Among republicans like Cicero, whose correspondence traces day by day the news of Caesar's siege of Corfinium, Pompey's refusal to march north to help Domitius and his forces was a source of shame adding to the indictment of the general's cowardice in fleeing from Rome and, within two months, from Italy itself (for an exact timetable of events, letters and despatches from Pompey and Domitius, see D. R. Shackleton Bailey, Cicero Ad Atticum IV app. 4, 448–59).

But Pompey's military despatches have enabled historians, notably C. Veith (‘Corfinium: Eine kriegsgeschichtliche Studie’, Klio 13, (1913) 1–22) to reconstruct a different picture. As Caesar marched south across the eastern foothills of the Apennines, many communities went over to him, and the Pompeian garrisons could not retain the loyalty of the townsfolk. Domitius, armed with his official appointment as proconsul of Gaul, had gone to his local territory among the Marsi and Paeligni and drafted fifteen to twenty cohorts which he concentrated on Corfinium, a well-fortified town on a high plateau, 39 kilometres south of the Gran Sasso, the steepest ridge of the Appennine range (cf. 2.396–8). He may have thought it was defensible, since a strong river, the Aternus, flowed between Corfinium and Caesar's approaching force, but as first Asculum then Cingulum in Pompey's own region declared for Caesar and expelled their garrisons, Domitius must have grown nervous.