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
Among its captains Marcus Varro indeed was simply a celebrated scholar and a faithful partisan; but Lucius Afranius had fought with distinction in the east and in the Alps, and Marcus Petreius, the conqueror of Catilina, was an officer as dauntless as he was able. While in the Further province Caesar had still various adherents from the time of his governorship there,(18) the more important province of the Ebrowas attached by all the ties of veneration and gratitude to the celebrated general, who twenty years before had held the command in it during the Sertorian war, and after the termination of that war had organized it anew.
18. Cf. V. VII. Caesar in Spain
Pompeius could evidently after the Italian disaster do nothing better than proceed to Spain with the saved remnant of his army, and then at the head of his whole force advance to meet Caesar. But unfortunately he had, in the hope of being able still to save the troops that were in Corfinium, tarried in Apuli so long that he was compelled to choose the nearer Brundisium as his place of embarkation instead of the Campanian ports. Why, master as he was of the sea and Sicily, he did not subsequently revert to his original plan, cannot be determined; whether it was that perhaps the aristocracy after their short-sighted and distrustful fashion showed no desire to entrust themselves to the Spanish troops and the Spanish population, it is enough to say that Pompeius remained in the east, and Caesar had the option of directing his first attack either against the army which was being organized in Greece under Pompeius' own command, or against that which was ready for battle under his lieutenants in Spain. He had decided in favour of the latter course, and, as soon as the Italian campaign ended, had taken measures to collect on the lower Rhone nine of his best legions, as also 6000 cavalry-- partly men individually picked out by Caesar in the Celtic cantons, partly German mercenaries--and a number of Iberian and Ligurian archers.
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Reference address : https://www.ellopos.net/elpenor/rome/5-10-brundisium-pharsalus-thapsus.asp?pg=35