II. Cæsar, learning that the Helvetii intended to pass through the Roman province, left Rome hastily in the month of March, hurried by forced marches into Transalpine Gaul, and, according to Plutarch, reached Geneva in eight days.[160] As he had in the province only a single legion, he ordered a levy of as many men as possible, and then destroyed the bridge of Geneva. Informed of his arrival, the Helvetii, who were probably not yet all assembled, sent their men of noblest rank to demand a passage through the country of the Allobroges, promising to commit no injury there; they had, they said, no other road to quit their country. Cæsar was inclined to refuse their demand at once, but he called to mind the defeat and death of the Consul L. Cassius; and wishing to obtain time to collect the troops of which he had ordered the levy, he gave them hopes of a favourable reply, and adjourned it to the Ides of April (8th of April). By this delay he gained a fortnight; it was employed in fortifying the left bank of the Rhone, between Lake Léman and the Jura.[161] If we estimate at 5,000 men the legion which was in the province, and at 5,000 or 6,000 the number of soldiers of the new levies, we see that Cæsar had at his disposal, to defend the banks of the Rhone, about 10,000 or 11,000 infantry.[162]
Description of the Retrenchment of the Rhone.
III. The distance from Lake Léman to the Jura, following the sinuosities of the river, is 29½ kilomètres, or 19,000 Roman paces (millia passuum decem novem).[163] It is on the space comprised between these two points that a retrenchment was raised which is called in the “Commentaries” murus fossaque. This could not be a continuous work, as the ground to be defended is intersected by rivers and ravines, and the banks of the Rhone are almost everywhere so precipitous that it would have been useless to fortify them. Cæsar, pressed for time, can only have made retrenchments on the weakest points of the line where the passage of the river was easy; indeed, this is what Dio Cassius tells us.[164] The labours of the Romans were only supplementary, on certain points, to the formidable natural obstacles which the Rhone presents in the greater part of its course. The only places where an attempt could be made to pass it, because the heights there sink towards the banks of the river into practicable declivities, are situated opposite the modern villages of Russin, Cartigny, Avully, Chancy, and Cologny. In these places they cut the upper part of the slope into a perpendicular, and afterwards hollowed a trench, the scarp of which thus gained an elevation of sixteen feet. These works, by uniting the escarpments of the Rhone, formed, from Geneva to the Jura, a continuous line, which presented an impassable barrier. Behind and along this line, at certain distances, posts and closed redoubts rendered it impregnable. (See Plate 3.)[165]
This retrenchment, which required only from two to three days’ labour, was completed when the deputies returned, at the time appointed, to hear Cæsar’s reply. He flatly refused the passage, declaring that he would oppose it with all his means.
Meanwhile the Helvetii, and the people who took part in their enterprise, had assembled on the right bank of the Rhone. When they learnt that they must renounce the hope of quitting their country without opposition, they resolved to open themselves a passage by force. Several times—sometimes by day, and sometimes by night—they crossed the Rhone, some by fording, others with the aid of boats joined together, or of a great number of rafts of timber, and attempted to carry the heights, but, arrested by the strength of the retrenchment (operis munitione), and by the efforts and missiles of the soldiers who hastened to the threatened points (concursu et telis), they abandoned the attack.[166]
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]