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In his Life of Julius Caesar ancient biographer Plutarch describes Caesar’s Gallic campaigns as a beginning for the conqueror—the first and greatest step on his path to power and immortal fame. The subjugation of Gaul showed him superior to Rome’s greatest military commanders. His mettle was tested and proved in nearly 10 years of successful operations in difficult terrain, navigating shifting alliances and counter-alliances, confronting and conciliating savage enemies and perfidious allies, and producing victory repeatedly through determination, imagination, and audacity. He fought more battles and killed more enemies than any of his predecessors. Through battle and siege, he subdued nations, slaying a million men and capturing a million more, bringing vast territory under Rome’s control.

But Gaul was not an end in itself. Although the stage of Caesar’s exploits was beyond the Alps, his audience was Rome. Military service had long been requisite for Roman political office. Successful military command was a potent aid in attaining the highest positions. In the late Republic, it increasingly became the means of acquiring extra-constitutional authority as the sword became the arbiter of power. 

A Political Opportunity

Caesar was already involved in this game when he entered Gaul in 58 BCE. Two years before he had formed a political alliance with Gnaeus Pompeius Magnus and Marcus Licinius Crassus, called the First Triumvirate, that allowed them to control the entire Roman political system. Caesar knew the arrangement could not last forever. He had to prepare for the inevitable showdown. He needed the opportunity to increase his fame and influence as well as cultivate the intense personal loyalty of his troops that would allow him to challenge Pompey. Gaul was his training ground. 

Moving across Gaul, Caesar led his troops, portrayed here by reenactors, to a series of stunning victories. (Patrick Aventurier/Getty Images)

To maximize the political benefits of his exploits in Gaul, Caesar wrote his own account. Just as he used the war in Gaul to gain the power and influence necessary to bend Roman politics to his will, he used his narrative to enhance his reputation toward the same end. The Gallic War, based on his notes, diaries, dispatches, memoranda, and reports to the Senate embellished with added content and literary flourish, highlights Caesar’s abilities and achievements. While many historians suspect it was exaggerated for the author’s benefit and is propagandistic rather than strictly historical, it is our primary source for the conflict.

Caesar’s account famously begins by describing Gaul as divided into three parts inhabited by the Belgae, the Aquitani, and the Gauls. This simple mental map becomes far more complicated as the annual campaigns are narrated. The work ultimately mentions more than 100 tribes Caesar must defeat or pacify. This ethnic diversity overlays a challenging topography marked by rivers, swamps, mountains, and vast, trackless forests magnifying the difficulties of logistics and maneuver—and punctuated by nearly unassailable strongholds.

From a Roman perspective, Gaul was tribal, atavistic, chaotic, and dangerous.

Its specter of fear haunted for centuries after the Gauls sacked Rome in 390 BCE. Already in control of Cisalpine Gaul, the area of Italy north of the River Po, Rome added Transalpine Gaul as a province in the second century BCE. This territory was often called Provincia Nostra or simply “the Province,” whence derives the name for the modern French region Provence. These territories and peoples were heavily influenced by Roman culture and involved in trade with Rome, imbibing the benefits of its civilization. This Romanization was reflected in the name Gallia Togata (toga-wearing Gaul). The farther one traveled, the weaker this Roman influence became. The Romans called these untamed lands Gallia Comata (long-haired Gaul), evoking the wild, freedom-loving character of their inhabitants. 

As part of the Triumvirate’s division of political spoils, Caesar was appointed proconsul of the provinces of Illyricum as well as Cisalpine and Transalpine Gaul in 58 BCE. Before him stretched a vast field of opportunity, and he meant to make the most of it. The years that followed were marked by numerous successful campaigns and a constant stream of victories enhacing Caesar’s reputation.

Gaul became an endless gift to Caesar. The restless stirrings of Gallic tribes against Roman domination ensured constant conflict, yet the Gauls’ disunity and inability to put common interest over local loyalties meant that Caesar could deal with them in a largely piecemeal fashion. 

But eventually, Caesar’s successes would forge a new enemy—spurring a leader to arise among the Gauls capable of forging a unity among the tribes not realized before. This leader’s name was Vercingetorix. He would confront Caesar with his greatest challenges yet.

A New Enemy

If Gaul seemed tranquil in the beginning of 52 BCE, it was only the calm before another breaking storm. Beneath the snow-laden trees and in the recesses of shadowed hills, secret meetings were held to commiserate about the misfortunes of Gaul and call for a united effort to drive the Romans out. The moment seemed favorable. Not only had Caesar withdrawn beyond the Alps, as he habitually did in winter to be closer to events in Rome, rumor alleged that he was tangled in political turmoil that would prevent him from joining the troops he had left to garrison Gaul. Solemn oaths were sworn and swords were sharpened. 

The first stroke fell upon Cenabum, where Roman traders were massacred, and their goods looted. Like embers carried by swift winds, the news spread quickly. Vercingetorix, the newly-proclaimed king of the Averni, seized the moment to forge the necessary unity among the tribes. Calling upon all to uphold the oaths they had sworn, he combined exhortation and severity to forge an army with which to oppose Rome and over-awe the tribes who hesitated. By common consent, he was given supreme military command. 

Receiving word of these events, Caesar hurried to Transalpine Gaul only to confront an immediate difficulty. The Province was under threat, but the bulk of his forces were still in winter quarters, far to the north. If he called them south, they would be harried all the way, yet to march to them was equally dangerous. Using surprise, misdirection, and maneuver, he forced the enemy to shift position and was able to unite his entire field army under his command. 

But Vercingetorix was a wily general who understood his enemy’s challenges as well as his own. The keys to controlling territory in Gaul were the fortified towns called oppida, which could function as anchors of strength and supply or as hostages to force an opponent’s hand. He besieged Gorgobina, a chief center of the Boii who, along with the Aedui, were allied with Rome. This forced Caesar to choose between two undesirable alternatives: conveying weakness to allies and surrendering the initiative or moving before spring and risking major problems of transport and supply. Caesar chose to march. 

New Rules of War?

Caesar’s decision worked toward solving both problems at once. He quickly took three villages rich with supply and caused Vercingetorix to abandon the siege. Recovering the initiative, Caesar marched toward the hostile town of Avaricum, the most important stronghold of the Bituriges, hoping its capture would subdue the surrounding territory. But the old rules would no longer necessarily apply. 

Caesar was a good military engineer, devising a system of barriers and booby traps during the fateful siege of Alesia. (Ivy Close Images/Alamy Stock Photo)

Vercingetorix had a new kind of war in mind. Convening a council, he presented a strategic vision to the Gauls that would require patience, forbearance, and self-sacrifice in the national cause. He outlined an asymmetric strategy that would avoid direct assault, focusing instead on strangling Roman forces by preventing them from foraging and gathering supplies. Victory would be won by attrition.

The advantages in such a war fell to the Gauls, who were operating in their own territory. There were no ripe harvests in the early season to sustain large infantry forces, which meant the Romans would have to go looking. An abundance of Gallic cavalry would enable them to isolate and destroy the foraging parties. To maximize the effects of this strategy, he called for scorched earth. Villages, towns, farm buildings, food, supplies—anything they could not carry with them was to be destroyed before the enemy could take possession. The Romans would have to travel farther in search of food, increasing their vulnerability. 

Preparing For a Siege

Flames sprang up in all directions. Such a strategy was not easy to carry out because it called for the destruction of one’s own. The Bituriges begged the others to spare Avaricum, the finest city in Gaul. It was eminently defensible, they argued, as it was surrounded almost completely by a river and a swamp. The sturdy walls fostered hope that the Romans could not take it by force of arms. Vercingetorix argued against this exception, but the tide of sympathy was against him. Nonetheless, he would not commit his field army.

The townspeople would be left on their own. After all, if Avaricum fell, it would only vindicate his tactics. Caesar began preparations for a siege while Vercingetorix watched from a distance.

In addition to trenches, earthworks and booby traps, Roman troops at Alesia constructed a palisade with parapets and battlements, plus siege towers which they used as platforms to fire catapults. The Gauls maintained fierce resistance. (DeAgostini/Getty Images)

With his options limited because of difficult terrain, Caesar began constructing an earth ramp and two siege towers. The threatening presence of the Gallic field army lurked in the hinterlands, ambushing foraging parties. Shortage of food, cold temperatures, and steady rains added discomfort to an already arduous task. Moreover, the Gallic defenders were both energetic and inventive. They undermined the siege ramp by digging tunnels, raised the height of their walls and towers, made frequent sallies to set fire to the siege works, and cast heavy stones on the working legionaries. 

Despite these challenges, the Romans completed the ramp in 25 days.

The Gauls made one last great effort to forestall the storming of the town. They launched sorties and hurled incendiaries onto the siege towers and ramp. But Caesar had foreseen the danger. Although it was the middle of the night, Caesar’s policy of stationing two legions outside the fortified camp and remaining near the construction site himself enabled him to react quickly and decisively. The fires were put out and the enemy pushed back.

Caesar Changes His Plan

Seeing that they could not hold out, the Gauls resolved to abandon the town. They hoped to escape to the camp of Vercingetorix during the night. As they prepared to flee, the women, fearing they and the children could not escape, begged the men not to leave them to the enemy. When the women’s pleas were ignored, they began calling out and gesturing to the Romans. This put the Romans on the alert. The escape plan had to be abandoned.

The next day the blow fell. The siege towers rolled forward, and the Romans poured onto the wall. The defense collapsed in panic. The Romans, desiring revenge for the massacre at Cenabum, made no distinctions of age or sex and gave no quarter. Of 40,000 inhabitants, hardly 800 escaped. Vercingetorix showed himself equal to the moment, using the disaster to reinforce his strategy, win over the remaining Gallic nations, and increase his army.

Caesar was also making use of events. Having captured a large amount of grain and other supplies, he refreshed and restored his army for a spring campaign. But his difficulties stretched beyond the battlefield. Envoys of the Aedui arrived to urgently request his help in resolving an internal dispute over the leadership of their nation. Reluctant to postpone the campaign, the potential consequences of civil strife within so important an allied people could be devastating. Caesar altered his plans. Settling the dispute according to their national laws, he sought to restore their unity and remind them of their allegiance to him. 

Ordering a levy of 10,000 infantry and all available cavalry, he then marched in search of Vercingetorix. Caesar knew that a war of constant maneuver and attrition did not favor him. He had to destroy the Gallic field army. As a means of provoking decisive conflict, he marched into the lands of the Averni themselves, targeting Gergovia, their capital. Vercingetorix was compelled to shadow him.

For days the two armies marched and camped within sight of each other on opposite banks of the Elaver River. Gergovia was strongly situated on a very high hill, with the elevated ridge in front of the town thickly covered by the camp of the enemy. Undaunted, Caesar first built a large, fortified camp. He then seized and fortified a lower hill, stationing two legions there and joining the camps by parallel trenches. The Gauls watched the methodical industriousness of the Romans with uneasy eyes. 

Traitors In Their Midst

Vercingetorix had other weapons to wield than those visible upon the field. He made use of bribery and collusion. Leaders of the Aedui turned against their Roman allies. One of them was the commander of the infantry force Caesar had called to his aid; this man employed lies and fearmongering to convince his men to attack the Romans. Caesar managed to restore the loyalty of the troops without battle and received the deepest apologies from Aedui envoys.

However, the episode made the Roman leader increasingly uneasy about traitors in his midst and the prospect of being surrounded by a larger Gallic uprising. He began considering how to withdraw his army from Gergovia to more favorable ground—without giving the impression he was fearful.  

An opportunity presented itself when, in response to Caesar’s misdirection, the bulk of the enemy force was employed fortifying a western approach to the town, leaving their camp virtually empty. A swift, stealthy attack delivered the camp into his hands. This is apparently all he intended. The retreat was sounded. But many of Caesar’s troops did not hear the signal. Carried away by hopes of swift victory, they assaulted the town itself. An alarm caused the bulk of the Gallic forces to rush back through the town to engage the Romans at the wall.

As their numbers increased, they gained the advantage. The Romans were driven off with heavy losses. When they rallied on the plain to face their pursuers, the Gauls would not engage, nor could they be tempted to do so for the next two days. Such restraint indicated that the message of Vercingetorix was having an effect.  

Caesar showed ingenuity at Alesia, building a wall around the enemy fortress plus another wall to protect his besieging troops. (Department of Classical Studies, Dickinson College)

Caesar’s failure to take Gergovia increased Vercingetorix’s reputation and further loosened Caesar’s hold upon his allies. The unrepentant “traitors” among the Aedui looted and burned a key supply cache at Noviodunum. Refusing to take an embarrassing and backward strategic step, Caesar did not withdraw into Transalpine Gaul. Instead, he went on the offensive, surprising the enemy with quick movement and risky river crossings to seize what he needed. Knowing he could not expect relief forces from the south, he hired Germanic horsemen from across the Rhine to supplement his forces.

A Gamble Worth Taking?

Over the next few months, Vercingetorix collected a considerable force, increasing the threat to the Province and drawing Caesar closer. His marked superiority in cavalry convinced Vercingetorix that the opportunity for a decisive attack was at hand. But his aim was still a strike against Roman logistics rather than a general engagement. Dismissing the ability of the Germanic cavalry to stop them, he convinced the other Gauls that by attacking the Romans while they were burdened by their baggage and strung out in column on the march, they could severely weaken them. Yet Vercingetorix underestimated Roman cohesion and discipline. 

Caesar adroitly managed both to secure his baggage train and to inflict heavy damage on the enemy. Reeling back, Vercingetorix withdrew into the nearby oppidum of Alesia. This move seems a departure from Vercingetorix’s previous strategy. He had now allowed himself to be pinned down and be subjected to Roman siege warfare, at which they excelled. On the other hand, sending his cavalry away on the mission of recruiting a massive relief army can be seen as the capture of a unique opportunity. If they could hold out, Caesar would be crushed between two forces. It was perhaps a gamble worth taking. But the price of failure would be high.

Settling in for the siege, Caesar built a system of fortifications of extraordinary size and complexity. His fortifications enclosed the defenders within Alesia (circumvallation) and guarded against assault from without (contravallation). An initial trench 20 feet wide was dug on the plain to discourage attacks on the working parties. Behind this obstacle two more trenches were dug and filled with water diverted from the river that flowed across the plain. Behind these ditches, a wall of earth and rubble was raised, crowned with a palisade, reinforced with parapets and battlements, and guarded by towers that served as firing platforms for catapults.

Mechanized Artillery

But the 11-mile circuit stretched his lines thin, particularly during the construction phase. Thus Caesar added a system of hidden obstacles and traps in front of the walls and trenches so that the fortifications could be defended by smaller numbers. Triple rows of sharpened wooden stakes covered pits. Barbed iron spikes would not only cause casualties but slow any assault so that the Romans could concentrate force against it. Caesar had an identical line of fortifications built facing the other direction to guard against the relieving army.

After an initial unsuccessful attack when the relief army arrived, the Gauls spent the next day preparing to assault the Roman fortifications. They constructed wicker screens to cover the trenches, grappling hooks to pull down the parapets, and ladders to scale the palisade. In the middle of the night, they raised a mighty shout to signal those besieged in the town and launched their attack.

Hearing the clamor, Vercingetorix led his forces out to attack the Roman interior lines. His hopes must have been high, but the shouts of his rescuers quickly turned to screams of pain. As they rushed forward in the darkness, iron spikes pierced their feet. Sharpened stakes impaled them as they fell into the hidden pits.

While the Gauls launched an initial barrage of missiles to drive the Romans off the parapets, they came under the murderous fire of Roman mechanical artillery firing stone shot and heavy bolts. Even without precise aim in the darkness, these did great damage to the massed ranks of the attackers. By the time Vercingetorix’s forces had negotiated the first trench, the attack had failed. 

Vercingetorix surrendered willingly to Caesar following defeat at Alesia. Dramatic depictions of his surrender were inspired by an account by Plutarch. After being imprisoned for over five years, he was ceremonially killed in Rome. (Musée Crozatier, Le Puy-en-Velay)

Repelled twice with heavy losses, the Gauls considered what to do. Because of the difficult terrain, Caesar’s fortifications were not completely uniform. The Gauls saw an opportunity in a gap to the north of the town created by a hill too large and steep to be encompassed by siege lines. The gap was guarded by a Roman camp holding two legions, but it was on unfavorable ground and constituted a weak point. The Gauls secretly dispatched a force of 60,000 men. A stealthy night march put them behind the hill before dawn, where they waited until the appointed hour. Gallic forces on the plain gathered to divert Roman attention. The assault was launched around mid-day. 

The Crucial Moment

From his vantage point in Alesia, Vercingetorix saw these movements and prepared to launch his own supportive assault from within the lines. But his was not the only eye surveying the field. Caesar had set his own camp on the high ground south of the town for a clear view of the scene. The Romans were now under assault in multiple locations and from two directions.

This was the crucial moment. The struggle in the north was particularly bitter. Exhausted legionaries were in danger of being overrun by relentless and determined Gauls. Caesar dispatched six cohorts to plug the gap while riding out to encourage the troops holding the line on the plain, his purple cloak announcing his presence to friend and foe alike. His personal intervention turned the tide. The line held. But the battle could still be lost. Calling upon four cohorts and available cavalry, Caesar rushed toward the crisis point.

Seeing their commander’s approach, the Romans resisted with renewed energy. Desperate to break through before Caesar’s arrival, the Gauls attacked wildly. But Caesar had divided his cavalry. One half rode with him; the other half he had sent to circle around and attack the enemy from behind. When the Gauls became aware of this second force, they broke and turned to flee. Most were run down and slaughtered. Vercingetorix’s plan was a near stroke–but the Gauls had lost. Those inside withdrew back into Alesia. Those outside fled from their camps and dispersed to their various nations.

Caesar’s victory was decisive. The 74 enemy military standards brought to him testified to the magnitude of his success. Several key enemy leaders were killed or captured. Vercingetorix surrendered himself to the conqueror in order to preserve what remained of his people—held captive in Rome for five years, he was ritually garroted in 46 BCE during Caesar’s much-delayed “triumph” ceremony in the Roman capital. Alesia marked the end of general, organized resistance to Rome. Though Gaul was not yet completely subdued, it was effectively conquered.

this article first appeared in military history quarterly

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