Doing battle with barbarians was very different from engaging the disciplined army of a state like Macedonia. Formal combat, in which he would confront the entire enemy host was not something Aulus expected, despite their numerical superiority. His informants confirmed that the Celt-Iberians, at his approach, had withdrawn from the coastal plain and taken to the hills. This underlined his belief that it would be a war of ambush and raid. He had set himself for a difficult task, with his legions broken up, operating in centuries and cohorts, trying to destroy the means by which the rebels sustained themselves. They would need to be ruthless and cruel, burning villages and destroying pasture and crops, taking hostages and enslaving women and children if the insurrection was to be brought under control. He in turn would need to be tough, to prevent his troops from descending into a rabble, if required, killing some to maintain discipline. Necessary in Macedonia, such measures, in Spain, would be even more indispensable.

That whispering slave who had stood behind him had been right! It was foolish to assume anything in war, to be so sure that his enemies would wait in the hills for him to attack, just as it was unwise to rely upon his reputation to fight his battles for him. His name meant little to the Celt-Iberians and nothing to this Brennos, who was clever, and more powerful than the Romans had imagined. Somehow he had achieved what they thought impossible, the welding together of the notoriously cantankerous Celts into a single fighting unit. He had no intention of leaving Aulus to march peacefully to his base camp, appearing suddenly at the head of a multitude of braying tribesmen to attack an army that had not even begun to pursue him, an army strung out on the march.

By their disordered tactics, really just a melee in which those who could engage did so, the Celt-Iberians had managed to split his forces, separating the auxiliary legions from the Roman troops.