The Scipios, who during the absence of the enemy's general (541, 542) had continued to plunder and to gain partisans in the Carthaginian territory, found themselves unexpectedly assailed by forces so superior that they were under the necessity of either retreating behind the Ebro or calling out the Spaniards.

They chose the latter course, and took into their pay 20,000 Celtiberians; and then, in order the better to encounter the three armies of the enemy under Hasdrubal Barcas, Hasdrubal the son of Gisgo, and Mago, they divided their army and did not even keep their Roman troops together.

They thus prepared the way for their own destruction.
While Gnaeus with his corps, containing a third of the Roman and all the Spanish troops, lay encamped opposite to Hasdrubal Barcas, the latter had no difficulty in inducing the Spaniards in the Roman army by means of a sum of money to withdraw--which perhaps to their free- lance ideas of morals did not even seem a breach of fidelity, seeing that they did not pass over to the enemies of their paymaster.
Nothing was left to the Roman general but hastily to begin his retreat, in which the enemy closely followed him.

Meanwhile the second Roman corps under Publius found itself vigorously assailed by the two other Phoenician armies under Hasdrubal son of Gisgo and Mago, and the daring squadrons of Massinissa's horse gave to the Carthaginians a decided advantage.

The Roman camp was almost surrounded; when the Spanish auxiliaries already on the way should arrive, the Romans would be completely hemmed in.