But when he heard that the Belgae, who were the most powerful of the Gauls and occupied the third part of all their country, had revolted, and had assembled unknown myriads of armed men, he turned back at once and marched thither with great speed. Caesar’s campaign against the Belgae, in 57 B.C., is described by himself in B. G. ii. 1-33 . He fell upon the enemy as they were plundering the Gauls that were in alliance with Rome, and so routed and destroyed the least scattered and most numerous of them, after a disgraceful struggle on their part, that the Romans could cross lakes and deep rivers for the multitude of dead bodies in them. All the rebels who dwelt along the ocean submitted without a battle; against the Nervii, however, the most savage and warlike of the people in these parts, Caesar led his forces. The Nervii, who dwelt in dense woods, and had placed their families and possessions in a recess of the forest at farthest remove from the enemy, at a time when Caesar was fortifying a camp and did not expect the battle, fell upon him suddenly, sixty thousand strong. They routed his cavalry, and surrounded the seventh and twelfth legions and slew all their centurions,