Seventy thousand Samnites, Etruscans, Umbrians, Campanians, and Romans joined forces to meet the common threat that faced them to the North.

Roughly a quarter of this huge force was called up for active service, while the rest was employed in garrison duty, or held back in reserve.

The other consul, Lucius Aemilius Papus, with a full consular army, took up position at Ariminum, to guard the eastern coast route.

The Gauls then fell back toward Faesulae, leaving their cavalry to cover their retreat, and the Roman general, pursuing them incautiously, allowed himself to be drawn into an ambush and suffered a grave defeat.

The Roman force was only saved from total destruction by the arrival of Aemilius Papus, who had left his position at Ariminum as soon as he learned that the Gauls were on the march to Rome.