Even before the winter was at an end, he threw himself on the Boii settled by Caesar in the territory of the Haedui, with the view of annihilating these, almost the sole trustworthy allies of Rome, before Caesar came up. The news of this attack induced Caesar, leaving behind the baggage and two legions in the winter quarters of Agedincum (Sens), to march immediately and earlier than he would doubtless otherwise have done, against the insurgents. He remedied the sorely-felt want of cavalry and light infantry in some measure by gradually bringing up German mercenaries, who instead of using their own small and weak ponies were furnished with Italian and Spanish horses partly bought, partly procured by requisition of the officers. Caesar, after having by the way caused Cenabum, the capital of the Carnutes, which had given the signal for the revolt, to be pillaged and laid in ashes, moved over the Loire into the country of the Bituriges. He thereby induced Vercingetorix to abandon the siege of the town of the Boii, and to resort likewise to the Bituriges. Here the new mode of warfare was first to be tried. By order of Vercingetorix more than twenty townships of the Bituriges perished in the flames on one day; the general decreed a similar self-devastation as to the neighbour cantons, so far as they could be reached by the Roman foraging parties.
According to his intention, Avaricum (Bourges), the rich and strong capital of the Bituriges, was to meet the same fate; but the majority of the war-council yielded to the suppliant entreaties of the Biturigian authorities, and resolved rather to defend that city with all their energy. Thus the war was concentrated in the first instance around Avaricum, Vercingetorix placed his infantry amidst the morasses adjoining the town in a position so unapproachable, that even without being covered by the cavalry they needed not to fear the attack of the legions. The Celtic cavalry covered all the roads and obstructed the communication. The town was strongly garrisoned, and the connection between it and the army before the walls was kept open. Caesar's position was very awkward.
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.
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.