In the war with Hannibal, they were among the first to declare in his favour after the battle of Cannae, and it was in their country that Hannibal held his ground during the last stage of the war (at Castrum Hannibalis on the gulf of Scylacium).
After the battle of Cannae Crotona revolted from Rome, and Hannibal made it his winter quarters for three years.
Accordingly recourse is had, tinder the direction of the Sibylline books, to new forms of appeal for the divine help, the general vowing of the ver sacrum and the elaborate Greek lectisternium after Trasimene in 217 B.C., and the human sacrifice in the forum after Cannae in the following year.
The town came voluntarily under Roman sovereignty in 318 B.C., afforded a refuge to the Roman fugitives after Cannae, and remained faithful for the rest of the war.
Its importance was maintained, however, by its trade in agricultural products and in Apulian wool (which was there dyed and cleaned), by its port (probably Cannae) at the mouth of the Aufidus, and by its position on the high-road.
He took an active part in the subjugation of the Gauls in the north of Italy (225), and after the battle of Cannae (216) was employed by the Romans to proceed to Delphi in order to consult the oracle of Apollo.
As a protection against the Samnites Arpi became an ally of Rome, and remained faithful until after the battle of Cannae, but Fabius captured it in 213 B.C., and it never recovered its former importance.
In its lower course it flows near Canosa and traverses the celebrated battlefield of Cannae.