The Roman Army: Its Evolution and Growth

From the lecture series: The Roman Empire: From Augustus to the Fall of Rome

By Gregory S. Aldrete, Ph.D., University of Wisconsin Green Bay

The Roman army was one way by which people from different provinces came to Rome and made it their home. The Roman army was also a path to social mobility. Many young men from all over the Roman Empire left provincial towns and villages to see the world and make a life.

Roman soldiers on the cast of Trajan's Column
Roman soldiers came from all parts of the Empire, for various reasons. (Image: Gaius Cornelius assumed (based on copyright claims). / Public domain)

Apion’s Adventure to Rome

A teenager by the name of Apion started on the adventure of his life sometime during the 2nd century AD. He had made a decision to leave his sleepy hometown in Egypt and join the Roman army. So he traveled to the port of Alexandria and set off for Rome in a ship. On the way, however, the ship was caught in a storm.

Terror-stricken by the storm, Apion prayed to the god Serapis for salvation. Serapis answered his prayers and the ship survived. It ultimately docked at Misenum, the naval station of Rome at the bay of Naples. He got himself in the military, though it is not clear whether it was the Roman army or navy. He was immediately rewarded with an enlistment bonus of three gold coins which would also pay for his traveling expenses. He also got a new Latin name, Antonius Maximus — ‘Big Tony’ — indicating he was a tough lad. 

All this is known to us because Apios wrote a letter to his family in Egypt soon after his arrival in Rome, narrating his adventures. It starts like this: “Apion to my father Epimachus. Very many greetings. Above all, I pray for your good health and you may always be strong and fortunate, along with my sister, her daughter, and my brother… Everything is going fine for me.” After describing the storm in the sea and the drama that followed, he tells them about his golden reward. He finishes the letter by saying, “Write me a letter about the welfare of my sister and brother… I have sent you through Euctemon a portrait of myself. My new Roman name is Antonius Maximus.”

This is a transcript from the video series The Roman Empire: From Augustus to the Fall of Rome. Watch it now, on The Great Courses Plus.

Life In The Roman Army

It seems Antonius prospered in his new life because there is a second letter from him that looks like having been written considerably later. It goes like this, “Antonius Maximus to Sabina, his sister, very many greetings. Before all else, I pray that you are well, for myself I am well. .. My wife Aufidia greets you and so does my son Maximus, whose birthday is the thirtieth of Epeiph according to the Greek calendar, as well as my daughters Elpis and Fortunata.” 

These two letters give a peek into the life of just one family living in the Roman empire, but such experiences would have been common among the recruits. The Roman army is known to be the most successful military in history due to which the Romans were first able to win over a vast empire and then maintain it.

The letters from Apion put a human face on the Roman war machine. We all can easily identify with Apion’s excitement and nervousness at leaving his home for the first time, his honor in his achievements, and his yearning for news about his family from whom perhaps he was separated permanently.

Another point made by these letters is that the Roman army not only won the Mediterranean, but it was also was a mechanism by which thousands of people like Apion from different provinces came to Rome and made it their home, learned their culture and customs, and perhaps learned to speak Latin too. The Roman army was also a path to social mobility due to which many such young men were able to gain status and add to their wealth. There are so many examples of the sons joining the military following their fathers and even climbing to higher ranks than them. Maybe Maximus junior also followed this path. 

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Changes In The Roman Army

This is apicture of emperor Komnenos.
Emperor John II Komnenos, the most successful commander of the Komnenian army. (Image: Hagia Sophia / Public domain)

Over 1500 years, the Roman army underwent many changes. In the initial stages of Roman history, and throughout much of the Republic era, the army was more like a seasonal citizens’ militia which mostly comprised of farmers. With the growth of Rome in the Middle Republic, and as wars became longer and more demanding, the Roman army started evolving, adopting new tactics and weapons. This style of the military is sometimes called the Polybian system, named after the ancient author who gave its full description.

The Roman army had become more professionalized by the late Republic, emphasizing greatly on discipline. And by then, soldiering had moved from being a part-time occupation to a full-time career. Renowned people like Marius and Julius Caesar brought about more reforms. Augustus made widespread changes in the Roman military after winning the civil wars and establishing the Principate. This style of military is the one that existed in the many early centuries AD during the peak of the Roman empire.

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How Big Was the Army?

A Roman infantryman.
The Roman army accounted for over half the non-farming population of the Roman empire. (Image: Antoine Glédel / Public domain)

But how big was the Roman army? During the reign of Augustus, the number of legions was 28 and that number kept gradually rising with subsequent emperors. It became 30 during the 2nd century AD and 33 during the 3rd Century AD. Since each legion had a strength of 5500 on paper, the number of legionaries during that period could be anywhere between 150,000 to 200,000.

These legions comprising of citizens were supplemented by auxilia. These were military units that were raised from the non-citizen residents of the empire. It seems that the number of such auxiliaries in the Roman army was equal to or greater than the legions; meaning another 200,000 to 300,000 soldiers.

And lastly, there were many military and paramilitary units like the Roman navy and the Praetorian guard. The collective strength of these units was around 50,000 men. So the total strength of the Roman army during the many first centuries AD was very close to half a million. This was a huge number to maintain as permanent standing force for a society that existed prior to industrialization and was majorly dependent on agriculture, because it meant more than half of the non-farming population of the empire was in the army.

Therefore, much of the economic surplus produced by the vast Roman empire went into feeding, equipping, and paying this military force.

Common Questions About the Roman Army

Q: What did the Roman army comprise?

The Roman army comprised many groups of soldiers and each group was known as a legion. A legion had over 5000 soldiers. Every legion had its individual name, badge, number, and fortress.

Q: Was the Roman army really good?

The Roman army was the biggest and the most unkind force of the ancient world. Its strength was one of the main reasons that Rome became so powerful. The soldiers had the best of training, weapons, and armors and it was advanced beyond its time.

Q: How much was the pay of the soldiers of the Roman army?

The soldiers of the Roman army were paid 225 denarii per year from the time of Marius. Later Domitian raised their pay to 300 denarii.

Q: What were Roman soldiers given on retirement?

On retirement, a Roman legionary was given a piece of land or an equal amount of money. He then usually became a prominent member of society.

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