The Carthaginians suffered a wave of defections of local Celtiberian tribes to Rome. The Roman commanders captured Saguntum in 212 BCE and in 211 BCE hired 20,000 Celtiberian mercenaries to reinforce their army. Observing that the three Carthaginian armies were deployed apart from each other, the Romans split their forces. This strategy resulted in the battle of Castulo and the battle of Ilorca, usually referred to jointly as the battle of the Upper Baetis. Both battles ended in complete defeat for the Romans, as Hasdrubal had bribed the Romans' mercenaries to desert.

The Roman fugitives fled north of the Ebro, where they eventually gathered a hodge-podge army of 8,000–9,000 soldiers. The Carthaginian commanders made no coordinated attempts to wipe out these survivors and then send help to Hannibal. In late 211 BCE, Rome sent 13,100 troops under Claudius Nero to reinforce its forces in Iberia. Neither did Nero score any spectacular victories nor the Carthaginians launch any coordinated assault on the Romans in Iberia. With the Carthaginian armies in Iberia failing to eliminate the Romans, Hannibal would not get any reinforcements from Iberia during the crucial year of 211 BCE, when the Romans were besieging Capua.