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 war-vessels, which Caesar had given orders to build in the Gallic, Sicilian, and Italian ports, were not yet ready or at any rate not on the spot; his squadron in the Adriatic had been in the previous year destroyed at Curicta;(27) he found at Brundisium not more than twelve ships of war and scarcely transports enough to convey over at once the third part of his army--of twelve legions and 10,000 cavalry--destined for Greece.
27. Cf. V. X. Caesar's Fleet and Army in Illyricum Destroyed
The considerable fleet of the enemy exclusively commanded the Adriatic and especially all the harbours of the mainland and islands on its eastern coast. Under such circumstances the question presents itself, why Caesar did not instead of the maritime route choose the land route through Illyria, which relieved him from all the perils threatened by the fleet and besides was shorter for his troops, who mostly came from Gaul, than the route by Brundisium. It is true that the regions of Illyria were rugged and poor beyond description; but they were traversed by other armies not long afterwards, and this obstacle can hardly have appeared insurmountable to the conqueror of Gaul. Perhaps he apprehended that during the troublesome march through Illyria Pompeius might convey his whole force over the Adriatic, whereby their parts might come at once to be changed--with Caesar in Macedonia, and Pompeius in Italy; although such a rapid change was scarcely to be expected from his slow-moving antagonist.
Perhaps Caesar had decided for the maritime route on the supposition that his fleet would meanwhile be brought into a condition to command respect, and, when after his return from Spain he became aware of the true state of things in the Adriatic, it might be too late to change the plan of campaign. Perhaps-- and, in accordance with Caesar's quick temperament always urging him to decision, we may even say in all probability--he found himself irresistibly tempted by the circumstance that the Epirot coast was still at the moment unoccupied but would certainly be covered in a few days by the enemy, to thwart once more by a bold stroke the whole plan of his antagonist.
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Reference address : https://www.ellopos.net/elpenor/rome/5-10-brundisium-pharsalus-thapsus.asp?pg=66