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
Retreat of the Pompeians from Ilerda
The supplies of the Pompeians were now rendered scarce through the foraging parties of Caesar and the defection of the neighbouring communities; they resolved at length to retire behind the line of the Ebro, and set themselves in all haste to form a bridge of boats over the Ebro below the mouth of the Sicoris. Caesar sought to cut off the retreat of his opponents over the Ebro and to detain them in Ilerda; but so long as the enemy remained in possession of the bridge at Ilerda and he had control of neither ford nor bridge there, he could not distribute his army over both banks of the river and could not invest Ilerda.
His soldiers therefore worked day and night to lower the depth of the river by means of canals drawing off the water, so that the infantry could wade through it. But the preparations of the Pompeians to pass the Ebro were sooner finished than the arrangements of the Caesarians for investing Ilerda; when the former after finishing the bridge of boats began their march towards the Ebro along the left bank of the Sicoris, the canals of the Caesarians seemed to the general not yet far enough advanced to make the ford available for the infantry; he ordered only his cavalry to pass the stream and, by clinging to the rear of the enemy, at least to detain and harass them.
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Reference address : https://www.ellopos.net/elpenor/rome/5-10-brundisium-pharsalus-thapsus.asp?pg=40