Claudius Nero quickly reached Marcus Livius, who was camped at Sena along with the praetor Porcius Licinius. Hasdrubal was camped approximately a half-mile to the north. Because Claudius Nero had conveniently arrived at night, his presence was not detected until the next day, when the Romans drew themselves up for battle. Hasdrubal drew his army up as well, but upon closer observation of the forces assembled before him, noticed that Marcus Livius' army seemed to have grown considerably over the course of the night, and that he had a much larger contingent of cavalry. Hasdrubal remembered hearing a trumpet in the Roman camp heralding the arrival of an important figure the night before—a sound he had become familiar with during his entanglements with the Romans in Hispania—and correctly concluded that he was now facing two Roman armies. Fearing defeat, he retreated from the field.