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Vercingetorix's Revolt was the last of the Gallic Wars and the end of Gaius Julius Caesar's attempt to conquer Gaul. This war also established the Arverni as the nominal controllers of Gaul, and established their leader, Vercingetorix, as the first High King of Gaul.
Julius Caesar, under the banner of the Roman Republic, had since 58 BC invaded Gaul in force, allowing Roman citizens to settle and pacifying the many tribes. Gallic life has been quite disrupted by Caesar's invasion. The Romans allowed no migrations to take place, meaning that the Gauls were forced for the first time in their history to absolutely remain in their territories and deal with whatever problems that arose, namely raids by the Germanic tribes and internal power struggles. This thoroughly alienated the Gauls from the Romans, and in their mutual foe they began to develop national bonds between the tribes, based on their Celtic heritage.
Caesar was forced to return to Gaul and deal with rebellion in 54 BC. This action gave the Gauls a personal, common enemy. In this charged political climate, the king of the Arverni, Vercintegorix, began to gather the tribes and unite them to destroy the Roman threat. Vercingetorix's natural charisma led him to become the nominal overlord of the various Gallic tribes, and the only man who could contest his reign over Gaul was Julius Caesar.
The begining of the revolt against Julius Caesar was begun by the Carnutes tribe in early 52 BC. Led by their leaders Cotuatus and Conetodunus, the Carnutes rose en masse and slaughtered Roman settlers within their territory. The revolt launched at this time because it was believed that Caesar would be distracted by the political turmoil in Rome caused by the death of Publius Clodius Pulcher. Caesar's lack of definite response encouraged other tribes to revolt.
Vercingetorix, a young nobleman of the Arvernian city of Gergovia, roused his dependents to join the revolt, but he and his followers were expelled by the nobles of the city, including Vercingetorix's uncle Gobanitio, because they thought opposing Caesar was too great a risk. Undeterred, Vercingetorix raised an army of the poor, took Gergovia and was hailed as king. He made alliances with other tribes, and having been unanimously given supreme command of their armies, imposed his authority through harsh discipline and the taking of hostages. He adopted the policy of retreating to natural fortifications, and undertook an early example of a scorched earth strategy by burning towns to prevent Caesar's forces from living off the land.
Battle of Avaricum
Vercingetorix won some initial skirmishes with the Roman Legions led by Caesar and his lieutenant Titus Labienus. However, he did not manage to damage the Roman Legions enough to deter Caesar from attacking the capital of the Bituriges, Avaricum. The city fell under siege by Caesar's troops for a full two months, reducing Caesar's food supply by a significant percentage. Avaricum's fortification were almost entirely destroyed by Caesar's forces. Total victory would have followed, with the city's population being put to the sword and its stores seized by Caesar's troops, if a large Gallic army, led by Cotuatus, diverted the Romans, who feared leaving themselves vulnerable to attack from the rear, long enough for the city to be mostly abandoned and its stores put to the torch. Caesar, well aware of the possibility of his forces starving, retreated from the city after slaughtering the remaining inhabitants. However, his forces resupplied by besieging the town of Noviodunum. Vercingetorix attempted to force Caesar from Noviodunum, but his forces were defeated in the battle.
Battle of Gergovia
Although Vercingetorix had been forced by Roman maneuvers to abandon the city of Gergovia to the Romans in late 52 BC, in Winter 51 BC his forces attacked and retook the city while Caesar was gathering his forces to strike at the Gauls. This left Caesar in a difficult position; he was forced to choose between keeping his forces safe over the winter but showing weakness to the remaining allies of Rome in the area, or attacking the Gauls on the open plain and risk running out of supplies. Caesar chose the latter.
With the winter almost over, Caesar went in person to regain Aedui support, and then detached a force of four legions under Titus Labienus to advance into Senones and Parisii territory, taking the remaining 6 legions, Aedui auxilliaries and Germanic cavalry to Gergovia himself. In response, Vercingetorix broke down all the bridges over the river Allier and began to march along its opposite bank. This did not prevent Caesar from crossing, but Vercingetorix continued to advance his force faster than Caesar's, so that the choice of when and where to give battle remained his.
Five days later Caesar reached Gergovia and, realising its mountainous location made a frontal assault risky, relied on his superior siege tactics. He ordered a double trench, 12 feet wide, to be constructed between a captured hill and his main camp. Intending to completely encircle Gergovia and starve the Gauls inside, Caesar was interrupted by betrayal from his Gallic allies the Aedui, led by Litaviccus whom he fought and defeated after a desperate struggle.
Caesar then went back to Gergovia and realised that his siege would fail. His only chance now of victory was to get Vercingetorix off the high ground. He used a legion as a decoy and moved onto better ground, capturing three Gallic camps in the process. He then ordered a general retreat to fool Vercingetorix and pull him off the high ground. However, the retreat was not heard by most of Caesar's force. Instead, spurred on by the ease with which they captured the camps, they pressed on toward the town and mounted a direct assault on it. The noise of the assault drew Vercingetorix back into the town. Forty-six centurions and 700 legionaries died in the resulting engagement, and over 6,000 were wounded on the Roman side, compared to the several hundred Gauls killed and wounded. In the wake of the battle, Caesar lifted his siege and advanced instead into Aedui territory.
Battle of Alesia
Vercingetorix, despite his victories, believed that the time was not right for another battle and regrouped his forces in Alesia. Several skirmishes between cavalry resulted in the Roman army surrounding the fortress.
Alesia was a hill-top fort surrounded by river valleys, with strong defensive features. As a frontal assault would have been hopeless, Caesar decided upon a siege, hoping 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, called a circumvallation, around Alesia. The details of this engineering work are known from Caesar's Commentaries. About 18 km of four metre high fortifications were constructed in about three weeks. This line was followed inwards by two four-and-a-half metre wide ditches, also four-and-a-half metres deep. The one nearest to the fortification was filled with water from the surrounding rivers.These fortifications were supplemented with mantraps and deep holes in front of the ditches, and regularly spaced watch towers equipped with Roman artillery.
Vercingetorix's cavalry often raided the construction works attempting to prevent full enclosure. The Roman auxiliary cavalry proved its value and kept the raiders at bay. After about two weeks of work, a detachment of Gallic cavalry managed to escape through an unfinished section. Anticipating that a relief force would now be sent, Caesar ordered the construction of a second line of fortifications, the contravallation, facing outward and encircling his army between it and the first set of walls. The second line was identical to the first in design and extended for 21 km, including four cavalry camps. This set of fortifications would protect the Roman army when the relief Gallic forces arrived: they were now besiegers and preparing to be besieged.
At this time, the living conditions in Alesia were becoming increasingly worse. With 80,000 soldiers and the local population, too many people were crowded inside the plateau competing for too little food. The Mandubii decided to expel the women and children from the citadel, hoping to save food for the fighters and hoping that Caesar would open a breach to let them go. This would also be an opportunity for breaching the Roman lines. But Caesar issued orders that nothing should be done for these civilians and the women and children were left to starve in the no man's land between the city walls and the circumvallation. The cruel fate of their kin added to the general loss of morale inside the walls. Vercingetorix was fighting to keep spirits high, but faced the threat of surrender by some of his men. However, the relief force arrived in this desperate hour, strengthening the resolve of the besieged to resist and fight another day.
At the end of September the Gauls, commanded by Commius, attacked Caesar's contravallation wall. Vercingetorix ordered a simultaneous attack from the inside. None of the attempts were successful and by sunset the fighting had ended. On the next day, the Gallic attack was under the cover of night. This time they met more success and Caesar was forced to abandon some sections of his fortification lines. Only the swift response of the cavalry commanded by Antony and Gaius Trebonius saved the situation. The inner wall was also attacked, but the presence of trenches, which Vercingetorix's men had to fill, delayed them enough to prevent surprise. By this time, the condition of the Roman army was also poor. Themselves besieged, food had started to be rationed and the men were near physical exhaustion.
On the next day, October 2, Vercassivellaunus, a cousin of Vercingetorix, launched a massive attack with 60,000 men, focusing on a weakness in the Roman fortifications (the circle in the figure) which Caesar had tried to hide, but had been discovered by the Gauls. The area in question was a zone with natural obstructions where a continuous wall could not be constructed. The attack was made in combination with Vercingetorix's forces who pressed from every angle of the inner fortification. Caesar trusted the discipline and courage of his men and sent out orders to simply hold the lines. He personally rode throughout the perimeter cheering his legionaries. Labienus' cavalry was sent to support the defense of the area where the fortification breach was located. With pressure increasing, Caesar was forced to counter-attack the inner offensive and managed to push back Vercingetorix's men. By this time the section held by Labienus was on the verge of collapse. When this section fell, Vercingetorix led the entirety of his army into the gap. Caesar's exhausted legionaries attempted to prevent the escape, and in the process were slaughtered by the extremely motivated and well-supplied Gauls.
Caesar had lost the majority of his legions to Vercingetorix's revolt. In addition to this, Vercingetorix's revolt showed that the Romans could be beaten; and amplified the already present organized resistance to the Roman invasion. The Romans would shortly be pushed entirely from their Gallic possessions, excepting those in the south.
Vercingetorix was declared the first High King of Gaul, and united all the Celtic tribes of Gaul. The Gauls learned much from Romans remaining on their land and defecting Roman legionaries, which revolutionized their military tactics. Gaul now was practically Rome's equal on the field, and the Republic was forced to keep formal relations with it.
Caesar was recalled to Rome, where he engaged in a civil war. He never returned to Gaul, leaving his conquest incomplete.