Prominent among them, and dwelling in the division occupied by the Celts, were the Helvetii, the Sequani and the Aedui, in the basins of the Rhodanus and its tributary the Arar (Saone), who, he says, were reckoned the three most powerful nations in all Gaul; the Arverni in the mountains of Cebenna; the Senones and Carnutes in the basin of the Liger; the Veneti and other Armorican tribes between the mouths of the Liger and Sequana.
6-7) who tells us that it was the last oppidum of the Allobroges, and the nearest to the territory of the Helvetii, with which it was connected by a bridge that, for military reasons, he was forced to destroy.
In 58 B.C. the Helvetii, a Celtic people inhabiting Switzerland, determined to migrate for the shores of the Atlantic and demanded a passage through Roman territory.
With this he marched to Geneva, destroyed the bridge over the Rhone, fortified the left bank of the river, and forced the Helvetii to follow the right bank.
Hastening back to Italy he withdrew his three remaining legions from Aquileia, raised two more, and, crossing the Alps by forced marches, arrived in the neighbourhood of Lyons to find that three-fourths of the Helvetii had already crossed the Saone, marching westward.