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
The connections and gold of the Carthaginians, moreover, brought to them excellent Numidian horsemen in troops, and also numerous Greek mercenaries; amongst whom was the celebrated captain Xanthippus of Sparta, whose talent for organization and strategical skill were of great service to his new masters.(6)
6. The statement, that the military talent of Xanthippus was the primary means of saving Carthage, is probably coloured; the officers of Carthage can hardly have waited for foreigners to teach them that the light African cavalry could be more appropriately employed on the plain than among hills and forests. From such stories, the echo of the talk of Greek guardrooms, even Polybius is not free. The statement that Xanthippus was put to death by the Carthaginians after the victory, is a fiction; he departed voluntarily, perhaps to enter the Egyptian service.
While the Carthaginians were thus making their preparations in the course of the winter, the Roman general remained inactive at Tunes. Whether it was that he did not anticipate the storm which was gathering over his head, or that a sense of military honour prohibited him from doing what his position demanded--instead of renouncing a siege which he was not in a condition even to attempt, and shutting himself up in the stronghold of Clupea, he remained with a handful of men before the walls of the hostile capital, neglecting even to secure his line of retreat to the naval camp, and neglecting to provide himself with --what above all he wanted, and what might have been so easily obtained through negotiation with the revolted Numidian tribes --a good light cavalry. He thus wantonly brought himself and his army into a plight similar to that which formerly befell Agathocles in his desperate adventurous expedition.
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Reference address : https://www.ellopos.net/elpenor/rome/3-02-war-rome-carthage-sicily.asp?pg=33