked with the safety of the Emperor and his family but was also one of the very few units that were stationed in Italy. How important the loyalty of the Praetorian guard was should be demonstrated several times in the course of the Roman Empire. For example when the Praetorian guard assassinated the Emperor and basically sold the Emperorship to the highest bidder.

But that is a story for another time.

If you want to learn more about the daily life of the average Roman soldier I would like to recommend you my article here where I talk about the diet of a Roman soldier and if Roman soldiers were really vegetarians (like it is sometimes claimed).

Take care of yourself because you deserve it. You really do.

Until next time

Yours truly

Luke Reitzer


H.J. Höper: Alltagsleben römischer Legionäre (1985).

M. Junkelmann: Die Legionen des Augustus: Der römische Soldat im archäologischen Experiment (1986).