The Roman Army After Marius' Reforms

An Introduction

Author: T Wake, 28 Feb 06

Page 1

Any outline of Roman history covers, at one stage or another, the Roman Army. This is with good reason. For its entire history, Rome has relied on the military machine for defence and expansion. In the earliest days, when Rome was a fledgeling city state, its soldiers provided protection (notably failing in 387 B.C. when the Celtic Gauls defeated the Roman Army at the river Allia and proceded to sack Rome itself) and throughout the time of republic and empire control of the legions became fundamental to power in Rome.

This article will give a very brief overview of the Roman army as most people think of it - post Marius' reforms. Future articles will study the Roman military machine in greater depth.


Prior to the Celtic invasion, and from about 500 B.C. the Roman army consisted of around 6000 soldiers. These were made up from a levy (Latin. Legio) of all eligible Roman citizens between the ages of 17 and 46. The prime eligibility criteria was simply land ownership at this time. These soldiers were heavy spearmen, almost identical to the Greek Hoplites from the "classical era." In the earliest days of the republic (c. 509 B.C.) Romans organised these legios into straight forward "armies" of around 500 - 1000 men with very little similarity between them.

First reform - Early Republic

Following the disaster at the hands of the Celts, and certainly by c. 320 B.C. the Roman republic had drastically re-organised it's armies into something resembling what we, today, think of as "legions." According to contemporary writers (notably Polybius and Livy - although they often differ), the Republican legions was made up of five basic troops:

Each legion had around 300 cavalry. Made up from the richest citizens who could afford the horses.
Light Infantry - Velites
Mainly poor soldiers who couldn't afford to equip themselves properly. Used as scouts and skirmishers.
Heavy Infantry - Hastati
The first line of the battle. These were the youngest soldiers and armed with javelins (pilum) and short swords (gladius).
Heavy Infantry - Principes
The second line of the army. These are men in the prime with considerable battle experience. Armed the same as the younger hastati, the principes were expected to "steady the line."
Heavy Infantry - Triarii
The third line was made up of the veterans. Often soldiers who were close to the end of their service, the triarii provided the "backbone" of the legion. They were armed the same as the front two ranks but appear to have had longer spears.

All three lines of heavy infantry were organised into ten "maniples." This grouping of ten maniples was the smallest fighting unit of the Roman army, and comprised two "centuries." In the case of the hastati and principes, maniples consisted of about 120 - 160 men. The triarii made up ten maniples of about 60 men. Additionally, each maniple had a unit of about 40 velites (light infantry) attached to provide flanking attacks. The Roman cavalry was normally used as a screen or long distance scouts and, whilst socially prestigious, were rarely significant in battles.

When it came to battles, the Romans formed their legions into a formation called the "triplex acies" (Triple Battle Order) which looked a bit like a chequerboard. In this formation, the principes covered the gaps in the hastati line, and the triarii covered the gaps in the principes line (see figure 1). This formation could often present a front to the enemy over a mile long. As well as the Roman citizens in the legion, the army was supplemented by an similar number of allies (around 4-5000 infantry, 900 cavalry), commanded by Roman officers. These auxillaries were normally positioned on the flanks of the army and were known as alae (wings).

triplex acies - triple battle order formationFig 1: triplex acies formation

Success and Failure

For nearly two hundred years, the Roman army and the triplex acies were nearly invincible. The formation allowed the Romans to repeatedly beat technically and numerically superior forces such as the Macedonians. In addition, the flexibility offered by the combination of formation and Roman discipline, enabled the Romans to defeat attacking elephant and cavalry forces (the maniples would open to let the charge pass, then close and destroy them) which ensured Roman dominance over the classical world.

Until nearly the end of the second century B.C. the Romans were by far the dominant military force. Their main weakness was the lack of professionalism - after each campaign the army was disbanded and had to be recruited anew for the next one. This lead to some spectacular defeats, for example the armies that fought Hannibal of Carthage were notably inexperienced and embarassingly defeated. When a general had the chance to keep his legions formed for long periods of time, they were superb on the battle field (for example, under Scipio the Roman army had a run of victories 202 - 168 B.C.)

Eventually though, the disband and reform approach became unsustainable. The closing years of the second century B.C. were plagued with military defeats and the reputation of the Roman army was badly damaged. This culminated in the battle of Arausio in 105 B.C., where the Cimbri and Teutones (proto-Germanic tribes) destroyed over 80,000 Roman soldiers.

Following this devastating military defeat, a popular Roman general named Marius realised the Roman army needed a major overhaul. What came next went down in history as "Marius' Reforms" and helped the Roman army maintain another 500 years of military might.

Marius' Reforms

General Gaius Marius

Gaius Marius lived 157 - 86 B.C. and was the uncle to Gaius Julius Caesar. Marius was a "new man" in Roman parlance, which meant that although he was from an equestrian family (Roman upper classes) he had no ancestors of senatorial rank. Born sometime around 157 B.C. in Arpinum, a town in southern Latium, Marius came from a family that was locally important (as befitting his equestrian status) and had established relationships with more socially important Roman families in Rome itself.

Marius' military career began early, although some accounts relate that Marius' military service was only viewed as a step ladder to greater things. During his time with Rome's legions, Marius came to notice at the battle of Numantia, where he served under the famous Scipio Aemilianus (grandson of Scipio Africanus).

Taking advantage of his family connections with powerful Romans, and his fame from service in Africa, Marius rose to power following the murder of Gaius Gracchus in 122 B.C. and one of his first acts as tribune was to pass a law preventing the inspection of ballot boxes to prevent intimidation of voters.

After election to Consul in 107 B.C., Marius presented himself as an honest, down to Earth soldier of Rome, who was (unfortunately) surrounded by corrupt, inept, patricians who were mis-managing the country and the army. Marius defeated the senate's attempt to confirm Quintus Caecilius Metellus Numidicus (Metellus) as governor of Africa (using a cunning procedural ploy) and, through a special election gained the position as Roman commander in chief for Africa.

As the commander of the Roman forces in Africa, Marius was deeply involved in the war against the Numidian King, Jugurtha, and from this conflict his reforms began.

The Reforms


One of the first things Marius achieved was the abolition of the property qualifications for service in the legions. Since the earliest days the Roman army had been recruited from landowners who could afford to buy their own equipment. Even under the Gracchan agrarian reforms people who didn't own enough property for the fifth census class were exempt from military service. While this functioned well for most of the empire, by the late second century B.C. it was failing to provide anywhere near enough soldiers for Rome's needs. The change of the property limits for the fifth census class from 11,000 sesterces down to a trifling 3000 still failed to provide enough fighting men and by 109 B.C. the consuls had requested suspension of Grachus' levy restrictions.

Realising he needed lots of soldiers to successfully pursue a war in Africa, Marius completely ignored the census qualifications for military service and recruited his soldiers with no regard to land ownership. Marius recruited extensively from the capite censi (also known as the "head count" - mostly illiterate, landless peasants)

This change to recruitment had a very significant effect on the make up of the Roman legions. From this point onwards, Rome's legions would be made up of the very poorest members of society - of which Rome had lots at this point in time! For years, the Roman small holders had been moved out of their farmsteads by wealthy Roman senators and patricians who then put slaves to work on the land. Following the Gracchan reforms, the population of Rome itself had increased dramatically, often ex-soldiers, and all these people were now poor and landless. Marius' recruitment change offered them a future.

As the Roman army was now made up of landless soldiers, they became dependant on their General to provide them with land and money. This was a signifcant change, although it appears to have been unintentional and something Marius himself never took advantage of. In previous years, the legions owed their prime loyalty to the Senate and Rome itself. Following from Marius' change to the recruitment, legionaries were now only really loyal to their Generals. Additionally, unlikle previous generations where the soldiers had a home and land to go back to between wars, Marius' army was now one of "professional" soldiers. These were now men who would serve their General for 20 - 25 years before retiring. If their General was successful the soldier could look forward to a grant of land - again re-inforcing the bond between the General and his soldiers.

While it appears Marius was unaware of the social change he wrought, it was not completely unnoticed. In less than twenty years, Marius' ex-quaestor (elected official) Sulla would use the loyalty of his Legions to march on Rome. Sulla broke from tradition and crossed the pomerium (City Limits) despite the outrage this caused.

The Legionnaires and Their Equipment

After abolishing the property qualifications, Marius did away with all the distinctions based on social class. Marius removed the velites and the cavalry from the Roman army completely (their roles going to the allied troops and native soldiers). All legionaries were identically armed with a pilum and gladius and the age based lines were abolished.

The Roman army had always been infantry heavy, and now under Marius it was doubly so. He decreed that all the soldiers would carry their tents, weapons and food themselves - earning the Legions the nickname "Marius' Mules." The humour aside this was an excellent change, as it created the responsive, capable soldiers people today associate with the Roman Legions.

An addition, often overlooked, change that Marius instigated was the redesign of the pilum. Marius had it altered to so that the sharp head was attached to the shaft by a thinner joint (creating the typical image we have for the pilum today). This ensured that when the legionaries threw the pilum, the head would break off on impact and their enemies would be unable to pick it up and throw it back.

The Structure of the Roman Army

Another of the critical changes was the reorganisation of the Army as a whole. Marius did away with the maniple as the basic unit (although administratively they remained for a short time) and made the cohort the main tactical sub-unit. Each legion now comprised ten cohorts.

Cohorts were made up of about 480 legionaries, divided into six centuries of about 80 men (only in the very earliest days of the Roman Legions was a century actually 100 men...), led by a Centurion. In future years, the prima cohors ("First Cohort") would be increased to double strength (approximately 800 men) and be the "elite" of the legion.

The alae were no longer the "allies" covering the Roman wings, but cavalry specialists recruited from the auxiliaries. Organised into units of either 512 or 768 men these provided a strong, fast screen to defend the legions.

To encourage loyalty to the legion and provide a rallying point, Marius also introduced the silver aquila ("eagle") as the main standard. This symbolised the pride and identity of the legion and developed myths of its own.

The final, significant, change introduced by Marius was the concept of promoting soldiers from within the ranks. Again, born out of expedience (the advantage of having skilled, capable soldiers leading the centuries as opposed to political appointees was significant for the Roman army) this change had additional consequences. The newly promoted soldiers were likely to be even more loyal to their General and resistant to commands from the quaestors and other (appointed) officers. Likewise, the soldiers themselves were likely to show more loyalty to "one of their own."


Following on from his experiences in the Roman Army, Marius introduced some wide ranging reforms which drastically altered the Legions. While there is no reason to believe any political or social motive for the changes - most of the evidence points to Marius making these changes simply to increase the combat effectiveness of the legions - there is no doubting the long term effect his reforms had.

Marius created, for the first time, a professional army made up from landless citizens. These soldiers were capable, and willing, to fight all year round and had little ties to "home." A significant result of this meant that the soldier, owing no allegiance to Rome, was often more loyal to his General than the country he defended.

From a purely military point of view, the reforms helped change the already efficient Roman army into what could best be described as a killing machine which had no equal for nearly 500 years. After the set backs of Arausio this was welcomed by the Roman people and Marius was repeatedly elected consul. Even in his late sixties Marius was able to lead the Roman army during the Social Wars of 91 - 88 B.C.

It would probably not have been possible for Marius to predict the far-reaching consequences of his reforms, but his "New Model Army" would provide the basis for Julius Caesar crossing the Rubicon in 49 B.C. and for the later Praetorian Guards. Unfortunately for the Romans, one of the longest term shifts this military change caused was the power the Praetorians could wield when it came to finding new emperors. Even from the time of Marius it became quickly apparent that the way to power in Rome now lay in controlling the legions.

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This document came from


Sources Used

Haywood, J., "The Romans," Andromeda, Oxford, 1994

Marks, A., & Tingay, G., "Romans," Usborne, London, 2003

Cite this work

Wake, T., "The Roman Army After Marius' Reforms," http:// / roman_army_print, 28 February 2006.

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