Suddenly one evening, after the two armies had already encamped and the bivouac fires were kindled, the Celtic infantry again broke up and retreated on the road towards Faesulae (Fiesole): the cavalry occupied the advanced posts during the night, and followed the main force next morning.

When the Tuscan militia, who had pitched their camp close upon the enemy, became aware of his departure, they imagined that the host had begun to disperse, and marched hastily in pursuit.

The Gauls had reckoned on this very result: their infantry, which had rested and was drawn up in order, awaited on a well-chosen battlefield the Roman militia, which came up from its forced march fatigued and disordered.

Six thousand men fell after a furious combat, and the rest of the militia, which had been compelled to seek refuge on a hill, would have perished, had not the consular army appeared just in time.

This induced the Gauls to return homeward.
Their dexterously-contrived plan for preventing the union of the two Roman armies and annihilating the weaker in detail, had only been partially successful; now it seemed to them advisable first of all to place in security their considerable booty.