Romano-Gallic War: A Clash of Empires in Ancient Times

For centuries, the Gallic tribes of what is now France aided Rome’s enemies and threatened Roman expansion.

Gauls fought with the Carthaginians in the Punic Wars. They were part of Hannibal’s army at Cannae which annihilated a Roman army in 217 BC.

The Romans attempted to work around the Mediterranean through Spain. They were trying to leverage their superior power on land against Carthage. They passed through Gallic lands in northeastern Italy and southern France. Along the way, Gallic tribes aided the North African invaders and resisted Roman advances.

Events Leading Up to the War

For the next century, the Roman Republic, often wracked by civil conflict, gradually pushed the Gauls back. 

However, the fear of the “barbarians” from the north never really faded. The Gauls sacked Rome in 390 BCE. This ever-present fear cemented support for Roman leaders willing to campaign against them, a critical tool in the ongoing competition for power.

Gaius Marius was a young officer in the Roman legions in 121 BC when he took part in the Battle of the Isère River against the Gauls. This battle cemented Roman control over Transalpine Gaul. This was the area between the Alps and Pyrenées that formed the critical land bridge between Italy and Hispania.

Marius is important to this story in several ways. 

In 104 BCE, after defeating the Numidians, the Senate recalled him to Rome to face a threat from two Germanic tribes, the Cimbri, and the Teutones. They marched through Gaul to threaten Roman settlements on the Rhône River. 

These tribes defeated the Roman legions guarding the river at the Battle of Arausio. Marius raised an army to meet the threat, but the tribes disappeared into the mountains of Hispania.

Marius used this time to professionalize the Roman Army. He broadened the recruitment base, created standing units that trained together, and introduced the pilum. By the time the Cimbri reappeared in 102, Marius was ready. 

He led his new army into southern Gaul and defeated over 100,000 tribal warriors with 37,000 legionnaires at the battles of Aquae Sextiae. The Marian reforms reshaped the Roman Army and gave his great nephew, Julius Caesar, the force he would ultimately wield in the Gallic Wars that started 44 years later.

Exiled Gaius Marius sitting among the ruins of Carthage by Joseph Kremer (18th century)

The Rise of Julius Caesar

Born in the same year as his uncle’s victories in Transalpine Gaul, Julius Caesar rose quickly under his family’s mentorship.

However, Marius found himself in conflict with Lucius Cornelius Sulla, one of his former subordinates, during the Social War. After Marius died in 86 BCE, Sulla’s forces triumphed and the young Caesar found himself in a precarious situation.

He found it necessary to leave Rome and join the military campaigning in Asia. He won military renown while serving there and, after Sulla’s death in 78 BCE, he returned to Rome.

By 62 BCE, he was governor of Hispania Ulterior, where he conquered several local tribes and won the loyalty of key legions of the Roman army. He returned to Rome in 60 BCE. He became part of the Triumvirate of leaders that included General Pompey and the banker Marcus Licinius Crassus, that overthrew the patrician government. He set himself up as a man of the people in the image of his famous uncle.

The traditional way that Roman leaders consolidated their power was through military victory. Leaving Crassus and Pompey in Rome, he left for northern Italy. This is where he had several loyal legions stationed and awaited his chance.

One challenge in understanding the Gallic Wars is that so much of it comes from Caesar’s writings. However, these writings were clearly designed as propaganda instruments to enhance his power in Rome rather than an accurate historical narrative.

As Mary Beard points out, “Caesar had a shrewd eye for his public image, and the Commentaries is a carefully contrived justification of his conduct and parade of his military skills.” (p. 283)

Caesar just needed an excuse to begin his campaign for glory. He did not have long to wait.

In 58 BCE, the Helvetii, a tribe in what is now Switzerland, went on a massive raid/migration against the Gallic tribes in France. After defeating the Helvetii later that year at the Battle of Bibracte in 58 BCE, Caesar turned his sights on taking over all of Gaul to eliminate the threat to Roman interests once and for all.

The Wars Begin

The Gauls were not a unified force. There were over a dozen tribes. Some of these were nominal Roman allies against the Germanic tribes and other threats. 

Caesar decided that his priority initially was to prevent the Gauls from being pushed aside by Germanic tribes advancing across the Rhine River. This is what he said openly, but it was clear that he wanted the glory of conquering Gaul to enhance his power in Rome and with the army. 

However, many Romans thought the Gauls were a useful buffer between them and the German tribes, and that conquering all of Gaul would extend the Republic too far.

Shortly after the Bibracte, Caesar got his next opportunity. A Germanic tribe named the Suebi attacked a Roman Gallic ally, the Aeudui. After reports that the Suebians were crossing the Rhine, Caesar advanced into northeastern Gaul and defeated the Suebians at the Battle of the Vosges. 

His much smaller force drove the German tribes back across the Rhine and ended their threat to Gaul for the time being.

Wars in Belgium and Along the Coastline

The Gauls were unnerved by Caesar’s conquests. They began raising troops to oppose him the following year.

Looking for opportunities, he intervened in another conflict among the Gallic tribes. This time, his gaze fell on the Belgae, a confederation of tribes living in what is now Belgium. They attacked a Gallic tribe allied with Rome and he used this as a pretext to march on them.

Modern Roman combat techniques, particularly their siege skills, took the Belgians by surprise. He defeated the dominant tribe, the Suessiones, by taking their main fortification with relative ease.

The scale of the defeat caused many other Belgian tribes to surrender. Only the Nervii, the Atrebates, and Viromandui remained in the field. Caesar defeated them at the Battle of Sabis when they attempted to ambush his forces setting up camp.

Reaching the coast, he attacked another Belgian tribe who he accused of violating the terms of their surrender. Caesar punished the tribe by selling 53,000 of them into slavery. This made him wealthy and it liberated him from the banker Crassus’s loans back in Rome.

In 56 BCE, the Veneti, a tribe in Brittany, refused Roman demands for food and they took several emissaries hostage. This was a provocation that Caesar could not let stand.

The last tribes to fall were those in Brittany, who relied on a navy built to withstand the Atlantic swells to stymie Roman advances in the area. This campaign turned out to be a naval struggle that resulted in the Veniti defeat at the Battle of Morbihan. After Caesar destroyed their fleet, the Veneti surrendered.

During 56, Caesar’s other generals mopped up the remaining hostile tribes in Normandy and the Aquitaine. These campaigns effectively ended active Gallic military resistance to Roman rule.

Crossing the Rhine and the Campaign in Britain

After securing most of the Gallic heartland, Caesar looked for new targets to increase his prestige in Rome. The campaigns of 55-54 BCE can be viewed as publicity stunts.

First, he employed superior Roman engineering to build a bridge across the broad River Rhine. He became the first Roman general to enter the Germanic lands to its east. This campaign lasted just 18 days and had little effect other than on his prestige back home. The Germans retreated into the dense Black Forest.

Caesar wisely chose not to follow. This probably saved himself from the fate of the Roman legions that were wiped out there almost a century later. Instead, he took advantage of the defenders’ absence to raid and plunder before withdrawing back across the river, destroying the bridge along the way.

Using the naval technology he constructed and adapted from the Veneti, Caesar turned his sights on Britain in August. He launched a force of two legions across the channel. Like the Rhine crossing, this was an audacious move designed as a publicity stunt.

It did not go well for him. Storms beleaguered his ships. His cavalry did not make it across the channel. Those forces that did land on the British coast were forced to withdraw after skirmishes with the Briton tribes. 

However, Caesar learned a lot about this mysterious land at the edge of the world and how the Briton tribes fought. He would prepare his next invasion much more carefully.

It is unclear if he ever had a real thought of taking over Britain, but he could not let a defeat stand because of his need to always appear victorious. 

He returned in 54 BCE with three to four times as many troops. In a series of battles, he forced the Britons to sue for peace. While these agreements were unenforceable after the Romans left the island, Caesar could announce another audacious victory back in Rome.

The British expedition marked the end of active campaigning in Gaul for the short term. The Roman forces spent the next two years putting down revolts among various Gallic tribes. These tribes objected to providing tribute and provisions to the Roman troops stationed there. 

This attritional warfare led to a punitive campaign in 53, which Caesar directed against the civilian population.

While he was engaged in these efforts, however, things did not remain quiet for Caesar at home. He was forced to return to Rome to deal with political matters and shore up his position there, leaving his best troops in Gaul.

Vercingetorix’s Revolt

Sensing an opportunity, Vercingetorix, a leading Gallic chieftain, united several tribes in revolt. He assembled an army to take on the Roman occupation. At first, he enjoyed significant success by attacking areas that the Romans could not defend, pillaging and sacking several Roman and allied settlements.

Caesar recognized the threat. He was a slave to his propaganda in Gaul as much as he was in Rome.

The Roman forces available to control the country never numbered much more than 50,000 legionnaires. If the Gallic tribes united against them, they could field many times as many warriors. This is precisely what happened as Vercingetorix, a shrewd leader, counted on.

Caesar knew that the only way to defeat the resistance was to decapitate it. Therefore, he concentrated his forces to defeat Vercingetorix in the field. The Gallic chieftain was forced to defend the fort of Avaricum for political reasons. Caesar defeated the Gallic forces and took the town.

Caesar pursued the Vercingetorix to the provincial capital of Gergovia and laid siege to it. The Roman general recognized that the key to any siege was cutting off his opponent’s supply, and this became the focus of his actions.

After an initial victory, they cut the supply lines. Caesar sent his forces to attack the Gallic lines but did not intend to press his attack. Caesar knew that Vercingetorix’s army lurked in the hills around the fortification. He knew he was ready to cut off any forces pinned against the walls.

However, part of his force did not get the withdrawal order and was enveloped by the Gauls emerging from the hills. After suffering heavy losses trying to rescue these troops, Caesar was forced to withdraw from the field and regroup. This was a major propaganda victory for Vercingetorix, and more Gallic tribes rallied to his cause because of it.

Caesar withdrew into what is modern Alsace, with Vercingetorix in pursuit. However, the Roman forces were once again able to repulse the Gauls in open combat. Despite his superior numbers, Vercingetorix retreated to the hilltop city of Alesia and awaited the reinforcements he knew were coming.

Caesar pursued him and immediately began a siege of the well-defended town. And unlike Gergovia, Roman forces completely encircled Alesia. Caesar did not feel compelled to attack as he had already cut off the Gaul’s resupply.

Instead, he once again relied on Roman engineering acumen and constructed a wall 8 miles in circumference around the city.

A relief force, at least as large, if not significantly larger than that trapped in Alesia, was on the way. Knowing that this force was on its way, Caesar constructed a second wall outside of his own forces. This wall was 15 miles in circumference.

The Roman forces were effectively enclosed within a doughnut of walls encircling Alesia. This daring strategy put the Roman legions in a position of fight or die.

What was shrewd about this was that Caesar could fight a defensive battle against both sides. Attacking defended positions always requires a great superiority in numbers, especially with forces that lack siege equipment like the Gauls.

By the time the relief arrived, Vercingetorix’s forces within Alesia were in a desperate state as their supplies ran out. They expelled the civilians from the town and demanded that the Romans let them pass, which Caesar refused.

Over the next few days, thousands of them died in the fields between the Gallic and Roman walls. However, this action showed Caesar just how desperate the Gallic position had become within the city. Time was on his side.

He knew that neither Gallic force could wait for long before attacking the Roman-prepared positions. Commius, Vercingetorix’s cousin, eventually arrived with reinforcements, but his initial attack was repelled with heavy Gallic losses.

Instead, Commius sought weak points in the Roman lines. Several days later, both sides coordinated an attack that pushed the Romans to their limits. However, just as the Roman lines were breaking, Caesar sallied forth with a force of mercenary German cavalry. He circled behind Commius’s attacking forces, forcing them to withdraw.

On the inner line, Vercingetorix’s weakened forces, attacking at the same time, could not break through the Roman defenses. He withdrew back into the city.

With his food supplies running out, Vercingetorix and his fellow chieftains surrendered the next day. The Romans also captured Commius,. The surviving relief forces evaporated into the hills after the failed attack.

Caesar returned to Rome in triumph. Upon his arrival, he paraded the captured Gallic chieftains through the Forum.

Several Gallic tribes held out after Alesia, but they were divided and mopped up by Caesar’s forces over the next couple of years. The Gallic Wars were effectively over by 50 BCE.

Vercingetorix Throws Down His Arms at the Feet of Julius Caesar, 1899, by Lionel Noel Royer

The Aftermath

By this point, Caesar’s victories transformed him into a populist hero. He overshadowed his two colleagues on the Triumvirate and sought to turn his victories into absolute power in Rome.

Caesar often risked his own life and led his troops to victory after victory. This is how he won the loyalty of the troops over many battles, which made him an almost unstoppable force.

Pompey, a general in his own right, rallied forces to oppose Caesar. At first, Caesar attempted to use political means to gain the upper hand.

Eventually, he felt compelled to take the unprecedented action of marching his armies from Gaul toward Rome. This started the Roman Civil War, which Caesar ultimately won and ended the Roman Republic.


Beard, Mary. SPQR: A History of Ancient Rome (New York: W.W. Norton). 

Cowley, Robert and Geoffrey Parker eds., The Reader’s Companion to Military History (New York: Houghton Mifflin, 1996)

Keegan, John, A History of Warfare (New York: Vintage, 1993)

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