Known in ancient times as Dertona, the city was probably the oldest colony under Roman rule in the westernmost section of the Valley of the Po, on the road leading from Genua (Genoa) to Placentia (Piacenza). The city was founded c. 123–118 BC at the junction of the great roads; the Via Postumia and the Via Aemilia Scauri which merged to become the Via Julia Augusta. The site made Dertona an important military station under the Romans. Strabo speaks of it as one of the most considerable towns in this part of Italy, and from Pliny wrote that it was a Roman colony. Velleius mentions it among those founded under the Republic, it appears to have been recolonised under Augustus, from whence we find it bearing in inscriptions the title of "Julia Dertona". The assassin of Caesar, Brutus, encamped at Dertona on his march in pursuit of Mark Antony, after the Battle of Mutina, and it was one of the places where a body of troops was usually stationed during the later ages of the empire.