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Battle of Alesia (52 BCE) was further evidence that Julius Caesar was an outstanding commander. In Alesia, he had to face the simultaneous attacks of the besieged troops of Vercingetorix and the army of Gauls, coming to their rescue. The actions of the legions near Alesia constitute the largest siege operation in antiquity.
Background of events
A Roman leader Gaius Julius Caesar, as proconsul of Cisalpine Gaul in 58-51 BCE conquered all of Gaul all the way to the English Channel and the Atlantic Ocean. Meanwhile, he also made an attempt to conquer Britain and the lands beyond the Rhine, which resulted in the Romans having less power in Gaul itself. The ambitious Gallic chiefs tried to take advantage of the situation, trying to unite the conflicted barbarian tribes. The first attempts were unsuccessful, but in early 52 BCE the young prince of Arverni – Vercingetorix finally joined forces. Using scorched earth tactics, he had some success, temporarily cutting off even Caesar’s main force in Pre-Alpine Gaul.
Uprising outbreak
The leader of the allied Gallic tribes raised the insurrection to drive the Romans out of Gaul. For this purpose, a huge crowd of soldiers was called up, almost 200,000 warriors. The young commander forced/encouraged other tribes to revolt, except the Aedui allied with Rome and other lesser tribes. Julius Caesar upon learning of the rebellion, he immediately set off to the various camps scattered throughout Gaul to assemble an army. With a smaller but more experienced army at his disposal, he was able to react faster to any threats. He was aware that this trip would be longer, so he needed more supplies as well. The allied tribes did not send him food, either for fear of Vercgetorix or for lack of it.
Caesar began his campaign by capturing small towns and seizing supplies. After a streak of small victories, there was a shortage of grain and food. Caesar, discouraged, began the siege of Avaricum. After a long siege, he captured the city and plundered it completely. The Gallic chieftain, Vercingetorix, “sat on the tail” of Caesar the whole time, attacking his rearguard with his cavalry.
After the fall of Avaricum, Caesar directed his troops to the hill of Gergovia. The city, however, after long battles, repelled the Roman army and forced them to retreat. Caesar, attacked from the rear at the same time by the Edu (who had gone over to the Gauls), had to join Titus Labienus – commander of some of his troops in the fighting in the east. Labienus had a reputation for being a very good commander who (later) betrayed Caesar and went over to Pompey in the Civil War.
After joining forces and recruiting new troops, Caesar headed east against the Sequans and the Lingons. Vercingetorix, wishing to destroy the Roman army, set a trap during the march, which, unfortunately, was not successful for him. Caesar’s troops repelled his rival and forced him to retreat. A discouraged Gallic commander retreated to Alesia(today’s Auxois hill – about 30 kilometers west of today’s Dijon) to rest there and renew the army. However, he did not expect Caesar to follow the army of Gauls and surround his forces in the city. This was how the long blockade of Alesia was to begin.
Armies
Roman army amounted to nearly 60,000 soldiers (12 legions with cavalry and auxiliaries). When it comes to riding, it could have been from 1,000 to 1,500 horsemen, as Caesar recruited an additional unit of 500 Germanic horses in Germania.
The Gallic army was around 80,000 soldiers under the personal command of Vercingetorix and 120-250,000 in support. The cavalry of the Gauls was larger in numbers and could have amounted to about 4,000. According to Plutarch’s data, the support forces could be as high as 300,000 people. According to modern data, they could be around 100,000.
Siege
The fortress of Alesia was situated on a high hill in the fork of the Lutosa and Osera rivers, practically inaccessible to the advancing troops. Therefore, Caesar decided on a long-lasting siege and forcing the defenders to surrender through starvation. This is how Caesar himself describes the fortress and fortifications of the Romans:
The actual stronghold of Alesia was set atop of a hill, in a very lofty situation, apparently impregnable save by blockade. The bases of the hill were washed on two separate sides by rivers. Before the town a plain extended for a length of about three miles; on all the other sides there were hills surrounding the town at a short distance, and equal to it in height. Under the wall, on the side which looked eastward, the forces of the Gauls had entirely occupied all this intervening space, and had made in front a ditch and a rough wall six feet high. The perimeter of the siege-works which the Romans were beginning had a length of eleven miles. Camps had been pitched at convenient spots, and three-and‑twenty forts had been constructed on the line. In these piquets would be posted by day to prevent any sudden sortie; by night the same stations were held by sentries a