The west from the mouth of the Garonne to that of the Seine was rapidly infected by the insurrection, and Vercingetorix was recognized by all the cantons there as commander-in-chief; where the common council made any difficulty, the multitude compelled it to join the movement; only a few cantons, such as that of the Bituriges, required compulsion to join it, and these perhaps only for appearance' sake. The insurrection found a less favourable soil in the regions to the east of the upper Loire. Everything here depended on the Haedui; and these wavered. The patriotic party was very strong in this canton; but the old antagonism to the leading of the Arverni counterbalanced their influence - to the most serious detriment of the insurrection, as the accession of the eastern cantons, particularly of the Sequani and Helvetii, was conditional on the accession of the Haedui, and generally in this part of Gaul the decision rested with them. While the insurgents were thus labouring partly to induce the cantons that still hesitated, especially the Haedui, to join them, partly to get possession of Narbo - one of their leaders, the daring Lucterius, had already appeared on the Tarn within the limits of the old province - the Roman commander-in-chief suddenly presented himself in the depth of winter, unexpected alike by friend and foe, on this side of the Alps. He quickly made the necessary preparations to cover the old province, and not only so, but sent also a corps over the snow-covered Cevennes into the Arvernian territory; but he could not remain here, where the accession of the Haedui to the Gallic alliance might any moment cut him off from his army encamped about Sens and Langres. With all secrecy he went to Vienna, and thence, attended by only a few horsemen, through the territory of the Haedui to his troops. The hopes, which had induced the conspirators to declare themselves, vanished; peace continued in Italy, and Caesar stood once more at the head of his army.
But what were they to do? It was folly under such circumstances to let the matter come to the decision of arms; for these had already decidedly irrevocably. They might as well attempt to shake the Alps by throwing stones at them as to shake the legions by means of the Celtic bands, whether these might be congregated in huge masses or sacrificed in detail canton after canton. Vercingetorix despaired of defeating the Romans. He adopted a system of warfare similar to that by which Cassivellaunus had saved the insular Celts. The Roman infantry was not to be vanquished; but Caesar's cavalry consisted almost exclusively of the contingent of the Celtic nobility, and was practically dissolved by the general revolt. It was possible for the insurrection, which was in fact essentially composed of the Celtic nobility, to develop such a superiority in this arm, that it could lay waste the land far and wide, burn down towns and villages, destroy the magazines, and endanger the supplies and the communications of the enemy, without his being able seriously to hinder it. Vercingetorix accordingly directed all his efforts to the increase of his cavalry, and of the infantry-archers who were according to the mode of fighting of that time regularly associated with it. He did not send the immense and self-obstructing masses of the militia of the line to their homes, but he did not allow them to face the enemy, and attempted to impart to them gradually some capacity of intrenching, marching, and manoeuvring, and some perception that the soldier is not destined merely for hand-to-hand combat. Learning from the enemy, he adopted in particular the Roman system of encampment, on which depended the whole secret of the tactical superiority of the Romans; for in consequence of it every Roman corps combined all the advantages of the garrison of a fortress with all the advantages of an offensive army[47]. It is true that a system completely adapted to Britain which had few towns and to its rude, resolute, and on the whole united inhabitants was not absolutely transferable to the rich regions on the Loire and their indolent inhabitants on the eve of utter political dissolution. Vercingetorix at least accomplished this much, that they did not attempt as hitherto to hold every town with the result of holding none; they agreed to destroy the townships not capable of defence before attack reached them, but to defend with all their might the strong fortresses. At the same time the Arvernian king did what he could to bind to the cause of their country the cowardly and backward by stern severity, the hesitating by entreaties and representations, the covetous by gold, the decided opponents by force, and to compel or allure the rabble high or low to some manifestation of patriotism.
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.
47. This, it is true, was only possible, so long as offensive weapons chiefly aimed at cutting and stabbing. In the modern mode of warfare, as Napoleon has excellently explained, this system has become inapplicable, because with our offensive weapons operating from a distance the deployed position is more advantageous than the concentrated. In Caesar's time the reverse was the case.