Battle Of Alesia

Battle Of Alesia

Roman Empire
The Roman world in 58 BC, before Gallia’s conquest by Caesar. CC BY-SA 3.0

“In this Caesar there are many Mariuses.”

Siege Of Alesia: Caesar Finishes Off the Gallic Wars In early 52 BC, Julius Caesar’s divide and conquer strategy finally came undone when the tribal leader Vercingetorix finally united the tribes behind him. Caesar had spent the previous year subduing the rebellion of Ambiorix, and while his revolt had failed, the Gauls were finally realizing that Rome was here to stay. Setting aside generations of inter-tribal conflict, they began to unite against the invaders.

Vercingetorix realised that Roman discipline and organisation gave them the advantage on the battlefield, so he refused to engage them, instead opting for a scorched earth policy to deny the Romans supplies. Caesar hurried back from Italia, swiftly capturing the town of Avaricum. Having captured several other towns, Caesar then defeated a Gallic force at the Battle of Noviodunum. Realising that Caesar was marching to occupy the plateau of Gergovia, Vercingetorix shadowed his army across a river, destroying bridges they came across so he could attack the legions as they forded the river.

The extent of the Roman Republic in 40 BC after Caesar’s conquests

Caesar then deceived Vercingetorix by marching two thirds of his army in six units (looking like the full force), while the rest of his army rebuilt a bridge, which the legions could then cross. Realizing he had been duped, Vercingetorix now moved to race Caesar to Gergovia. 

Noting their insurmountable position, Caesar opted to attack the Gauls’ supply lines instead, and created a barricade to stop them being resupplied. The previously loyal Aedui were chosen to guard this supply line, but they now threw their lot in with Vercingetorix and attacked the Romans. Caesar took four legions and defeated the renegade Aedui, with his two legions maintaining the siege of Gergovia being hard pressed.

Caesar decided to lure Vercingetorix onto open ground for battle, taking several Gallic camps as they marched down. His legions did not realize his strategy, and due to the ease in taking these camps, assumed they were preparing for a general assault. They thus charged the Gauls and found themselves repulsed and exhausted. When a still-friendly force of Aedui arrived, they mistook them for enemies, and attacked their allies in the carnage. All Caesar could hope for now was to cover the retreat, though realizing the chaos unfolding, Vercingetorix led a cavalry charge which shattered the Roman lines. Gergovia went down as a rare defeat for Caesar.

Vercingetorix gave pursuit, though Caesar was able to link up with another of his armies following their northern campaign. Rather than sticking to his original plan of ignoring towns and waging a guerrilla war to oppose the Romans, Vercingetorix made the bizarre choice to make a stand at the town of Alesia. Given that he had 80,000 soldiers in the hilltop city, surrounded by two rivers, it seemed an insurmountable position. Vercingetorix sent out riders to summon his Gallic brothers to join him at the city and crush the Romans.

Caesar set to work besieging the city, building a ten-mile-long circumvallation (siege wall) to encompass the city, including 23 redoubts – an engineering marvel.

The Fortifications built by Caesar in Alesia according to the hypothesis of the location in Alise-Sainte-Reine. The circle shows the weakness in the north-western section of the contravallation line CC BY-SA 1.0

Imagine the feeling of despair for the Gauls inside the city as they watched the rapid construction of these siege works.

The Gauls harried Caesar with cavalry charges, though these were repulsed. Hearing of relief forces being summoned; Caesar had a defensive ditch built 500 meters away from his wall to prevent any sudden charges.

Archeodrome at Alise-Sainte Reine

Further ditches were dug, some submerged, some with sharpened stakes placed within, with the legionaries now foraging far and wide to find the supplies and the timber they needed.

CC BY-SA 3.0

The final part of Caesar’s epic siege works saw him build a contravallation, a second wall which now surrounded his legions, some 13 miles long.

Alesia now resembled a giant doughnut.

With the town in the center, then a no man’s land before the first wall, then the legions between that and the second wall, ahead of the arrival of the Gallic relief army.

Wanting to preserve their supplies, the Gallic council elected to expel their women and children from the city, assuming Caesar would give them safe passage. Caesar had other ideas though, and had no intention of allowing the Gallic civilians to leave when they could remain and further dwindle the city’s supplies, and made the brutal decision to refuse to allow them past the inner wall. The Gauls refused to allow them back into the city though, and instead were wailing as they were trapped in no man’s land between the Roman siege works and their own city. It must have been hugely demoralising for the Gallic soldiers within Alesia to have to watch their own wives and children dying from starvation and hunger while they were safe within.

A Gallic relief force, supposedly some quarter of a million strong, arrived and set up camp near the Roman fortifications. They managed to coordinate their attacks with the town against the inner and outer fortifications, but they were repulsed by the now-besieged legions. 

They attacked the following night but retreated when Mark Antony arrived with reinforcements in the morning. 

The Gauls saw a weak spot in the fortifications, a river passing through that the Romans could not build over, and a relative of Vercingetorix led 60,000 men to attack the vulnerability. Caesar had to dispatch his adjutants to defend various Gallic attacks on the wall, marching to the weak spots himself to rally the legionaries and repel the attacks. Caesar managed to get some of his auxiliary cavalry outside of the outer wall, and when he marched to engage the attack there, the Gauls looked like they were about to be surrounded, so fell back, only to be intercepted by the cavalry and slaughtered. They began to flee their camps, believing a huge Roman relief army to be arriving behind the cavalry, and only the exhaustion of his legion’s prevented a thorough rout by Caesar. 

The following day Vercingetorix met with the Gallic council and agreed to surrender himself to appease the Romans. Surrendering their weapons and chieftains, the war was over. 

Vercingetorix throws down his arms at the feet of Julius Caesar, painting by Lionel Royer

Alesia was a tactical masterclass by Caesar, and also a battle in which the difficulty of communication led to the Gaul’s defeat.

Had the Gauls within and outside the city been able to thoroughly coordinate their attacks, they likely would have overwhelmed the far smaller Roman force. It must have been hugely frustrating to have two huge armies yet lack the ability to coordinate attacks against the Romans who separated them, and thus blocked their communications.

Poster for the French film Vercingétorix by Cândido de Faria for Pathé, 1909. Collection EYE Film Institute Netherlands


The Battle of Alesia marked the end of the Gallic wars, with 50 BC spent conducting mopping up operations. The war had seen the Romans fighting three million Gauls, killing a third and enslaving a third, subjugating 300 tribes and destroying 800 cities. Gaul would remain pacified for centuries. The Senate declared 20 days of thanksgiving, though political friction in the city saw him denied a triumph. Vercingetorix was taken as captive by the Romans and would remain so for five years.

Gold stater of Vercingetorix, 53–52 BC.

Caesar’s star had reached its zenith, though despite his overwhelming public popularity, the Senate was becoming increasingly envious of him. As his proconsular imperium drew to a close, Pompey mobilized his supporters in Rome to make a stand against Caesar’s meteoric rise. Refusing to disband his own legions and seeing his supporters voice calls for Caesar to disarm, a clash between the two former triumvirs now looked inevitable.

Battle Of Alesia Written by Jack Tappin

Battle Of Alesia by Jack Tappin
Roman Empire