The attempt to induce the Celtic infantry to fight was unsuccessful; it stirred not from its unassailable lines. Bravely as his soldiers in front of the town trenched and fought, the besieged vied with them in ingenuity and courage, and they had almost succeeded in setting fire to the siege apparatus of their opponents. The task withal of supplying an army of nearly 60,000 men with provisions in a country devastated far and wide and scoured by far superior bodies of cavalry became daily more difficult. The slender stores of the Boii were soon used up; the supply promised by the Haedui failed to appear; the corn was already consumed, and the soldier was placed exclusively on flesh-rations. But the moment was approaching when the town, with whatever contempt of death the garrison fought, could be held no longer. Still it was not impossible to withdraw the troops secretly by night and destroy the town, before the enemy occupied it. Vercingetorix made arrangements for this purpose, but the cry of distress raised at the moment of evacuation by the women and children left behind attracted the attention of the Romans; the departure miscarried.
On the following gloomy and rainy day the Romans scaled the walls, and, exasperated by the obstinate defence, spared neither age nor sex in the conquered town. The ample stores, which the Celts had accumulated in it, were welcome to the starved soldiers of Caesar. With the capture of Avaricum (spring of 702), a first success had been achieved over the insurrection, and according to former experience Caesar might well expect that it would now dissolve, and that it would only be requisite to deal with the cantons individually. After he had therefore shown himself with his whole army in the canton of the Haedui and had by this imposing demonstration compelled the patriot party in a ferment there to keep quiet at least for the moment, he divided his army and sent Labienus back to Agedincum, that in combination with the troops left there he might at the head of four legions suppress in the first instance the movement in the territory of the Carnutes and Senones, who on this occasion once more took the lead; while he himself with the six remaining legions turned to the south and prepared to carry the war into the Arvernian mountains, the proper territory of Vercingetorix.
Labienus moved from Agedincum up the left bank of the Seine with a view to possess himself of Lutetia (Paris), the town of the Parisii situated on an island in the Seine, and from this well-secured position in the heart of the insurgent country to reduce it again to subjection. But behind Melodunum (Melun), he found his route barred by the whole army of the insurgents, which had here taken up a position between unassailable morasses under the leadership of the aged Camulogenus. Labienus retreated a certain distance, crossed the Seine at Melodunum, and moved up its right bank unhindered towards Lutetia; Camulogenus caused this town to be burnt and the bridges leading to the left bank to be broken down, and took up a position over against Labienus, in which the latter could neither bring him to battle nor effect a passage under the eyes of the hostile army.
The Roman main army in its turn advanced along the Allier down into the canton of the Arverni. Vercingetorix attempted to prevent it from crossing to the left bank of the Allier, but Caesar overreached him and after some days stood before the Arvernian capital Gergovia[48]. Vercingetorix, however, doubtless even while he was confronting Caesar on the Allier, had caused sufficient stores to be collected in Gergovia and a fixed camp provided with strong stone ramparts to be constructed for his troops in front of the walls of the town, which was situated on the summit of a pretty steep hill; and, as he had a sufficient start, he arrived before Caesar at Gergovia and awaited the attack in the fortified camp under the wall of the fortress. Caesar with his comparatively weak army could neither regularly besiege the place nor even sufficiently blockade it; he pitched his camp below the rising ground occupied by Vercingetorix, and was compelled to preserve an attitude as inactive as his opponent. It was almost a victory for the insurgents, that Caesar's career of advance from triumph to triumph had been suddenly checked on the Seine as on the Allier. In fact the consequences of this check for Caesar were almost equivalent to those of a defeat.
The Haedui, who had hitherto continued vacillating, now made preparations in earnest to join the patriotic party; the body of men, whom Caesar had ordered to Gergovia, had on the march been induced by its officers to declare for the insurgents; at the same time they had begun in the canton itself to plunder and kill the Romans settled there. Caesar, who had gone with two-thirds of the blockading army to meet that corps of the Haedui which was being brought up to Gergovia, had by his sudden appearance recalled it to nominal obedience; but it was more than ever a hollow and fragile relation, the continuance of which had been almost too dearly purchased by the great peril of the two legions left behind in front of Gergovia. For Vercingetorix, rapidly and resolutely availing himself of Caesar's departure, had during his absence made an attack on them, which had wellnigh ended in their being overpowered, and the Roman camp being taken by storm. Caesar's unrivalled celerity alone averted a second catastrophe like that of Aduatuca. Though the Haedui made once more fair promises, it might be foreseen that, if the blockade should still be prolonged without result, they would openly range themselves on the side of the insurgents and would thereby compel Caesar to raise it; for their accession would interrupt the communication between him and Labienus, and expose the latter especially in his isolation to the greatest peril. Caesar was resolved not to let matters come to this pass, but, however painful and even dangerous it was to retire from Gergovia without having accomplished his object, nevertheless, if it must be done, rather to set out immediately and by marching into the canton of the Haedui to prevent at any cost their formal desertion.
Before entering however on this retreat, which was far from agreeable to his quick and confident temperament, he made yet a last attempt to free himself from his painful perplexity by a brilliant success. While the bulk of the garrison of Gergovia was occupied in intrenching the side on which the assault was expected, the Roman general watched his opportunity to surprise another access less conveniently situated but at the moment left bare. In reality the Roman storming columns scaled the camp-wall, and occupied the nearest quarters of the camp; but the whole garrison was already alarmed, and owing to the small distances Caesar found it not advisable to risk the second assault on the city-wall. He gave the signal for retreat; but the foremost legions, carried away by the impetuosity of victory, heard not or did not wish to hear, and pushed forward without halting, up to the city-wall, some even into the city. But masses more and more dense threw themselves in front of the intruders; the foremost fell, the columns stopped; in vain centurions and legionaries fought with the most devoted and heroic courage; the assailants were chased with very considerable loss out of the town and down the hill, where the troops stationed by Caesar in the plain received them and prevented greater mischief. The expected capture of Gergovia had been converted into a defeat, and the considerable loss in killed and wounded - there were counted 700 soldiers that had fallen, including 46 centurions - was the least part of the misfortune suffered.
48. This place has been sought on a rising ground which is still named Gergoie, a league to the south of the Arvernian capital Nemetum, the modern Clermont; and both the remains of rude fortress-walls brought to light in excavations there, and the tradition of the name which is traced in documents up to the tenth century, leave no room for doubt as to the correctness of this determination of the locality. Moreover it accords, as with the other statements of Caesar, so especially with the fact that he pretty clearly indicates Gergovia as the chief place of the Arverni (vii. 4). We shall have accordingly to assume, that the Arvernians after their defeat were compelled to transfer their settlement from Gergovia to the neighbouring less strong Nemetum.