Caesar’s risky move in crossing the Rubicon surprised his opponents. Pompey judged it unwise to fight Caesar in Italy and decided to withdraw to Greece and the east, where he was able to recruit a well-trained army. His allies fled Italian towns and cities as Caesar approached. Lucius Domitius Ahenobarbus was the only one who fought back. He dug in at Corfinium. But his own men mutinied and handed him over to his enemy together with other senators.

Caesar let them go free, knowing full well they would go back to Pompey—which they did. This magnanimous and unexpected gesture was calculated to show the public that he was no tyrant, but rather a man on the side of the people and the republic, an image he would foster until the end of his life.

In this map, the white line shows Caesar’s invasion route through Italy in 49 B.C., while the green line shows Pompey’s route. Black lines indicate detours made by Caesar’s troops.

After crossing the Rubicon into the Roman Republic near Ravenna in early January, Caesar marches his forces south to Ariminum. Pompey and his allies abandon Rome for Capua.

Caesar sends the tribune Mark Antony with five cohorts of the 13th Legion to occupy Arretium. He sends another three cohorts to the coastal cities of Pisaurum, Fanum Fortunae, and Ancona.

Caesar advances south, easily taking the cities of Pisaurum, Fanum, and Ancona. Some of his troops are dispatched west to the city of Iguvium; these forces easily take the city.

Cingulum opens its gates to Caesar’s troops without any bloodshed. Pompey’s garrison at Asculum leaves their post before the arrival of Caesar’s forces as they move down the coastline.

Caesar makes his camp in Apulia. His troops approach Sulmo, which immediately surrenders. Corfinium falls with the capture of three legions. Many of these soldiers join up with Caesar.

As Caesar advances with an ever growing army, Pompey abandons Capua for Brundisium. Caesar races to cut him off, but Pompey sails to the Greek shore with his troops in mid-March.