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
While the Roman power by sea was thus very far from keeping pace with the immense development of their power by land, and the war marine belonging to the Romans in particular was by no means such as from the geographical and commercial position of the city it ought to have been, yet it began gradually to emerge out of the complete nullity to which it had been reduced about the year 400; and, considering the great resources of Italy, the Phoenicians might well follow its efforts with anxious eyes.
The crisis in reference to the supremacy of the Italian waters was approaching; by land the contest was decided. For the first time Italy was united into one state under the sovereignty of the Roman community. What political prerogatives the Roman community on this occasion withdrew from all the other Italian communities and took into its own sole keeping, or in other words, what conception in state-law is to be associated with this sovereignty of Rome, we are nowhere expressly informed, and--a significant circumstance, indicating prudent calculation--there does not even exist any generally current expression for that conception.(24)
24. The clause, by which a dependent people binds itself "to uphold in a friendly manner the sovereignty of that of Rome" (-maiestatem populi Romani comiter conservare-), is certainly the technical appellation of that mildest form of subjection, but it probably did not come into use till a considerably later period (Cic. pro Balbo, 16, 35). The appellation of clientship derived from private law, aptly as in its very indefiniteness it denotes the relation (Dig. xlix. 15, 7, i), was scarcely applied to it officially in earlier times.
The only privileges that demonstrably belonged to it were the rights of making war, of concluding treaties, and of coining money. No Italian community could declare war against any foreign state, or even negotiate with it, or coin money for circulation. On the other hand every declaration of war made by the Roman people and every state-treaty resolved upon by it were binding in law on all the other Italian communities, and the silver money of Rome was legally current throughout all Italy. It is probable that the formulated prerogatives of the leading community extended no further. But to these there were necessarily attached rights of sovereignty that practically went far beyond them.
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Reference address : https://www.ellopos.net/elpenor/rome/2-07-pyrrhus-rome-italy.asp?pg=66