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
Relations of the Etruscans to Latium
From the time at which the river Tiber became the line of demarcation between Etruria on the one side and Umbria and Latium on the other, peaceful relations probably upon the whole prevailed in that quarter, and no essential change seems to have taken place in the boundary line, at least so far as concerned the Latin frontier.
Vividly as the Romans were impressed by the feeling that the Etruscan was a foreigner, while the Latin was their countryman, they yet seem to have stood in much less fear of attack or of danger from the right bank of the river than, for example, from their kinsmen in Gabii and Alba; and this was natural, for they were protected in that direction not merely by the broad stream which formed a natural boundary, but also by the circumstance, so momentous in its bearing on the mercantile and political development of Rome, that none of the more powerful Etruscan towns lay immediately on the river, as did Rome on the Latin bank.
The Veientes were the nearest to the Tiber, and it was with them that Rome and Latium came most frequently into serious conflict, especially for the possession of Fidenae, which served the Veientes as a sort of -tete de pont- on the left bank just as the Janiculum served the Romans on the right, and which was sometimes in the hands of the Latins, sometimes in those of the Etruscans. The relations of Rome with the somewhat more distant Caere were on the whole far more peaceful and friendly than those which we usually find subsisting between neighbours in early times.
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Reference address : http://www.ellopos.net/elpenor/rome/1-09-etruscans.asp?pg=10