The Roman camp among the Sequani had its inevitable effect, and before the end of winter, Labienus had informed Caesar that the Belgae were exchanging oaths and hostages (BG 2.1.1). In the campaign against the Belgae in 57, Caesar pursued them with three legions and with the cavalry under Pedius and Cotta caused great destruction (2.11). When the Nervii surprised the Romans near the Sabis, Labienus happened to be on the left wing with the ninth and tenth legions. He defeated the Atrebates opposing him, crossed the river and captured the enemy camp (BC 2.23.1–1) From that height he saw that the right wing was being hard pressed by the Nervii and sent the tenth against their rear (2.26.1–5). His action turned the battle, inflicting heavy losses upon the Nervii (2.27.1; 28.2).
The Belgian campaign is told in a straightforward fashion. The caution and patience displayed against the Helvetii combined to be the best strategy against the Belgae who were pressed by numbers and shortage of food. No attempt to detract from the success of the pursuit need be found in the words sine ullo periculo (without any danger) (1.11.6). As Caesar explains, only the Belgae in the rear resisted (2.11.4–6), and undisciplined flights following a rout always resulted in much slaughter.[23]
The account of the defense against the Nervii, however, was intended to exculpate Caesar from two errors: faulty scouting, which led him to misjudge the size of the enemy force, and failure to draw up a line of battle to protect those who were entrenching the camp.[24] Caesar was taken completely off guard. But the narrative emphasizes that Caesar did all that was required with speed to match the enemy’s (2.19.7):
incredibili celeritate . . . ut paene uno tempore et ad silvas et in flumine et iam in manibus nostris hostes viderentur;