Plutarch Caesar 20

[1] After this achievement, Caesar left his forces among the Sequani to spend the winter, ¹ while he himself, desirous of giving attention to matters at Rome, came down to Gaul along the Po, ² which was a part of the province assigned to him; for the river called Rubicon separates the rest of Italy from Cisalpine Gaul.

[2] Here he fixed his quarters and carried on his political schemes. Many came to see him, and he gave each one what he wanted, and sent all away in actual possession of some of his favours and hoping for more. And during all the rest of the time of his campaigns in Gaul, unnoticed by Pompey, he was alternately subduing the enemy with the arms of the citizens, or capturing and subduing the citizens with the money which he got from the enemy.

[3]
  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. ³ 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.

[4] 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,

[5] and had not Caesar snatched a shield, ⁴ made his way through the combatants in front of him, and hurled himself upon the Barbarians; and had not the tenth legion, at sight of his peril, run down from the heights and cut the ranks of the enemy to pieces, not a Roman, it is thought, would have survived. As it was, however, owing to Caesar’s daring, they fought beyond their powers, as the saying is, and even then did not rout the Nervii, but cut them down as they defended themselves; for out of sixty thousand only five hundred are said to have come off alive, and only three of their senators out of four hundred.