Vercassivellaunus, kinsman to Vercingetorix, has been given the task of ripping a hole through Caesar’s defences once and for all. The previous two assaults had come to nothing but a bloody mess, so this time a careful reconnaissance was conducted by scouts led by local farmers who probed the Roman lines, searching for that one spot that was most susceptible to a concentrated strike. On the north-western stretch of the circumvallation one camp had been established on the lower slopes of the high ground that anchored that sector, a decision that would give Vercassivellaunus his chance. Having assembled the best warriors from among the besieging Gallic army’s tribes, the force (numbering many thousands) marched around the northern flank of the Roman position on the hill, appearing on the high ground in front of the camp. As the Gauls broke from cover and began their advance they showered the Romans manning the watchtowers with arrows and javelins, the high ground giving them an advantage in range. Proving that the Romans were not the only ones who could learn from their enemies, the columns of Gauls assembled into dense testudo formations, interlocking their shields in front, at the sides and over their heads, creating a mass of men virtually invulnerable to the Roman archers and slingers (if not the artillerists) positioned on the earthen ramparts. Using this new tactical formation, the Gauls slowly covered the ground to the wall, neutralizing all the Roman defences as they went. By the time afternoon reached its height the vanguards of the Gallic columns had ground their way into the very teeth of the Roman rampart – a potentially fatal dagger-thrust through Caesar’s line that had to be stopped at all costs.
The Gallic Relief Army
The Gallic relief army, meanwhile, had finally arrived. Led by its four chieftains it quickly established itself on a south-western hill less than 1.5km from the Roman fortifications. The following day it arrayed itself for battle on the western plain, with its ranks of cavalry in the vanguard and the vast swathes of its infantry positioned further back on higher ground. The imposing sight caused immediate celebration in Alesia, with the defenders rushing forth in battle array, carrying fascines that, together with loose earth, they used to fill in the Roman ditch in anticipation of rushing across it into battle. With the gauntlet thrown down, the Romans went into action: ‘Caesar disposed the whole army on both faces of the entrenchments in such fashion that, if occasion should arise, each man could know and keep his proper station; then he ordered the cavalry to be brought out of camp and to engage’ (Caesar, CBG 7.80).
As the two cavalry forces moved against each other the Romans were surprised to find that the Gauls had seeded the ranks of their horsemen with archers and light infantry to give them cover in the event that the cavalry had to retreat, but also to help break up any Roman charges. The tactic bore fruit, with numbers of Caesar’s Germanic horsemen withdrawing from the battle wounded, resulting in thunderous cheers from the Gallic spectators on both sides of the walls. Caesar recounted how
As the action was proceeding in sight of all, and no deed, of honour or dishonour, could escape notice, both sides were stirred to courage by desire of praise and fear of disgrace. The fight lasted, and the victory was doubtful, from noon almost to sunset; then the Germans in one part of the field massed their troops of horse, charged the enemy and routed them, and when they had been put to flight the archers were surrounded and slain. Likewise, from the other parts of the field, our troops pursued the retreating enemy right up to their camp, giving them no chance of rallying. (Caesar, CBG 7.80)
The heaving ranks of Gauls that stood by the Roman trench and lined the slopes of Alesia were utterly downcast by a defeat they did not expect and which, despite having seemed so close, turned out to be an unequivocal Roman victory. They retreated back behind the walls of their oppidum, dispirited.
After a day of rest the Gauls made another attempt at midnight, advancing silently under cover of darkness towards the Roman fortifications on the western plain. They had equipped themselves with great numbers of hurdles, ladders and grappling hooks, and announcing their arrival to those besieged behind the walls with a great war cry, the Gauls leapt forward. The great number of their missile weapons gave them an initial advantage, but this dwindled as they came closer to the fortifications, Cassius Dio recording how
they tried to enter the city by night through the wall of circumvallation, but met with dire disaster; for the Romans had dug secret pits in the places which were passable for horses and had fixed stakes in them, afterward making the whole resemble on the surface the surrounding ground; thus horse and man, falling into them absolutely without warning, came to grief. (Cassius Dio, Roman History 11.40)
The weight of the attack seems, however, to have driven it through the lilia and cippi, with the hurdles and scaling equipment employed against the outer wall, while a concurrent assault was reaching the same section of the inner wall, launched by Vercingetorix as soon as he heard the great shout raised by Vercassivellaunus’s relieving Gauls.
Caesar noted that ‘Our troops, as on previous days, moved each to his appointed station in the entrenchments; with slings, one-pounders [light ballistae], stakes set ready inside the works, and bullets, they beat off the Gauls. As the darkness made it impossible to see far, many wounds were received on both sides’ (Caesar, CBG 7.81). The commanders responsible for that section of the defences, Marcus Antonius and Gaius Trebonius, drew reinforcements from forts and sent them in to bolster hard-pressed areas, thus ensuring that the integrity of both the inner and outer walls was maintained. Many Gauls fell victim to Roman booby traps, as well as from scorpio bolts and other missiles launched from the rampart and watchtower turrets. The Gauls ‘perished on every side. Many a man was wounded, but the entrenchment was nowhere penetrated; and when daybreak drew nigh, fearing that they might be surrounded on their exposed flank by a sortie from the camps above them, they retired to their comrades’ (Caesar, CBG 7.82). Vercingetorix’s men sallying forth from Alesia had equipped themselves with fascines and bundles of brush with which to fill in the broad ditch that blocked their path, but the work went too slowly and as dawn arrived and their compatriots outside withdrew, they found themselves forced to retreat as well.
Two attempts had been made on the Roman fortifications, and both had failed. What was more neither of the attacks had seemed to put undue pressure on the Roman defences. Another strategy was called for. The four main Gallic chieftains came together to discuss the best way forward, taking counsel from local tribesmen about the lie of the land and how the Romans had constructed their works upon it. Through such a process a potential weakness was found: on the north-western side a large hill had proved too substantial an object for Caesar’s engineers to include within his defences. His men had been forced to build their walls along the gentle slopes at the hill’s base, giving any attack from that angle an advantage of height over the defenders. Further reconnaissance confirmed that the Roman works on the north-western side were not as robust or as deep as those on the western plain.
A plan of attack was quickly drawn up; the operation would consist of a two-pronged assault set for noon on the following day (18 October). The bulk of the Gallic army including all its horse would make its way towards the western approaches once more, threatening the main camp that anchored that section of the Roman line, while another force would launch a simultaneous surprise attack on the north-western section of the fortifications. It was reasonable to expect that Vercingetorix, seeing an attack developing against the outer walls, would launch his own assaults against the same sections of the inner walls to maximize the pressure felt by the Romans, much as he had done during the night attack the day before. Vercassivellaunus, one of the army’s four commanders and a kinsman of Vercingetorix, was given the honour of leading the northern assault; his force would consist of 60,000 men, hand-picked from the bravest of the Gallic tribes, and equipped with the tools they would need to scale the Roman defences and tear down their wicker walls and watchtowers. Leaving the Gallic camp under cover of darkness, Vercassivellaunus and his men made their way in a broad loop around the western plain, coming to rest just behind the large hill that disrupted the Roman defences in the north-west of their line. There they settled down to recuperate and prepare for the sun to reach its zenith.
Soon enough the western plain was covered with parading Gauls, their cavalry charging towards the outer wall, while Vercassivellaunus and his horde burst from their position of concealment and moved with great speed towards the north-west section of the wall. As expected, as soon as Vercingetorix observed the developing attacks, ‘he moved out of the town, taking with him the hurdles, poles, mantlets, grappling-hooks, and all the other appliances prepared for the sally’ (Caesar, CBG 7.84), his men striking to the west and the north-west in support of the main assaults. Fighting quickly developed along the western and northern sides of the walls, sorely testing the thinly stretched legionaries who were particularly unnerved by the sounds of battle going on behind them, but about which they could do nothing except rely on the steadfastness of their comrades.
Caesar invests his account of the battle with heightened drama, with each side understanding that this was its last chance to secure victory, something that may not have been too far from the truth considering the size of the forces committed to the battle. The section of the line that Vercassivellaunus was attacking was under the control of the legates Gaius Antistius Reginus and Gaius Caninius Rebilus; though they each had one legion at their command, they were seriously outnumbered by the Gauls. In addition, the fact that they were advancing down a slope towards the Roman wall allowed some of the Gauls to launch showers of arrows and javelins from favourable positions, while others formed themselves into a testudo and moved against the fortifications; ‘fresh men quickly replaced the exhausted. Earth cast by the [Gallic soldiers] over the entrenchments gave the Gauls a means of ascent and at the same time covered over the appliances which the Romans had concealed in the ground; and our troops had now neither arms nor strength enough’ (Caesar, CBG 7.85).
Caesar had positioned himself to ensure that he could see what was happening across the whole of the battle, and it quickly became clear to him that Vercassivellaunus’s attack was the most urgent threat. He despatched Titus Labienus with six cohorts to offer immediate support to the buckling section, ordering him to hold if possible but as a last resort to pull all the defending cohorts out of the camp and fight his way out, a sign of how serious the battle in the north had become. Positioned as they were between the two rings of entrenchments, Caesar’s army had the benefit of interior lines when operating against both Vercingetorix’s force at Alesia and the Gauls on the western plain; but the legions had a great deal of terrain to defend, and if the Gauls applied enough pressure on multiple points for enough time, the strain would be too much. The line would break. Personal exhortations by Caesar helped bolster the men’s morale, but the pressure continued to build, with Vercingetorix’s Gauls redoubling their efforts to break through their encircling prison:
The enemy on the inner side, despairing of success on the level ground, because of the size of the entrenchments, made an attempt to scale the precipitous parts, conveying thither the appliances they had prepared. They dislodged the defenders of the turrets by a swarm of missiles, filled in the trenches with earth and hurdles, tore down rampart and breastwork with grappling-hooks. (Caesar, CBG 7.86)
Reinforcements of six cohorts were sent at once, followed by a second wave of seven cohorts, but the savagery of the fighting did not abate, forcing Caesar himself to take command of a relief column of cohorts and join in the battle; his presence and the extra legionaries eventually made the difference, stabilizing the situation and ensuring that the worst of Vercingetorix’s attack was beaten back.
With the wall of contravallation secured, Caesar turned his attention back to the north-western circumvallation where Vercassivellaunus’s Gauls were causing such havoc. The defences there had been mostly overwhelmed by the Gallic tactics, their numbers and aggression, with neither the earthworks nor the ditches able to stem their advance. Titus Labienus was holding on, but with difficulty; aside from the existing forces at his disposal he had added 11 more cohorts from a nearby camp, but by this stage he may well have been fighting in the ‘safe’ ground between the inner and outer walls. He sent a messenger to Caesar with a description of the circumstances he was facing, and what he thought needed to be done.
Wasting no time, Caesar ordered four cohorts of infantry from the nearest fort together with a portion of the cavalry to follow him; the remainder of the cavalry he instructed to leave the Roman lines and circle around behind the Gallic position, so as to attack them from the rear. Caesar, clearly identifiable in his commander’s cloak, led his four cohorts and cavalry contingent straight towards Titus Labienus and the heart of the battle. The Gauls, with their better vantage point on the high ground north of the outer wall, could clearly observe the arrival of Caesar and his reinforcements, a sight which encouraged them to redouble their efforts; ‘a shout was raised on both sides, and taken up by an answering shout from the rampart and the whole of the entrenchments’ (Caesar, CBG 7.88), as both sides came together once again. The sudden appearance of Caesar’s Germanic cavalry approaching the rear of the Gallic host caused consternation and panic to ripple throughout their ranks. At around the same time the pressure from the four new cohorts began to tell; the legionaries, having discarded their pila, instead closed in with their gladii, and this new assault coupled with the cavalry threat to their rear caused the Gauls to fall back. Unfortunately, their path to safety lay through Caesar’s fast-approaching Germanic horsemen, who crashed into the Gauls’ disorganized lines, wreaking mayhem among them.
The rout quickly descended into a slaughter, with 74 Gallic war standards captured, together with Vercassivellaunus himself. Vercingetorix’s men, seeing the disaster unfold before them, abandoned their attempts to overwhelm the contravallation’s entrenchments and retreated back to their fastness on the plateau. As soon as news of the scattering and destruction of the northern force reached the main body of the Gallic relief army, it broke camp and retreated in relative safety, Caesar’s men being too worn out to engage in any sort of immediate pursuit.
The Gallic collapse was near total, as much a defeat of the spirit as of the flesh. The men at Alesia were taken into captivity, many of those from the relief army hunted down and scattered. Despite the fact that it would take two more years of campaigning, Caesar’s domination of Gaul was all but assured by his victory at Alesia. Vercingetorix had come very close, perhaps as close as Boduognatus had at the Sabis five years earlier, to breaking Roman power in Gaul, but the flexibility, speed, discipline and engineering prowess of the legions had withstood him. Vercingetorix surrendered to Caesar, but his hopes for mercy were met with chains and captivity, the final blow falling some years later. After being paraded through the streets of Rome as the prize exhibit in Caesar’s Gallic Triumph, he was taken away and quietly strangled, as was the Roman fashion.