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
Caesar, who had reason for not altogether trusting his staff of officers, had at the very outset sent away all the officers' horses, so as to make the necessity of holding their ground thoroughly clear to his troops; in fact the battle, had the Romans lost it, would have probably brought about the annihilation of the Roman army.
The Roman troops were too much exhausted to pursue the conquered with vigour; but in consequence of the proclamation of Caesar that he would treat all who should support the Helvetii as like the Helvetii themselves enemies of the Romans, all support was refused to the beaten army whithersoever it went-- in the first instance, in the canton of the Lingones (about Langres)--and, deprived of all supplies and of their baggage and burdened by the mass of camp-followers incapable of fighting, they were under the necessity of submitting to the Roman general.
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Reference address : https://www.ellopos.net/elpenor/rome/5-07-subjugation-west.asp?pg=66