Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
The Conflict with the Nervii
But in the eastern cantons the national feeling was more energetically roused. The Viromandui (about Arras), the Atrebates (about St. Quentin), the German Aduatuci (about Namur), but above all the Nervii (in Hainault) with their not inconsiderable body of clients, little inferior in number to the Suessiones and Bellovaci, far superior to them in valour and vigorous patriotic spirit, concluded a second and closer league, and assembled their forces on the upper Sambre. Celtic spies informed them most accurately of the movements of the Roman army; their own local knowledge, and the high tree-barricades which were formed everywhere in these districts to obstruct the bands of mounted robbers who often visited them, allowed the allies to conceal their own operations for the most part from the view of the Romans.
When these arrived on the Sambre not far from Bavay, and the legions were occupied in pitching their camp on the crest of the left bank, while the cavalry and light infantry were exploring the opposite heights, the latter were all at once assailed by the whole mass of the enemy's forces and driven down the hill into the river. In a moment the enemy had crossed this also, and stormed the heights of the left bank with a determination that braved death. Scarcely was there time left for the entrenching legionaries to exchange the mattock for the sword; the soldiers, many without helmets, had to fight just as they stood, without line of battle, without plan, without proper command; for, owing to the suddenness of the attack and the intersection of the ground by tall hedges, the several divisions had wholly lost their communications.
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Reference address : https://www.ellopos.net/elpenor/rome/5-07-subjugation-west.asp?pg=77