The battle began with a fierce cavalry engagement on the flanks. Polybius described many of the Hispanic and Celtic horsemen facing the Romans dismounting due to the lack of space to fight on horseback, and called the struggle "barbaric" in the sense of its utter brutality. When the Carthaginian cavalry got the upper hand, they cut down their Roman opponents without giving quarter. On the other flank the Numidians engaged in a way that merely kept the Roman allied cavalry occupied. Hasdrubal kept his victorious Hispanic and Gallic cavalry under control and did not chase the retreating Roman right wing. Instead, he led them to the other side of the field to attack the socii cavalry still fighting the Numidians. Assailed from both sides, the allied cavalry broke before Hasdrubal could charge into contact and the Numidians pursued them off the field.