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
Caesar's fleet, attacked in that roadstead repeatedly by the superior naval force of the enemy, could neither shun the unequal strife, since the loss of the lighthouse-island closed the inner harbour against it, nor yet withdraw, for the loss of the roadstead would have debarred Caesar wholly from the sea. Though the brave legionaries, supported by the dexterity of the Rhodian sailors, had always hitherto decided these conflicts in favour of the Romans, the Alexandrians renewed and augmented their naval armaments with unwearied perseverance; the besieged had to fight as often as it pleased the besiegers, and if the former should be on a single occasion vanquished, Caesar would be totally hemmed in and probably lost.
It was absolutely necessary to make an attempt to recover the lighthouse island. The double attack, which was made by boats from the side of the harbour and by the war-vessels from the seaboard, in reality brought not only the island but also the lower part of the mole into Caesar's power; it was only at the second arch- opening of the mole that Caesar ordered the attack to be stopped, and the mole to be there closed towards the city by a transverse wall. But while a violent conflict arose here around the entrenchers, the Roman troops left the lower part of the mole adjoining the island bare of defenders; a division of Egyptians landed there unexpectedly, attacked in the rear the Roman soldiers and sailors crowded together on the mole at the transverse wall, and drove the whole mass in wild confusion into the sea.
A part were taken on board by the Roman ships; the most were drowned. Some 400 soldiers and a still greater number of men belonging to the fleet were sacrificed on this day; the general himself, who had shared the fate of his men, had been obliged to seek refuge, in his ship, and when this sank from having been overloaded with men, he had to save himself by swimming to another. But, severe as was the loss suffered, it was amply compensated by the recovery of the lighthouse-island, which along with the mole as far as the first arch-opening remained in the hands of Caesar.
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Reference address : https://www.ellopos.net/elpenor/rome/5-10-brundisium-pharsalus-thapsus.asp?pg=105