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
Extension of the Roman Territory
The brave and impassioned Italian race doubtless never lacked feuds among themselves and with their neighbours: as the country flourished and civilization advanced, feuds must have become gradually changed into war and raids for pillage into conquest, and political powers must have begun to assume shape. No Italian Homer, however, has preserved for us a picture of these earliest frays and plundering excursions, in which the character of nations is moulded and expressed like the mind of the man in the sports and enterprises of the boy; nor does historical tradition enable us to form a judgment, with even approximate accuracy, as to the outward development of power and the comparative resources of the several Latin cantons.
It is only in the case of Rome, at the utmost, that we can trace in some degree the extension of its power and of its territory. The earliest demonstrable boundaries of the united Roman community have been already stated;(1) in the landward direction they were on an average just about five miles distant from the capital of the canton, and it was only toward the coast that they extended as far as the mouth of the Tiber (-Ostia-), at a distance of somewhat more than fourteen miles from Rome.
1. Cf. I. IV. Earliest Limits of the Roman Territory
"The new city," says Strabo, in his description of the primitive Rome, "was surrounded by larger and smaller tribes, some of whom dwelt in independent villages and were not subordinate to any national union." It seems to have been at the expense of these neighbours of kindred lineage in the first instance that the earliest extensions of the Roman territory took place.
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Reference address : https://www.ellopos.net/elpenor/rome/1-07-hegemony-rome-latium.asp