The ancient Roman military is renowned for its professionalism and power, with legions spreading all the way from Britain to Iraq. But what percentage of Romans were soldiers?
The number of soldiers in the Roman army and the population of the Roman Kingdom, Republic, and Empire varied, making it hard to say what percentage of Romans were soldiers. In the 2nd century AD, around 0.8% of the population seems to have been in the military, but records may not be reliable.
To find out more about the size of the Roman army throughout history, read on.
Start of the Roman Army
While it is difficult to determine what percentage exactly of the Roman population were soldiers, we can get an idea of the size of the Roman military throughout history along with the size of the Roman population to then determine what a rough percentage could have been.
Many sources regarding the size of the Roman army seem to have been written after the fact and may have exaggerated for propaganda purposes, so these figures should all be considered with a little suspicion.
According to Plutarch, Romulus established the first Roman legion in the 8th century BC with 3,000 soldiers and 300 cavalry units. According to Livy, this eventually expanded to 17,000 soldiers and 1,800 cavalry units in the 6th century BC under King Servius Tullius.
The Roman Republic was established in 509 BC and, following a series of internal conflicts, early expansionist campaigns against the Etruscans, and invasions by outsiders like the Gauls, it started to expand more during the Latin War of 340-338 BC.
According to Livy, although he was writing around 300 years after the fact, there were around 20,000 Roman soldiers and 1,200 Roman cavalry, as well as around 20,000 allied forces and 3,600 allied cavalry called socii.
The Roman soldiers were divided into two armies featuring two legions each, with around 4,200 to 5,000 soldiers and around 300 cavalry units in each legion. This configuration of a Roman legion would continue throughout the age of the Roman Republic.
Growth of the Roman Army
During the First Punic War (264-241 BC), there were six Roman legions with a total of around 30,000 soldiers, while there were many more allied soldiers along with the introduction of a Roman navy. In the Second Punic War (218-201 BC), there were 23 legions made up of Roman and allied soldiers, with around 115,000 soldiers and 13,000 cavalry units, as well as a navy of around 150 ships.
By the end of the last war of the Roman Republic, with Octavian’s victory leading to the establishment of the Roman Empire in 27 BC, there were about 60 Roman legions at an upper capacity of around 318,000 troops. However, few of these legions would have been at full capacity.
This number continued to expand throughout the Roman Empire and during Trajan’s reign (98-117 AD), there were about 380,000 soldiers, with 30 legions, and around 165,000 Roman legionaries, and 380 auxiliaries (with around 200,000 to 220,000 auxiliary soldiers). By the time of Septimius Severus (193-211), there were around 500,000 soldiers with 33 legions and 400 auxiliary units.
The size of the army is believed to have reached its peak during the time of Constantine I (306-337) with around 65 legions and a total of around 645,000 soldiers including legionaries, auxiliary units, the Praetorian guard, and the navy.
However, there is considerable debate over the size of the army and how standardized legions were. Indeed, the Roman army may have been far smaller or far larger than these figures, making it difficult to determine the percentage of the population in the army.
The Population of Ancient Rome
As the Roman Empire grew in size, so did its population and army, meaning it is difficult to determine the percentage in the military. Estimates for the population of the Roman Empire vary, with some as low as 39 million during the 4th century and others suggesting around 70 million or even as much as 100 million.
The Roman Empire had a high fertility rate, but high infant mortality too, and half of all Romans died before the age of 10. Most of those who lived beyond the age of 10 died by 50, but it is thought to have reached its peak in the 160s of around 60 to 70 million people, while a million people lived in Rome itself.
Therefore, if we use a figure of 65 million people as an estimated population and put the size of the Roman army at around 500,000 soldiers, then approximately 0.8% of the population would have been soldiers.