Making It Happen: The Military of Ancient Rome – Part I

Welcome to Rome Across Europe!

If this is your initial visit with us, thanks for stopping by. If you are back for further adventures with us, then you’re in for a treat.

It’s time to put on your caligae (military boots) and grab your glădĭus (sword) for we are joining the Exercitus Romanus (Roman Army). For those not aware, the growth of Ancient Rome was put onto the backs of its soldiers.

Today we are journeying back to when, and where, it all began as we see how the Military of Ancient Rome made it all happen!

The Backbone of the Roman Empire

According to Caesar Medina, an illustrious historian of Rome over the centuries, the Military of Ancient Rome was a key element in the rise of Rome over 700 years. Growing from a small settlement in Latium on the Mediterranean, Rome became the capital of an Empire governing a wide region around the shores of what the Romans called mare nostrum (our sea).

Livy asserts:

… if any people ought to be allowed to consecrate their origins and refer them to a divine source, so great is the military glory of the Roman People that when they profess that their Father and the Father of their Founder was none other than Mars, the nations of the earth may well submit to this also with as good a grace as they submit to Rome’s dominion.

1st Century Roman portrait bust said to be of Josephus (Ny Carlsberg Glyptotek – Copenhagen, Denmark).

Titus Flavius Josephus, a contemporary historian, sometime high-ranking officer in the Roman Army, and commander of the rebels in the Jewish revolt, describes the Roman people as if they were born already armed. At the time of these historians, Roman society had already evolved an effective military and had used it to defend itself against the Etruscans, the Italics, the Greeks, the Gauls, the maritime empire of Carthage, and the Macedonian kingdoms.

In each war, Rome kept on acquiring more territory. When the Final War of the Roman Republic ended the Res Publica Romana (Roman Republic), nothing was left for the original Emperor, Augustus, to do except declare it an Empire and defend it.

The role and structure of Rome’s Military was then altered during the Empire. It became less Roman, with the duties of border protection and territorial administration being more and more taken by foreign mercenaries with Roman Officers.

SPQR insignia

During the Roman Republic the function of the Military was defined as service to the Senatus Populusque Romanus, an agency designated by SPQR on public inscriptions. Its main body was the Senatus Romanus (Roman Senate), which met in a building still extant in the Forum Romanum (Roman Forum).

Its decrees were handed off to the pair of Chief Officers of the State, the Consules (Consuls). They could levy from the citizens whatever military force they judged was necessary to execute the decree, and often did this by a draft of male citizens assembled by age class.

A modern look at Ancient Roman Officers.

The Officers of the Legion were tasked with selecting men for the ranks. The will of the SPQR was binding on the Consuls and the men, with the death penalty (typically by crucifixion) often assigned for disobedience or failure.

The consular duties were of any type whatever: military defense, police work, public hygiene, assistance in civil disaster, health work, agriculture, and especially construction of public roads, bridges, aqueducts, buildings, and the maintenance of such. The soldiers were kept busy doing whatever service needed to be done: soldiering, manning vessels, carpentry, blacksmithing, clerking, etc.

The men were trained as required but any previous skills, such as a trade, were exploited. They were brought to the task and were protected by the authority of the state.

Location of Roman Legions camps (AD 80).

The Military’s campaign history stretched over 1300 years and saw Roman Armies campaigning as far east as Parthia (modern-day Iran), as far south as Africa (modern-day Tunisia) and Aegyptus (modern-day Egypt), and as far north as Britannia (modern-day England, south Scotland, and Wales). The makeup of the Roman Military changed substantially over its history, from its early history as an unsalaried citizen militia to a later professional force, the Imperial Roman Army.

The equipment used by the military altered greatly in type over time, though there were very few technological improvements in weapons manufacture, in common with the rest of the classical world. For much of its history, the vast majority of Rome’s forces were maintained at or beyond the limits of its territory, in order to either expand Rome’s domain, or protect its existing borders.

Expansions were infrequent, as the Emperors, adopting a strategy of fixed lines of defense, had determined to maintain existing borders. For that purpose they constructed extensive walls and created permanent stations that became cities.

Hadrian’s Wall, a Roman boundary still standing today in Britain.

At its territorial height, the Roman Empire may have contained between 45 million and 120 million people. Historians have estimated that the size of the Roman Army was likely a standing force of 375,000 at the Empire’s territorial peak in the time of the Roman Emperor Hadrian (117 – 138 AD).

This estimate probably included only Legionarii (Legionary) and Auxiliaries (Auxiliary) troops of the Exercitus Romanus. In the late Imperial period, when vast numbers of Foederati were employed by the Romans, it’s been estimated the combined number of men in arms from the Western Roman Empire and Eastern Roman Empire numbered closer to 700,000 in total (not all members of a standing army), drawing on data from the Notitia Dignitatum.

Relief scene of Roman Legionaries marching, from the Column of Marcus Aurelius (Rome, Italy, 2nd Century AD).

Initially, Rome’s Military consisted of an annual citizen charge of performing military service as part of their duty to the State. During this period, the Roman Army would prosecute seasonal campaigns against largely local adversaries.

As the extent of the territories falling under Roman suzerainty expanded, and the size of the city’s forces increased, the soldiery of Ancient Rome became increasingly professional and salaried. As a consequence, military service at the lower (non-staff) levels became progressively longer-term.

Roman military units of the period were largely homogeneous and highly regulated. The Army consisted of units of Citizen Infantry known as Legions (Legiones) as well as non-legionary allied troops known as Auxilia to provide light infantry or cavalry support.

Roman Soldiers on the cast of Trajan’s Column (Victoria and Albert museum, London).

Military service in the later Empire continued to be salaried yearly and professionally for Rome’s regular troops. However, the trend of employing allied or mercenary troops was expanded such that these troops came to represent a substantial proportion of Rome’s forces.

At the same time, the uniformity of structure found in Rome’s earlier military forces disappeared. Soldiery of the era ranged from lightly armed mounted archers to heavy infantry, in regiments of varying size and quality, with an increasing predominance of cavalry rather than infantry troops in the late Empire.

In the Legions of the Republic, discipline was fierce and training was harsh. All of this was  intended to instill a group cohesion or (esprit de corps) that could bind the men together into effective fighting units.

The testudo formation in a Roman military reenactment.

Unlike opponents such as the Gauls, who were fierce individual warriors, Roman military training concentrated on instilling teamwork and maintaining a level head over individual bravery. Troops were to maintain exact formations in battle and skillfully use the sheltering of one’s shield, thus being able to deliver efficient stabs when an opponent made himself vulnerable (the testudo).

A modern reconstruction of an Aquila.

Loyalty was to the Roman State but pride was based in the Soldier’s Unit, to which was attached a military standard (most likely the Aquila or Eagle). Successful units, such as the 20th Legion which became the XX Valeria Victrix (Valiant and Victorious 20th), were awarded with accolades that became part of their official name.

Of the martial culture of less valued units such as sailors, and light infantry, less is known. It is doubtful that other training was as intense or its esprit de corps as strong as in the Legions.

Although early in its history troops were expected to provide much of their own equipment, eventually the Roman Military was almost entirely funded by the State. Since soldiers of the early Republican Armies were also unpaid citizens, the financial burden of the Army on the State was minimal.

However, since the Roman State did not provide services such as housing, health, education, social security and public transport that are part and parcel of modern states, the Military always represented by far the greatest expenditure of the State.

During the time of expansion in the Republic and early Empire, Roman Armies had acted as a source of revenue for the Roman State, plundering conquered territories, displaying the massive wealth in triumphus (triumphs) upon their return, and fueling the economy to the extent that historians believed the Roman economy was essentially a plunder economy.

Roman coins grew gradually more debased due to the demands placed on the treasury of the Roman State by the Military.

However, after the Empire had stopped expanding in the 2nd Century AD, this source of revenue dried up. By the end of the 3rd Century AD, Rome had ceased to vanquish.

As tax revenue was plagued by corruption and hyperinflation during the Crisis of the Third Century, military expenditures began to like the weight of the world upon the shoulders of Atlas on the finances of the Roman state. It now highlighted weaknesses that earlier expansion had disguised.

Several additional factors bloated the military expenditure of the Roman Empire. First, substantial rewards were paid to barbarian chieftains for their good conduct in the form of negotiated subsidies and for the provision of allied troops.

3rd Century Roman Cavalry

Secondly, the military boosted its numbers, possibly by 1/3 in a single century. Third, the military increasingly relied on a higher ratio of Equites Romani (Cavalry) units in the late Empire, which was much more expensive to maintain than Infantry units.

As military size and costs increased, new taxes were introduced or existing tax laws reformed in the late Empire to finance it. Even though there were more inhabitants available within the borders of the late Empire, reducing the per capita costs for an increased standing army was impractical.

A large number of the population could not be taxed because they were slaves or held Roman citizenship, both of which exempted them from taxation. Of the remaining people within the Empire, a large number were already impoverished by centuries of warfare and weakened by chronic malnutrition.

Still, they had to handle an increasing tax rate and so they often abandoned their lands to survive in a city. By 440 AD, Roman Law conditions that the State had insufficient tax revenue to fund an Army of a size required by the demands placed upon it.

Ancient Rome’s marching camps were a crucial part of every Roman offensive.

The military capability of Rome, its preparedness or readiness, was always primarily based upon the maintenance of an active fighting force acting either at or beyond its military frontiers. Because of these deployments, the Roman Military kept a central strategic reserve after the Social War.

We hope you enjoyed today’s adventure. We look forward to having you join us again as we conclude Rome’s military might with Part II.

Till next time, Don’t Stop Rome-ing!



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