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  • James Houser

102 BC - Gaius Marius, his Military Reforms, and the Germanic Invasions

Updated: Jun 12, 2021

JULY 27 - 102 BC. After a string of terrible Roman defeats, Gaius Marius and his new model Roman army confront a massive host of Germanic tribes hellbent on invading Italy. At Aquae Sextiae, Marius and his legions will save Rome. Their story, though, is less a tale of battle and more a tale of political and social upheaval similar to our own times. The Romans win, but the Roman Republic is doomed.


Before there was a Roman Empire, there was a Roman Republic. A Senate composed of the old noble families of Rome controlled the functions and government of the city-state of Rome – a city-state that by 100 BC was much more than just a city. The Senate obeyed a strict set of laws, enjoyed a great amount of privilege and dignity, and overall were the “leading men” of Rome. While many men down to the lowest farmer could be a Roman citizen, it was something else to be a Roman senator. The Senate was extremely hostile to political power and privilege being held by anyone but them and the lower nobility, known as the Equites.


The Senate did not just sit on their benches and send other men to fight, however. The Senators took an active part in the defense of their country, serving as high to middle-ranking generals in every Roman campaign. The citizens of Rome annually elected two Consuls – the executive branch of the Roman Republic – who would only serve for that year, and would be banned from serving again for five more years. The Consuls were almost always sitting Senators or high nobles. This was the Roman way of keeping too much power from falling into the hands of one man. Only rarely did Rome appoint a Dictator, and only for a six-month period, in times of great emergency.


Whether Rome realized it or not, an emergency was coming. By 105 BC, the Roman Republic had ballooned far outside its original boundaries, and the old systems of government were becoming more and more unstable. There is a saying that “Rome conquered the world in self-defense,” and while it’s not quite true it has a grain of truth. Over the last few centuries, Rome’s power had first expanded throughout Italy, then into the Mediterranean. In the wars with Carthage they conquered most of Spain and North Africa. In wars with the Greeks they subdued the Balkans. Their armies ranged into Turkey and southern France. The Roman Republic was still the form of government, but the Republic had gained an empire along the way – so that’s what I’m going to call it.


The foot soldiers who had conquered this land were the Roman citizenry. Rome had always based its military on a sort of citizens’ militia, a conscription of farmers to fight for the Republic against its enemies. Only a Roman citizen could serve in the Roman maniple, with its three infantry classes of hastate, principes, and triarii. To be eligible for conscription, a Roman citizen had to have property of a certain worth, provide his own equipment, and had to be a taxpayer.


In the early days, when Rome’s enemies were a few days’ march away and before the conquest of an Empire, this had been a very good system. By 105 BC, though, the farmers of Rome had to march farther and campaign longer, possibly for years. As a result their lands went untended, their families fell into debt and were sold into slavery, and their lives were destroyed by the constant military campaigning. Soon the number of eligible men began to decline sharply due to the economic and social changes brought on by the Republic’s wars. As the small farmers that had made the Empire strong began to disappear, the Roman armies began to disappear with them.


The growth of the Empire brought enormous changes in the Roman society, economy, and political system. The addition of vast new lands, great quantities of wealth, and masses of barbarian slaves poured in and made Rome wealthy and powerful beyond any previous measure – but most of this wealth poured into the pockets of a relative few. The Senators and the lesser nobility reaped the rewards of Roman victory, even as the larger citizenry paid the price for those victories. The Roman upper class used their vast wealth to buy up the small farmers’ properties, turning Italy into a huge network of estates tended by thousands of slaves from Gaul, Spain and Africa, and owned by a very few. They were not just the 1%...they were less than 1%.


As the disenfranchised lower classes of Rome flocked to the cities, the Republic found it harder and harder to raise the troops they needed for further wars. Fewer and fewer citizens could meet the tax requirement, pay for their own equipment, or owned any property. This started to be a real problem by the 100s BC, when Rome was faced with a pair of emergencies.


The first emergency was Jugurtha. This King of Numidia – modern-day Algeria – had murdered his brother, a Roman ally, to seize the crown and launched a guerrilla war against the Roman occupiers. Rome had enormous trouble trying to scrape up willing volunteers for this campaign, especially since every Roman had to worry about being impoverished and his family going hungry during a long tour of duty in Algeria.


The second was the Germanic invasion. Two enormous tribes from the north, the Cimbri and Teutones, were on the move – and rumor had it that they were making a beeline for Roman territory. In 113 BC, they threatened a Roman-allied tribe; when the Romans sent a force to help, the invaders overwhelmed them and inflicted a devastating loss. In 109, they repeated the process, and again in 107. The Romans had lost three battles to this huge, threatening Germanic force, and there was good reason to fear that they could not stop them.


The Numidian War had been going on for several years when the Senate swallowed their pride and elected a man named Gaius Marius as Consul. Gaius Marius was what was known as a “novus homo” – a “new man.” He did not come from the noble families; his father, although a Roman citizen, was a laborer from a small village. He had joined the Roman army as a young soldier, but soon revealed his burning ambition and zeal for achievement. He built up a military record of such accomplishment, and made enough of the right friends, that he soon began to climb the political ladder. He was also, unusually and dangerously for Rome, a committed populist. He advanced laws that restricted the influence of the wealthy, even as he married into a noble family (none other than the Julii – he married the unborn Julius Caesar’s aunt) and used the wealth he gained from this maneuver to advance his military career.


Marius served in the Numidian War in North Africa as a junior general, and was harshly critical of his commander. Marius was a popular general, who ate with his troops and endured their hardships, and it was due to his status as a soldier’s general and as a man of the people that he had risen. In 107 BC, with Rome facing two emergencies and desperate for anyone who could promise to solve their problems, Rome elected Marius as Consul.

Marius realized that to survive, Rome would have to undergo drastic political changes. What he instituted, on a small scale for the Numidian War at first and then on a much larger scale, came to be known as the Marian Reforms. These dramatic changes to Rome’s political and military structure of Rome would have massive unforeseen consequences, but Marius used the emergency to push them through. It was the Marian Reforms that built the Roman army we know from film, art and literature – but the cost would end up being high.


The old Roman manipular system had based military service on the shrinking number of citizens who owned X amount of property, could supply their own arms, and paid taxes. Marius removed all these restrictions, opening up military service to the landless masses of the Roman people. Because these poor citizens could not supply their own gear, Marius provided them with arms and armor at the state’s expense. Relaxing the property requirement and providing state-funded equipment greatly enlarged Rome’s armies overnight, at the expense of the Republic’s long-held traditions and values. Even more radically, Marius allowed Italian allies to enlist and fight for Rome in exchange for full citizenship.


Marius also transformed the Roman army in another way. Instead of units being called into service as needed, and then disbanded after temporary service, he established permanent legions that formed a standing army. Drill and training would take place all year round and the ranks would be filled with career soldiers, thus turning the Roman Army into the most highly trained and disciplined army in the ancient world. Finally, Marius introduced legislation into the Senate that offered land as a retirement benefit for the Roman soldier. Rather than the vast expanse of conquered real estate going to the 1% and their cronies, it would go to the men who had fought and bled for it.


This package of reforms sounds like common sense to us – but to Rome in 107 BC, it changed the entire political dynamic. A Republic that had placed the military power in the hands of its wealthy and well-to-do citizens for centuries gave the unwashed masses the privilege of fighting in Roman wars, and men flocked to the banners. A Republic that had cherished the notion of a man fighting to defend his own fields had given swords and armor to men who fought for plunder and profit. Marius was the most popular man in Rome, and a skilled military leader – a dangerous combination. He had done what was necessary to rebuild the Roman armies and save the Republic from complete military disaster, but at the cost of some of its oldest traditions and values.


Marius turned his new army into a well-oiled killing machine, drilling and disciplining them relentlessly. They were now truly organized into permanent fighting units, which Marius called “legions,” and it was these men that Marius led to North Africa to end the Numidian War. He beat the North Africans in several battles, captured their King Jugurtha, and in 104 BC brought him back to Rome in chains. Marius celebrated a glorious parade and triumph through Rome, even as bad news arrived from the Roman border to the north.


Quintus Servilius Caepio was the Consul for 106 BC, a greedy and arrogant Senator who neglected military duties and sought to undo Marius’s reforms by restricting the power of the lower classes. He raised a military force by the old system, and took this army into southern Gaul to challenge the marauding Germans. Confronted at Arausio in 105 BC by 200,000 Cimbri and Teutones, Caepio badly handled his 80,000 Romans. The result was a catastrophe, with the entire Roman army being wiped out in their worst defeat since Cannae, and the Germans rampaging on to plunder Spain and Switzerland.


With this news, the terrified Roman people elected Marius Consul again in 104 BC, and again the next year. And the next year after that. In all, Marius would serve an unprecedented seven terms as Consul, more than any Roman before or after. The conservative Senators were terrified of his dominance in the Roman Republic, but most Romans just wanted him to save them from the terrifying Germans.


In 102 BC, the Germanic tribes returned, and this time headed for Italy itself. Once again, Marius swept the poor and downtrodden of Rome into the ranks and outfitted them lavishly at state expense, and once again led them north. After a series of preliminary engagements, Marius finally confronted the main body of the Teutones at Aquae Sextiae, near modern Aix-la-Provence in southern France.


Marius chose a site for the upcoming battle, taking position on the high ground. He steadied his trained but inexperienced men, leading from the front as always. As the battle began, the Teutones – numbering nearly 200,000 in their tribal coalition – charged Marius’s 37,000 Roman legionaries, bellowing like beasts and blowing their shrill horns. They charged up the hill, where Marius’s new model Roman army met them with the crunch of steel and flesh. Their short swords tore through the German packs, discipline and training telling true. Marius rode behind the lines on his horse, shouting encouragement at his men and taunts at the Germans.


Finally, the Roman legion began to drive the Germans back down the hill. As they did so, Marius gave a predetermined signal, and an ambush force of Roman cavalry swung out from behind a dense forest and hammered into the German flank. The barbarians broke ranks and fled, but there was nowhere to go. The Romans hunted down and killed or captured every man in the tribe, and these captives – along with the women and children of the Teutones – were all sold into slavery.


The next year, 101 BC, Marius repeated the performance and crushed the Cimbri at the Battle of Vercellae, once again triumphing over enormous odds. Rome went wild with relief; the vast barbarian hordes had been somehow defeated by the Roman Army of plebeians and their “new man” general, a man with no pedigree or nobility. Marius was awarded yet another triumph, and in 100 BC assumed his unprecedented sixth Consulship.


So all was well, right? That’s a good ending to the story.


Of course not. For Marius had, by taking advantage of his immense political and military power to totally upend the Roman state, opened the floodgates. The Marian Reforms had made the Roman Army the ancient world’s greatest killing machine, a force unequalled in lethality and organization until the 1800s. Out of the decaying army of the Republic, the phoenix of the Roman Legions would become a synonym for victory, discipline, and inevitability even to this day.


There was a poison pill in Marius’s reform, though. By decoupling the Army from the Senate and the organs of government, the loyalty of the Legions was no longer to the state – but to their general. Marius became the most dangerous man in Rome, and over the next twenty years he would be at the epicenter of revolution, civil war, and chaos throughout the Roman Republic. This chaos would not end until Julius Caesar, Marius’s nephew and the most successful of all the men to fill his shoes as a victorious general with political ambitions, ended the Republic completely.


The transformation of the Roman Army led unmistakably to this point.

The desire for civil rights...the growing economic disparity between the rich and the poor...plague and disease...the constant state of fear brought about by warring political factions...growing external threats...the yearning of the unheard masses...rioting and chaos in the streets...the belief in miracle men who could solve their nation’s problems…

…all this led to the rise of military dictators, backed by armies that now had a direct financial incentive to back their generals’ growing ambitions, who saw the route to power in armed struggle.


Good thing none of those problems are around today.


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