Plutarch Caesar 25

[1] The numerous revolts of the Gauls in those parts were quieted by this success, as well as by the fact that Caesar himself, during the winter, went about in all directions and kept close watch on the disturbers of the peace. For there had come from Italy three legions to replace the men that he had lost, Pompey having lent two of those under his command, and one having been newly levied in Gaul about the Po.

[2] But in remoter regions ¹ the germs of the greatest and most dangerous of the wars waged in those parts began to show themselves. They had for a long time been secretly sown and cultivated by the most influential men among the most warlike tribes, and derived strength from large bodies of young men assembled from all sides in arms, from great riches brought together, from strong cities, and from countries which were hard to invade.

[3] At that season of winter, too, frozen rivers, forests buried in snow, plains converted into lakes by winter torrents, in some parts paths obliterated by deep snow, and in others the great uncertainty of a march through swamps and streams diverted from their courses, all seemed to make it wholly impossible for Caesar to oppose the plans of the rebels. Accordingly, many tribes had revolted, but the head and front of the revolt were the Arverni and Carnuntini, ² and Vergentorix was chosen to have the entire authority in the war. His father the Gauls had put to death because they thought he was aiming at a tyranny.