What was the Battle of Alesia (52 BC)?


The Battle of Alesia or Siege of Alesia was a military engagement in the Gallic Wars that took place in September, 52 BC, around the Gallic oppidum (fortified settlement) of Alesia, a major centre of the Mandubii tribe. It was fought by the army of Julius Caesar against a confederation of Gallic tribes united under the leadership of Vercingetorix of the Arverni. It was the last major engagement between Gauls and Romans, and is considered one of Caesar’s greatest military achievements and a classic example of siege warfare and investment. The battle of Alesia marked the end of Gallic independence in France and Belgium.

The battle site was probably atop Mont Auxois, above modern Alise-Sainte-Reine in France, but this location, some have argued, does not fit Caesar’s description of the battle. A number of alternatives have been proposed over time, among which only Chaux-des-Crotenay (in Jura in modern France) remains a challenger today.

At one point in the battle the Romans were outnumbered by the Gauls by four to one. The event is described by several contemporary authors, including Caesar himself in his Commentarii de Bello Gallico. After the Roman victory, Gaul (very roughly modern France) was subdued and became a Roman province. The Roman Senate granted Caesar a thanksgiving of 20 days for his victory in the Gallic War.


In 58 BC, following his first consulship in 59 BC, Julius Caesar engineered his own appointment as proconsul (governor) of three Roman provinces by the First Triumvirate. These were Cisalpine Gaul (northern Italy), Illyricum (on the eastern coast of the Adriatic Sea) and Gallia Narbonensis (in southeastern France and the rest of France’s Mediterranean coast). Although the proconsular term of office was meant to be one year, Caesar’s governorship was for an unprecedented five years. He also had the command of four legions.

Caesar engaged in the Gallic Wars (58-50 BC), which led to his conquest of Gaul beyond Gallia Narbonensis. When the Helvetii, a federation of tribes from what is now Switzerland, planned a migration to the Atlantic coast through Gaul, Caesar went to Geneva and forbade the Helvetii to move into Gaul. While he went to Gallia Cisalpina to collect three other legions, the Helvetii attacked the territories of the Aedui, Ambarri, and Allobroges, three Gallic tribes, which called for Caesar’s help. Caesar and his Gallic allies defeated the Helvetii. The Gallic tribes then asked for Caesar to intervene against an invasion by the Suebi, a Germanic tribe. Caesar defeated the Suebi. In 57 BC he intervened in intra-Gallic conflicts and marched on the Belgae of northern Gaul. From then on he conquered the Gallic peoples one by one. His successes in Gaul brought Caesar political prestige in Rome and great wealth through the spoils of wars and the sale of war captives as slaves.

After his initial successes, Caesar had to confront a number of Gallic rebellions which threatened his control over Gaul.

In the winter of 54-53 BC the Carnutes (who lived between the rivers Seine and Loire in central France) killed Tasgetius, a pro-Roman king who had been installed by Caesar. Caesar sent one legion to winter there. Soon after the previously pacified Eburones (who lived in the Ardennes region of Belgium and part of northern France), commanded by Ambiorix, rebelled and destroyed the Legio XIV under the command of Quintus Titurius Sabinus in a carefully planned ambush. This was the first clear Roman defeat in Gaul and inspired widespread national sentiments and rebellion. The Eburones obtained the support of the Atuatuci (from eastern Belgium), the Nervii (from central Belgium) and numerous minor tribes. They besieged the camp of Quintus Cicero. The siege lasted two weeks. Cicero managed to inform Caesar about this by sending a Nervian noble to him with a letter. This siege was difficult for Cicero because the Gauls had learnt Roman siege techniques and built siege machines similar to those of the Romans. Caesar undertook a forced march from Samarobriva (Amiens, in northern France) with two legions and defeated the besiegers. He made Samarobriva his headquarters. However, the Senones (who lived in an area of the River Seine in northern France) rebelled and were supported by many Gallic tribes. Only the Aedui and Remi remained loyal to Rome. Moreover, the Treveri (from north-eastern Gaul) attacked the legate Titus Labienus, who managed to defeat them, killing their leader.

Caesar levied two more legions and received another from Pompey. This brought the number of his legions in Gaul to ten. The Treveri obtained the support of the Eburones, Nervii and Atuatuci. On the western front, the Senones, the Carnutes and other nearby peoples continued their rebellion. Caesar made a lightning move on the Nervii, ravaging their fields and seizing a large amount of cattle. The Nervii, caught by surprise, surrendered. Caesar then turned west against the Senones and Carnutes. They negotiated for peace with the mediation of the Aedui and the Remi. Only Acco, a seditious prince, was chained. He was later executed as a warning to Gaul. Caesar then turned against the Treveri, the Eburones and their allies. He marched on the Menapi with five legions without baggage. The Menapi hid in the forests. Caesar split his army into three columns and burned many villages and seized much of the cattle. The Menapi surrendered. Meanwhile, Labienus quickly moved on the Treveri with 25 cohorts and the cavalry and without baggage. He defeated them by a river in Belgium and installed a pro-Roman leader. After a second punitive expedition in Germania, Caesar turned his whole army on the Eburones and Ambiorix and sent his cavalry ahead for a surprise attack. The Eburones fled to the forests. Minor nearby tribes sued for peace. Caesar divided nine legions into three columns. One was to control the Menapi, one was to devastate the territories next to the lands of the Atautuci and his pursued Ambiorix.

He decided to annihilate the Eburones. Since it was difficult to find them in the forest and the marshes where they hid, he got the Gallic tribes in the region to do this. Villages and farms were burnt, the cattle were killed and all the grain was taken. The survivors starved. Caesar went to Durocortorum (Reims, in north-eastern France) among the Remi. He stationed two legions at the border with the Treviri, two in the land of the Lingones and six among the Senones. He then returned to northern Italy.

Prelude to the Battle

Caesar’s hard-won and ruthless campaigns were not the end of Gallic unrest. The Carnuti gathered at Cenabum (modern Orléans) and killed all the Romans who lived there. The news quickly spread around Gaul. Vercingetorix called for a rebellion by his Arverni of the Auvergne region of central Gaul. However, some tribal chiefs opposed this and expelled him from Gergovia (Gergovie, in south central Gaul), the capital. Vercingetorix gathered support in the countryside, overthrew them and proclaimed himself king. He sent messages to the nearby peoples in search for support against the Romans. He managed to enlist the Senones, the Parisii from around the River Seine, the Pictones from the Bay of Biscay, the Cadurci from south-western Gaul, the Turones from the area of Tours, the Aulerci from Armorica, an area between the Seine and Loire rivers which included Brittany, the Lemovices from Limousin and Poitou, the Andecavi from Angers on the River Loire, and all the tribes on the coast of the Atlantic. Vercingetorix quickly gathered a large army, sent some troops under Lucterius, the leader of the Cadurci, to the land of the Ruteni (in Aveyron, southern Gaul) and went to the land of the Bituriges (in the Bourges area, central France). Lucterius enlisted three tribes in southern Gaul: the Ruteni, the Nitiobrogi of Agenais (Perigot) and the Gabali of Aquitania.

Caesar hurried to Gallia Narbonensis and placed garrisons among the Ruteni, the Volci Arecomici, the Tolosates of Toulouse and around the capital, Narbo (Narbonne). Lucterius withdrew and Caesar pursued him. This forced Vercingetorix to return to the territory of his Arverni. Caesar foresaw this and undertook a forced march to the land of the Lingones, where two legions had been wintering. He then marched with eight legions and seized Vellaunodunum (which belonged to the Senones), Cenabum (the Capital of the Carnuti) and Noviodunum (modern Nouan-le-Fuzelier), which belonged to the Bitiriges. He then seized Avaricum, the largest town of the Bituriges. The town fell after 27 days and 40,000 inhabitants were slaughtered. Even though Vercingetorix had a larger army, he avoided open battle. After the winter, Caesar sent Titus Labienus north to suppress a revolt by the Senones and the Parisii with four legions. He marched on Gergovia along the River Elaver (the River Allier, in central France) with six legions. Vercingetorix destroyed all the bridges. The Aedui, who were longstanding Roman allies, at this time sided with the Gallic leader and Caesar temporarily withdrew to deal with them. He then made for Gergovia, where he was defeated before the city walls. Two days later he prepared for a pitched battle, but Vercingetorix declined. The Aedui rebelled again, killing all the Romans in their area and placing garrisons along the River Loire. Caesar was left with only the Lingones and Remi as allies. Meanwhile, Labienus managed to defeat a coalition of peoples north of the River Loire and rejoined Caesar, escaping attempts to encircle him first by the Bellovaci, who also rebelled, and then the Aedui.

A general council was summoned at Bibracte (Autun, in Burgundy), the capital of the Aedui, once the supporters of Caesar, but now against him. The Treveri, Remi and Lingones (the only two Roman allies left since the defection of the Gallic majority) did not take part. The council declared Vercingetorix commander of the united Gallic armies. He ordered hostages from all the convened Gallic peoples and the gathering of 15,000 cavalry. He deemed the infantry he had sufficient. He would not accept a pitched battle. The cavalry would destroy the Roman supplies of grain and hay and the Gauls would have to destroy their own grain and burn their houses. He sent 10,000 infantry and 800 cavalry of the Aedui against the Allobroges in the Roman province, the Arverni and the Gabali (a tribe of Aquitania) against the Helvii, and the Ruteni and Cadurci to devastate the territory of the Volcae Arecomici. However, these were met by the Roman garrisons which had 22 cohorts.

After being reinforced by Labienus and the four legions who had been campaigning in the Seine area, Caesar went to the Lingones. He strengthened his army with Germanic mercenary cavalry units and headed for Gallia Narbonensis. He was attacked by Vercingetorix north-west of Dijon, in eastern Gaul. The attack was repelled by the Roman legions and the Germanic cavalry. The confidence of the rebels was shaken and Vercingetorix decided to withdraw to Alesia, the capital of the Mandubii. Caesar then besieged Vercingetorix in Alesia.

The Siege

Alesia was an oppidum (fortified settlement) on a lofty hill, with two rivers on two different sides. Due to such strong defensive features, Caesar decided on a siege to force surrender by starvation. Considering that about 80,000 men were garrisoned in Alesia, together with the local civilian population, this would not have taken long. To guarantee a perfect blockade, Caesar ordered the construction of an encircling set of fortifications, a circumvallation, around Alesia. It was eleven Roman miles long (16 km or 10 modern miles), each Roman mile equal to 1,000 paces and had 23 redoubts (towers). While work was in progress, the Gauls carried out cavalry sallies to disrupt the construction. Caesar placed the legions in front of the camp in case of a sortie by the enemy infantry and got his Germanic allies to pursue the Gallic cavalry.

Vercingetorix sent messengers around Gaul to rally the tribes to war and come to Alesia. When Caesar heard of this from deserters and captives, he dug a trench twenty pedes (6 metres, 19 modern feet) with perpendicular sides and built all the other works four hundred stades (probably 592 m, 1943 feet) away from that trench. The object of placing this trench so far away from the rest of the works was, as Caesar explained, that the manning of the entrenchment was not easy and, thus, this distance was a protection against surprise enemy advances at night or against javelins or other missiles being thrown at the Roman troops which were building the works during the day. Between this advance trench and the entrenchment, he dug two more trenches 15 pedes (4.45 m, 14.6 ft) wide and deep. He filled the inner one, where the ground was level with the plain or sank below it, with water from the river. Behind the three trenches he built a rampart riveted with palisades 12 pedes high (3.57 m, 11.7 ft). On top this he built battlements (parapets with squared openings for shooting through) and breastwork (wooden screens at breast height to protect the defenders) with large horizontal pointed stakes projecting from the joints of the screens to prevent the enemy from scaling it. All round the works he set turrets at intervals of 80 pedes (24 m, 78 ft).

Some of the Roman soldiers had to go a considerable distance to get the timber for the construction of the works and grain to feed the troops. This reduced the number of troops at the Roman works. The Gauls made sorties with large forces to attack the works. Therefore, Caesar added further structures to the works to make them defensible by the reduced number of troops. Cut tree trunks were sharpened to create stakes. They were fastened at the bottom and sunk into a five pedes deep trench (1.5 m, 4.9 ft) with the boughs protruding from the ground. They were tied in rows of five so that they could not be pulled up without being impaled by the sharp stakes. Pits three pedes (0.9 m, 2.9 ft) deep which sloped inwards slightly to the bottom were dug in front of the stakes. They were placed in five intersected rows in the shape of a quincunx (an arrangement of five objects with four at the corners and the fifth at the centre). Tapering stakes, the thickness of a man’s thigh, were sharpened at the top, hardened with fire, and sunk in the pits. They protruded from the bottom of the pit to a height of four fingers. Earth was pressed hard to a height of one foot from the bottom of the pit to make the stakes firm. The rest of the pit was covered with twigs and broken-off tree branches to hide the trap. Eight rows of this kind were placed three pedes (0.9 m, 2.9 ft). In front of these, one pes (0.3 m, 0.97 ft) stakes with iron hooks were sunk into the ground and scattered close to each other all over the field.

To prepare for the arrival of the Gallic relief forces, Caesar constructed an outer fortification (a contravallation) with the same specifications but facing the opposite way as protection against the external attack by this relief force. It followed the most favourable ground and formed a circuit of 14 Roman miles (20.7 km, 12.86 modern miles). The besiegers were preparing to be besieged.

The food supply of the population of Alesia and the 80,000 soldiers it hosted could not last long. Vercingetorix ordered all the grain to be brought to him and rationed it. The Gauls held a council, and it was decided that the old and the sick should leave the town. The inhabitants of the town also sent out their wives and children to save food for the fighters, hoping that Caesar would take them as captives and feed them. However, Caesar forbade their being admitted to his fortification, and instead left them to starve to death.

The Battle

Meanwhile, the Gallic relief force arrived and encamped on a hill one mile from the Roman fortification. The next day the Gauls encamped near the town. They then attacked the outer Roman fortification. The besieged Gauls simultaneously attacked the inner Roman fortification. However, this combined attack was unsuccessful. The next day the Gauls attacked at night. Marc Antony and Caius Trebonius brought in troops from the remotest forts in support of their comrades. At the first light of day, the Gallic relief forces, fearing being surrounded by a Roman sally, withdrew. The advance of the besieged Gauls, led by Vercingetorix, was delayed by having to fill trenches dug by the Romans. On hearing of the retreat of their comrades the besieged Gauls returned to the town.

The Gauls spotted a weakness in the Roman fortification. The north side of a hill could not be included in the Roman works and they placed a camp with two legions on steep and disadvantageous ground (this is indicated by a circle in the figure). Thus, the Gauls selected 60,000 men and appointed Vercassivellaunus, a near relative of Vercingetorix, to lead the attack on that spot. They marched there before dawn and launched the attack at noon. Vercingetorix made a sally and attacked any part of the inner fortification which seemed weak. Caesar sent Labienus to support the defense of the weak area with six cohorts of cavalry. He sent Brutus with six cohorts of cavalry and then Caius Fabius with a further seven cohorts of cavalry to defend the inner fortification. Finally, leading fresh troops, he joined in. The attack was repelled.

Caesar then marched to the assistance of Labienus, drafting four cohorts and ordering part of the cavalry to follow him and part of it to leave the outer fortification and attack the Gallic relief force from the rear. Labienus was on the verge of collapse and informed Caesar of his decision of making a sally as he had been instructed. Caesar hastened. His arrival galvanised the Roman troops, who “lay aside their javelins [and] carr[ied] on the engagement with their swords.” The Roman cavalry was suddenly seen at the rear of the Gauls, the Roman troops advanced rapidly and the Gauls fled. They were intercepted by the cavalry and slaughtered. The besieged Gauls were pulled back from the fortification. They fled their camps and Caesar commented that “had not the soldiers been wearied by sending frequent reinforcements, and the labour of the entire day, all the enemy’s forces could have been destroyed”. At midnight the Roman cavalry was sent to pursue them. Many were killed and many fled to the lands they came from.

The next day Vercingetorix convened the Gallic council and proposed that he should be killed or surrendered alive to appease the Romans. Caesar ordered the Gauls to surrender their weapons and deliver their chieftains. The chieftains were brought before him and Vercingetorix was surrendered. Captives were given to the Roman soldiers as part of the spoils of war apart from the Aedui and Arverni, whom he hoped to win over.

Aftermath and Legacy

Alesia proved to be the end of generalized and organized resistance against Caesar’s invasion of Gaul and effectively marked the end of the Gallic Wars. In the next year (50 BC) there were mopping-up operations. During the Roman civil wars Gallia was essentially left on its own. Marcus Vipsanius Agrippa became its first governor in 39-38 BC. In 39 BC he settled the Ubians on the west bank of the River Rhine and in 38 BC he suppressed a rebellion in Aquitania. He built a radial network of roads centred on the Gallic capital, Lugdunum (Lyon). Gallia was divided into three Roman provinces; Gallia Aquitania, Gallia Lugdununensis and Gallia Belgica. Only the Arverni kept their independence thanks to their victory against Caesar at the Battle of Gergovia.

For Caesar, Alesia was an enormous personal success, both militarily and politically. The senate declared 20 days of thanksgiving for this victory but, due to political reasons, refused Caesar the honour of celebrating a triumphal parade, the peak of any general’s career. Political tension increased, and two years later, in 49 BC, Caesar crossed the Rubicon, precipitating the Roman Civil War of 49-45 BC, which he won. After having been elected consul for each of the years of the civil war, and appointed to several temporary dictatorships, he was finally made dictator perpetuus (dictator for life), by the Roman Senate in 44 BC. His ever-increasing personal power and honours undermined the tradition-bound republican foundations of Rome. More civil wars followed his assassination. The last one was a conflict between Octavian (later known as Augustus) and Marc Antony over who would be the sole ruler of Rome. Octavian won. This led to the end of the Roman Republic and the beginning of rule by emperors.

Caesar’s commanders followed different paths. Labienus sided with the Optimates, the conservative aristocratic faction Caesar fought against in his civil war, and was killed at the Battle of Munda in 45 BC. Caius Trebonius, one of Caesar’s most trusted lieutenants, was appointed consul by Caesar in 45 BC, and was one of the senators involved in Caesar’s assassination on the Ides of March (March 15), 44 BC. He was himself murdered a year later. Caius Fabius held up the Pompeian forces at Ilerda until Caesar got there and won the Battle of Ilerda in 49 BC. Decimus Junius Brutus Albinus was entrusted with fleet operations by Caesar during his civil war. He was put in charge of the naval blockade of Massilia (Marseilles) during the Siege of Massilia by Caesar’s forces. He built a fleet from scratch and secured the capitulation of the city. He, too, joined the conspiracy to assassinate Caesar. Marc Antony continued to be a faithful supporter of Caesar. He was made Caesar’s second in command, as Master of the Horse, in 47 BC during Caesar’s second dictatorship and was left in charge in Italy. He mishandled a political issue and deployed troops against a crowd in Rome. Caesar stripped him of his office. He received no appointments in 46 BC and 45 BC. In 44 BC he was elected as Caesar’s consular colleague. After Caesar’s murder, Antony was part of the Second Triumvirate, an alliance with two other Caesarians, Octavian and Lepidus. Marc Antony and Octavian defeated the forces of the assassins of Caesar in the Liberators’ civil war. Later Octavian declared war on Cleopatra VII of Egypt in order to fight Marc Antony, her ally and lover. They were defeated at the Battle of Actium in 31 BC. They went back to Egypt. Marc Antony was defeated again and the two committed suicide.

Vercingetorix was taken prisoner and held as a captive in Rome for the next five years awaiting Caesar’s triumph. As was traditional for such captured enemy leaders, he was paraded in the triumph, then taken to the Tullianum and ritually garrotted.


Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.