[Sidenote: The Helvetii begin their March towards the Saône. Cæsar unites his Troops.]
IV. The only road which now remained was that which lay across the country of the Sequani (the Pas-de-l'Ecluse); but this narrow defile could not be passed without the consent of its inhabitants. The Helvetii charged the Æduan Dumnorix, the son-in-law of Orgetorix, to solicit it for them. High in credit among the Sequani, Dumnorix obtained it; and the two peoples entered into an engagement, one to leave the passage free, the other to commit no disorder; and, as pledges of their convention, they exchanged hostages.[167]
When Cæsar learned that the Helvetii were preparing to pass through the lands of the Sequani and the Ædui on their way to the Santones, he resolved to oppose them, unwilling to suffer the establishment of warlike and hostile men in a fertile and open country, neighbouring upon that of the Tolosates, which made part of the Roman province.[168]
But, as he had not at hand sufficient forces, he resolved on uniting all the troops he could dispose of in his vast command. He entrusts, therefore, the care of the retrenchments on the Rhone to his lieutenant T. Labienus, hastens into Italy by forced marches, raises there in great haste two legions (the 11th and 12th), brings from Aquileia, a town of Illyria,[169] the three legions which were there in winter quarters (the 7th, 8th, and 9th), and, at the head of his army, takes across the Alps (_see Plate 4_) the shortest road to Transalpine Gaul.[170] The Centrones, the Graioceli, and the Caturiges (see _page_ 24, _note_), posted on the heights,[171] attempt to bar his road; but he overthrows them in several engagements, and from Ocelum (_Usseau_),[172] the extreme point of the Cisalpine, reaches in seven days the territory of the Vocontii, making thus about twenty-five kilomètres a day. He next penetrates into the country of the Allobroges, then into that of the Segusiavi, who bordered on the Roman province beyond the Rhone.[173]
These operations took two months;[174] the same time had been employed by the Helvetii in negotiating the conditions of their passage through the country of the Sequani, moving from the Rhone to the Saône, and beginning to pass the latter river. They had passed the Pas-de-l'Ecluse, followed the right bank of the Rhone as far as Culoz, then turned to the east through Virieu-le-Grand, Tenay, and Saint-Rambert, and, thence crossing the plains of Ambérieux, the river Ain, and the vast plateau of the Dombes, they had arrived at the Saône, the left bank of which they occupied from Trévoux to Villefranche. (_See Plate 4._) The slowness of their march need not surprise us if we consider that an agglomeration of 368,000 individuals, men, women, and children, dragging after them from 8,000 to 9,000 wagons, through a defile where carriages could only pass one abreast, would necessarily employ several weeks in passing it.[175] Cæsar, no doubt, calculated beforehand, with sufficient accuracy, the time it would take them to gain the banks of the Saône; and we may therefore suppose that, at the moment when he repaired into Italy, he hoped to bring thence his army in time to prevent them from passing that river.