During the winter of 58–57 BC rumours came to Caesar's ears that the Belgae tribes were forming a union because they feared possible Roman interference in their affairs.

In response, the other Belgae and Celtic tribes had attacked Bibrax (the oppidum of the Remi, situated near the river Aisne, then known as the Axona).

As Caesar's forces were outnumbered and thus at risk of being out-flanked, he had his army build two trenches, each 400 paces long, one on each side of the plain before the Roman camp.

Caesar claims their intention was to lead a part of their force over the bridge, and either take the camp by storm, or cut the Romans off from the lands on the opposite side of the river.

This action is described in his Gallic Wars at 2.10: Caesar, being apprized of [the situation] by Titurius [his legate], leads all his cavalry and light-armed Numidians, slingers and archers, over the bridge, and hastens toward them.

By the immense number of their missiles they drove back the rest, who, in a most courageous manner were attempting to pass over their bodies, and surrounded with their cavalry, and cut to pieces those who had first crossed the river.

Then, calling a council of war, they immediately resigned to returning to their home territories, where they might better be able to engage Caesar's invading army.