How did Marius Reform the Roman Army?

The Marian reforms were established in 107 BC by the politician Gaius Marius. They were the reformed ancient Roman Army named after Marius.

The changes arose after the Roman Republic’s military and logistics stopped flowing around the end of the 2nd Century BC.

The Roman army’s personnel and physical resources were strained due to the growing invasions around the Roman territory and the years of military combat around the Mediterranean.

Gaius Marius was a Roman commander and politician who lived from 157 BC until 13 January 86 BC.

He held the post of consul an unprecedented seven times throughout his tenure, having won the Cimbric and Jugurthine wars. 

He was well known for his significant improvements to the Roman forces. He established the precedent for the transition from the middle Republic’s militia levies to the late Republic’s professional soldiery. 

He also improved the pilum, a javelin, and made large-scale reforms to the Roman army’s logistics system.

Marius, born into a prosperous provincial Italian family in Arpinum, had his first combat experience while serving with Scipio Aemilianus during the Siege of Numantia in 134 BC. 

In 119 BC, he was elected tribune of the plebs and enacted legislation to minimize the aristocratic influence in elections. After being elected praetor in 115 BC, he became governor of Further Spain for the first time. 

While there, he battled against outlaws. He married Julia, Julius Caesar’s aunt when he returned from Spain.

Marius suggested dramatic changes to create a professional and energetic Roman army who would be ready to stay with him permanently.

The reforms transformed the Roman military machine by creating proper legionary and cohort units. 

Due to the changes, the general is also responsible for equipping and handling the Roman Army. At the same time, the Roman troops were awarded Roman citizenship and a portion of land by Marius. 

Consequently, these changes substantially influenced Rome’s military superiority and contributed to the Late Republic’s socio-political turmoil.

These developments stayed primarily intact until the Roman Empire’s demise, although there were alterations in specific structures and administration sectors. These alterations were initiated by Augustus and subsequently by Diocletian.

What did Marius achieve?

Gaius Marius was one of the Roman Republic’s most prominent leaders. He was elected consul seven times in a row.

He also made significant modifications to the Roman army, altering Rome’s destiny and transforming it into the world’s most powerful civilization.

How did Marius deal with the Roman army’s personnel shortage?

Due to a lack of personnel, Marius broke with tradition by recruiting volunteers from outside the propertied classes, which had hitherto been the only ones liable for duty.

How did Marius die?

Marius received his prophesied seventh consulship, which was more than any Roman had ever had, but his time was cut short.

After just a few days, his mind and body started to deteriorate, and by mid-January 86 BCE, he died, supposedly of pleurisy, at the age of 70.

The Pre-Marius Roman Army

Level of the army, detail of the carved relief on the Altar of Domitius Ahenobarbus
Level of the army, detail of the carved relief on the Altar of Domitius Ahenobarbus

The pre-Marius Roman army was similar to the Greek Poleis consisting of only the male population. The army to be included would be selected through the process known as Dilectus, where the sitting consuls chose the army a lot.

It was the obligation of all the men to serve the army unless they were physically incapable.

Drafted soldiers were organized into four legions, each formed yearly; they were subjected to intense training before starting a war. 

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While on the campaign, the soldiery earned experience, but they were dissolved once the campaign season or the war was over.

Garrison forces were discharged at the commander’s discretion in a similar manner done in Macedonia and Hispania.

Soldiers were poorly paid, if at all, and salary delays were infamously prevalent. As a result, the main form of remuneration was pillage and plundering shares.

Even the ordinary soldier had to meet severe property and census conditions to join the troop of pre-Marian Roman:

He must be in the sixth census class or above (the adsidui, or “tax-payers”). He was required to possess property worth 3,500 sesterces. And finally, he had to provide his weapons.

These restrictions evolved. Only those with total assets of 10,000 asses or more were eligible to be a part of the military serving during the Second Punic War.

This method of citizen-soldiers bringing their equipment of at least equivalent caliber worked effectively as long as the conflicts were brief and fought in the area near their home.

With the rapid development of the Roman territory, wars grew more lengthy and lasted for many years. 

Farmers leaving their homes to battle sometimes faced a disaster due to such exceptionally extended duty lengths.

The selected troops functioned within the maniple system that evolved in the 320s BC as an alternative to the standard ‘Italic’ phalanx. They were divided into various lines based on their wealth, war experiences, and age.

The Velites

A veles in combat
A veles in combat

The troop of Velites included the 5th class proletarii, mostly the youngest citizens. They could not even afford to purchase a shield, helmet, armor, or even a gladius. 

They were placed on the front line but were unarmored. They would throw javelins and fire missiles to confuse the enemy, during which the hastati would move forward with their attack. 

The Hastati 

Hastati roman army full set
Hastati roman army complete set

They were fourth-class people who could afford rudimentary armor, a shield, and a gladius.

The hastati, the pre-Marian legion, belonging to the 1st rank of heavy, maintained the front line. This troop consisted mainly of aggressive youths that belonged to the middle and lower-middle class. 

The armor and front-line position invariably resulted in the heaviest deaths in each fight. 

Those showing efficient performance during the battle earned advancement to the higher positions – as the principles and stepped upwards towards social mobility.

The Principes 

Roman legionary from the principes
Roman legionary from the principes

Principes were third-class people who could purchase a complete suite of the armor of quality, a giant shield, and a bronze helmet in conjunction with their swords.

These pre-Marian forces nearly resembled the conventional legionnaire ultimately created by the Marian reforms. They were considered the heart of the pre-Marian legion.

They positioned themselves just after the hastati and substituted them in the front row if they could not breach the opposing formation on their own, which was usual. 

Allowing the opponent to exhaust themselves on the hastati before confronting the principes was generally practical.

The Triarii 

Triarius metal armor at the Flavian Amphitheater, Rome
Triarius metal armor at the Flavian Amphitheater, Rome

The triarii, or the last unit of the infantry, was limited to seasoned principes veterans and anchored the whole line of the Roman battle.

They belonged to the elite section of the pre-Marian legion, fighting in the manner of hoplites in the rear of the formation. 

They were hardly used throughout the battle as they were only utilized when the hastati and principes became unable to breach the enemy’s line and left for the retreat.

The phrase ad triarios redisse (“to fall back on the triarii”) was employed to describe a last, valiant effort to save a terrible situation.

The Equites 

Equites, agile cavalry
Equites, agile cavalry

Equites were agile cavalry who wielded a one-handed light spear. They were affluent individuals of the equestrian class who could purchase a horse. 

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They often moved around the infantry line’s flanks, breaking up opposing skirmisher and missile groups and pursuing troops the infantry had defeated.

They were also the principal scouting element for the legion. 

Marius as a Consul in the Roman Army

Bust of Marius instigator of the Marian reforms
Bust of Marius, instigator of the Marian reforms

Once the patricians had formed an army, one of them would usually lead it into combat. Not all appointed consuls were capable of commanding an army.

For instance, one of the consuls, Gnaeus Papirius Carbo, in 113 BC, was beaten at the Battle of Noreia by raiding Cimbri and Teutonic tribes. 

Following that was a lengthy battle in Africa versus King Jugurtha of Numidia. Quintus Caecilius Metellus Numidicus was dispatched to gain victory over Jugurtha. However, there was no victory even after battling for 2 years.

In 108 BC, Gaius Marius, one of his trusted legates, suggested Metellus remove him from his responsibilities so that he may rejoin Rome to become the consul.

Marius had no army when he became junior consul in 107 BC and was tasked with bringing the conflict with Jugurtha to a close.

The armies led by Metellus in Africa were sent to Lucius Cassius Longinus, the senior consul, to drive the Cimbri.

They were invading the Roman province of Transalpine Gaul once again (Gallia Transalpina). 

Marius had no men to fight the war in Africa because the eligible populace from where he might raise an army had been badly reduced by previous disasters and the latifundia’s growth at the cost of landowners. 

It was evident that a transitory army based primarily on rigid qualifying rules resulted in a restricted quantity of recruits and military shortages that lasted for a short period. For this, he had to implement a variety of measures and reforms.

The Marian Reforms 

Relief scene of Roman legionaries marching, from the Column of Marcus Aurelius, Rome
Relief scene of Roman legionaries marching from the Column of Marcus Aurelius, Rome

The essential Marian reform consisted of incorporating the landless masses of Rome, the capite censi, and men without property to be evaluated in the census.

The male population belonged to the category where they could quickly be recruited despite lacking many properties. 

Marius planned for the state to distribute arms to the impoverished people since they could not buy their weapons and armor.

As a result, he gave the disaffected masses permanent work to pay the working troops and the potential to acquire war spoils. 

With few other options for achieving prestige, the people rushed to join the new army of Marius.

Furthermore, professional soldiers were recruited for a 16-year enlistment period, which was eventually increased to 20 years’ whole duty and five years as evocati under Augustus’ reforms. 

The availability of the recruits was boosted by keeping them away from the restrictions related to property and giving them equipment of high quality.

As a result, impoverished Roman citizens were permitted to serve in the Roman military.

Each soldier was made to furnish their equipment under the previous system. Still, the new massive number of impoverished troops owing to the other Marian reforms could not continue.

Marius modified the system by delegating responsibility for army provisioning to the general. 

Roman troops had to carry their supplies, weapons, and meals for many days. The century brought all the weapons and accessories needed to feed and sustain it. As a result, they were dubbed “Marius mules.” 

These logistics shifts significantly decreased the size of the baggage train necessary for support, allowing the army to be considerably more flexible.

This was likely a practice that existed before the Marian reforms and was merely reinstated, implying that the Marian reforms just restored this tradition.

Marius’s second major reform was the establishment of a permanent army. Marius was skeptical of the army’s volunteer organization, which dissolved after a short duty.

Alternatively, he established career troops with fixed jobs that were free to access the available equipment and underwent training. This process went on throughout the year, even when there was no war.

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Thanks to the increasingly standardized equipment, the uniformed and rigorously schooled legionary were the cornerstone of the Roman force.

Marius then reformed the Roman legion out of a maniple system and turned into cohorts with about 4800 troops.

A legion’s internal structure consisted of ten cohorts of six centuries each. The century was headed by a centurion and comprised 80 troops. 

Each century was split into ten contubernia, each commanded by a decanus. There were eight legionaries in the contubernium. The century fought as a group, marched as a group, and camped as a group.

An army comprised of two to six legions organized together. Constant training maintained the legions in peak physical form and discipline, making them among the greatest in the ancient world.

The cohorts were deployed in a condensed line to promote discipline than the preceding maniple line.

Marius managed to pass legislation that provided savings facilities in the guise of land rights as the third reform.

Members of the number of attendees who had finished their term of duty would be awarded a pension. 

They would also be awarded a piece of land in the captured province to settle on by their general. Officers and commanders received monetary prizes 10 to 25 times a regular foot soldier.

Marius offered the people of the Italian allies the Roman nationality under a condition. The Italians were to fight for Rome and serve the Roman force for a certain period.

Marian Reforms’ Impact on the Roman Republic

Ahenobarbus relief
Ahenobarbus relief

The earliest and most evident impact was an increase in the army’s military capabilities.

When war loomed the Republic, a general no longer had to rush to assemble troops from the citizen, prepare them to battle, follow military instructions and discipline, and then head towards combat fully prepared.

This was critical to the expansion and effectiveness of the Roman military. It led to the Romans’ ongoing victory on the battlefield.

Furthermore, establishing a competent standing army was better adapted to governing the expanding empire

It boosted the speed with which Rome could deploy forces. Generals in the Marian legion had to deal with fewer leaders, allowing them to deliver more sophisticated instructions to the army.

Another advantage of this transformation was the relocation of legionaries who had retired to conquered territory.

This aided in the region’s integration into a Roman province and “Romanization,” lessening dissatisfaction and resistance against Roman control.

However, the allegiance of the legions changed from a state of Rome to other commanders who headed the army. Soldiers now had a clear financial interest in supporting their generals’ aspirations. 

It became too usual for a general to extend his imperium by using the troops to sway the senators and solidify his authority. Some went so far as to wage war on their political opponents, resulting in civil war.

This eventually resulted in the fall of the Republic and its transition into the Roman Empire, ruled by an emperor. 


Marian legions refer to the cohort divisions of the late Republic and early empire. Following the Battle of Vercellae in 101 BC, Marius awarded Roman citizenship to all Italian troops. 

He excused his actions to the Senate by claiming that he couldn’t distinguish between a Roman and an ally in the heat of combat.

This essentially ended the concept of allied legions. All Italian legions would henceforth be recognized as Roman Legions.

Auxilia, or contingents of allied/auxiliary warriors, would ultimately take over the job of allied legions.

Each legion had an Auxilia (auxiliary) similar to or similar in size, including specialized troops, engineers, and pioneers. 

It also included artillerymen and siege artisans, service and support groups, non-citizens (awarded Roman citizenship upon discharge), and undesirables

There was also a reconnaissance team known as speculatores, who may act as messengers or perhaps as an early sort of military intelligence agency. Each legion included ten speculatores. 

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