During the next winter, Mago gathered a new army that he wanted to transfer to Italy, for an all-out attack on its capital Rome. However, his brother Hasdrubal was defeated near Ilerda, close to the mouth of the river Ebro, by the Romans, who understood that Hannibal could not be defeated, but reasoned that it might be possible to cut him off from his base in Spain. They had sent Gnaeus and Publius Cornelius Scipio, who had overcome Hasdrubal; in the spring of 215, Mago was sent out to Spain to help this brother.
However, successes were rare, until a third force was sent to Spain, commanded by Hasdrubal, son of Gesco. The three Carthaginian armies defeated and killed the two Roman commanders in 211. At that moment, the best course would have been to lead one, two or all armies out of Spain to Italy, but the three commanders were on bad terms, and failed to exploit their victory.In 209, it was too late. Hasdrubal Barca was in Central Spain; Hasdrubal, son of Gesco, near the mouth of the river Tagus; and Mago near Gibraltar. Unexpectedly, the Roman commander Publius Cornelius Scipio, the son of the man who had been killed in 211, captured the Carthaginian capital in Spain, New Carthage (modern Cartagena).
To the Carthaginians, this was a terrible loss, from which they never recovered. In 208, Hasdrubal Barca was defeated by Scipio, and although the Carthaginian commander was able to regroup his army, cross the Pyrenees and invade Italy, Spain was forever lost. Mago, left as supreme commander, was unable to restore the Carthaginian fortunes. He conscripted soldiers in Central Spain, northern Africa, and the Baleares, but was unable to defend Andalusia. The Carthaginians were defeated at Ilipa, and Mago contracted all remaining forces in Gades (modern Cadiz).
In the autumn of 206, he was ordered by the Carthaginian Senate to leave Spain and support Hannibal. He spent the winter at the Balearic island Menorca, and invaded Liguria in northern Italy in the spring. Several Etrurian towns wanted to side with him, but he was unable to support them. In 203, he and Hannibal were recalled to Carthage, because Scipio (who had been consul and governor of Sicily in the meantime) had invaded Africa, which now needed protection.
It is unclear what happened next. Several sources (e.g., the Roman historian Livy) maintain that Mago obeyed his superiors, but was wounded and died when he had reached Sardinia. Others, however, state that he did not obey and continued the war from Liguria after Scipio had defeated Hannibal at Zama (202). If this is true, he surrendered not until the peace treaty had been signed, survived the end of the war, and may have died as late as 193.
Mago Barca lives on in a most surprising way. On Menorca, he had founded the city that is still called Port Mahon. The typical local egg sauce that has conquered the world is known as mayonnaise.