On the other hand, the party in Gaul hostile to the Romans, which hoped to obtain a powerful reinforcement in the Helvetii, more especially the Haeduan Dumnorix brother of Divitiacus, and at the head of the national party in his canton as the latter wasat the head of the Romans, procured for them a passage through the passes of the Jura and the territory of the Sequani. The Romans had no legal title to forbid this; but other and higher interestswereat stake for them in the Helvetic expedition than the question of the formal integrity of the Roman territory - interests which could only be guarded, if Caesar, instead of confining himself, as all the governors of the senate and even Marius[34] had done, to the modest task of watching the frontier, should cross what had hitherto been the frontier at the head of a considerable army. Caesar was general not of the senate, but of the state; he showed no hesitation. He had immediately proceeded from Genava in person to Italy, and with characteristic speed brought up the three legions cantoned there as well as two newly-formed legions of recruits.
These troops he united with the corps stationed at Genava, and crossed the Rhone with his whole force. His unexpected appearance in the territory of the Haedui naturally at once restored the Roman party there to power, which was not unimportant as regarded supplies. He found the Helvetii employed in crossing the Saone, and moving from the territory of the Sequani into that of the Haedui; those of them that were still on the left bank of the Saone, especially the corps of the Tigorini, were caught and destroyed by the Romans rapidly advancing. The bulk of the expedition, however, had already crossed to the right bank of the river; Caesar followed them and in twenty-four hours effected the passage, which the unwieldy host of the Helvetii had not been able to accomplish in twenty days. The Helvetii, prevented by this passage of the river on the part of the Roman army from continuing their march westward, turned in a northerly direction, doubtless under the supposition that Caesar would not venture to follow them far into the interior of Gaul, and with the intention, if he should desist from following them, of turning again toward their proper destination. For fifteen days the Roman army marched behind that of the enemy at a distance of about four miles, clinging to its rear, and hoping for an advantageous opportunity of assailing the Helvetic host under conditions favourable to victory, and destroying it. But this moment came not: unwieldy as was the march of the Helvetic caravan, the leaders knew how to guard against a surprise, and appeared to be copiously provided with supplies as well as most accurately informed by their spies of every event in the Roman camp. On the other hand the Romans began to suffer from want of necessaries, especially when the Helvetii removed from the Saone and the means of river-transport ceased. The non-arrival of the supplies promised by the Haedui, from which this embarrassment primarily arose, excited the more suspicion, as both armies were still moving about in their territory. Moreover the considerable Roman cavalry, numbering almost 4000 horse, proved utterly untrustworthy - which doubtless admitted of explanation, for they consisted almost wholly of Celtic horsemen, especially of the mounted retainers of the Haedui, under the command of Dumnorix the well-known enemy of the Romans, and Caesar himself had taken them over still more as hostages than as soldiers. There was good reason to believe that a defeat which they suffered at the hands of the far weaker Helvetic cavalry was occasioned by themselves, and that the enemy was informed by them of all occurrences in the Roman camp. The position of Caesar grew critical; it was becoming disagreeably evident, how much the Celtic patriot party could effect even with the Haedui in spite of their official alliance with Rome, and of the distinctive interests of this canton inclining it towards the Romans; what was to be the issue, if they ventured deeper and deeper into a country full of excitement, and if they removed daily farther from their means of communication?
The armies were just marching past Bibracte (Autun), the capital of the Haedui, at a moderate distance; Caesar resolved to seize this important place by force before he continued his march into the interior; and it is very possible, that he intended to desist altogether from farther pursuit and to establish himself in Bibracte. But when he ceased from the pursuit and turned against Bibracte, the Helvetii thought that the Romans were making preparations for flight, and now attacked in their turn.
Caesar desired nothing better. The two armies posted themselves on two parallel chains of hills; the Celts began the engagement, broke up the Roman cavalry which had advanced into the plain, and rushed on against the Roman legions posted on the slope of the hill, but were there obliged to give way before Caesar's veterans. When the Romans thereupon, following up their advantage, descended in their turn to the plain, the Celts again advanced against them, and a reserved Celtic corps took them at the same time in flank.
The reserve of the Roman attacking column was pushed forward against the latter; it forced it away from the main body towards the baggage and the barricade of waggons, where it was destroyed. The bulk of the Helvetic host was at length brought to give way, and compelled to beat a retreat in an easterly direction - the opposite of that towards which their expedition led them. This day had frustrated the scheme of the Helvetii to establish for themselves new settlements on the Atlantic Ocean, and handed them over to the pleasure of the victor; but it had been a hot day also for the conquerors. Caesar, who had reason for not altogether trusting his staff of officers, had at the very outset sent away all the officers' horses, so as to make the necessity of holding their ground thoroughly clear to his troops; in fact the battle, had the Romans lost it, would have probably brought about the annihilation of the Roman army. The Roman troops were too much exhausted to pursue the conquered with vigour; but in consequence of the proclamation of Caesar that he would treat all who should support the Helvetii as like the Helvetii themselves enemies of the Romans, all support was refused to the beaten army whithersoever it went - in the first instance, in the canton of the Lingones (about Langres) - and, deprived of all supplies and of their baggage and burdened by the mass of camp-followers incapable of fighting, they were under the necessity of submitting to the Roman general.
34. IV. V. The Cimbri, Teutones, and Helvetii Unite.