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
Maritime Supremacy of the Tarentines and Syracusans - Dionysius of Syracuse
While these extraordinary successes against the Carthaginians and Etruscans placed Syracuse at the head of the Greek cities in Sicily, the Doric Tarentum rose to undisputed pre-eminence among the Italian Greeks, after the Achaean Sybaris had fallen about the time of the expulsion of the kings from Rome (243). The terrible defeat of the Tarentines by the Iapygians (280), the most severe disaster which a Greek army had hitherto sustained, served only, like the Persian invasion of Greece, to unshackle the whole might of the national spirit in the development of an energetic democracy.
Thenceforth the Carthaginians and the Etruscans were no longer paramount in the Italian waters; the Tarentines predominated in the Adriatic and Ionic, the Massiliots and Syracusans in the Tyrrhene, seas. The latter in particular restricted more and more the range of Etruscan piracy. After the victory at Cumae, Hiero had occupied the island of Aenaria (Ischia), and by that means interrupted the communication between the Campanian and the northern Etruscans.
About the year 302, with a view thoroughly to check Tuscan piracy, Syracuse sent forth a special expedition, which ravaged the island of Corsica and the Etruscan coast and occupied the island of Aethalia (Elba). Although Etrusco-Carthaginian piracy was not wholly repressed--Antium, for example, having apparently continued a haunt of privateering down to the beginning of the fifth century of Rome--the powerful Syracuse formed a strong bulwark against the allied Tuscans and Phoenicians. For a moment, indeed, it seemed as if the Syracusan power must be broken by the attack of the Athenians, whose naval expedition against Syracuse in the course of the Peloponnesian war (339-341) was supported by the Etruscans, old commercial friends of Athens, with three fifty-oared galleys. But the victory remained, as is well known, both in the west and in the east with the Dorians.
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Reference address : https://www.ellopos.net/elpenor/rome/2-04-fall-etruscan-celts.asp?pg=5