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
Establishment of Communications with Italy by the Valais
While Caesar was thus forming the Roman domain in the west by force of arms into a compact whole, he did not neglect to open up for the newly-conquered country--which was destined in fact to fill up the wide gap in that domain between Italy and Spain-communications both with the Italian home and with the Spanish provinces. The communication between Gaul and Italy had certainly been materially facilitated by the military road laid out by Pompeius in 677 over Mont Genevre;(40) but since the whole of Gaul had been subdued by the Romans, there was need of a route crossing the ridge of the Alps from the valley of the Po, not in a westerly but in a northerly direction, and furnishing a shorter communication between Italy and central Gaul.
40. Cf. V. I. Pompeius in Gaul
The way which leads over the Great St. Bernard into the Valais and along the lake of Geneva had long served the merchant for this purpose; to get this road into his power, Caesar as early as the autumn of 697 caused Octodurum (Martigny) to be occupied by Servius Galba, and the inhabitants of the Valais to be reduced to subjection--a result which was, of course, merely postponed, not prevented, by the brave resistance of these mountain-peoples.
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Reference address : https://www.ellopos.net/elpenor/rome/5-07-subjugation-west.asp?pg=85