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
Besides this, two reserves were formed, the first at Falerii, the second under the walls of the capital. The rendezvous of the Italians was Umbria, towards which the roads from the Gallic, Etruscan, and Sabellian territories converged; towards Umbria the consuls also moved off their main force, partly along the left, partly along the right bank of the Tiber, while at the same time the first reserve made a movement towards Etruria, in order if possible to recall the Etruscan troops from the main scene of action for the defence of their homes.
The first engagement did not prove fortunate for the Romans; their advanced guard was defeated by the combined Gauls and Samnites in the district of Chiusi. But that diversion accomplished its object. Less magnanimous than the Samnites, who had marched through the ruins of their towns that they might not be absent from the chosen field of battle, a great part of the Etruscan contingents withdrew from the federal army on the news of the advance of the Roman reserve into Etruria, and its ranks were greatly thinned when the decisive battle came to be fought on the eastern declivity of the Apennines near Sentinum.
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Reference address : https://www.ellopos.net/elpenor/rome/2-06-italians-rome.asp?pg=34