Hannibal's son Hanno, the subject of this article, was on Sicily when the war broke out, and did his best to help his father. First, he fortified Acragas in the south of Sicily, converting an allied city into a Carthaginian stronghold. Then, he marched on Messana, supported by king Hiero II of Syracuse. Hanno was forced to retreat after Roman successes in the west (263), and could not prevent that Hiero switched sides.
Meanwhile, his father had garrisoned Acragas, and in the summer of 262, the two Roman consuls Lucius Postumius Megellus and Quintus Mamilius Vitulus laid siege to the city. Hannibal sent message after message to Carthage to ask for reinforcements.
In the fifth month, they arrived, led by Hanno. He immediately captured the Roman supply base, won a cavalry engagement, and built his camp near the Roman siege walls. Two months passed with inconclusive skirmishing, but then, Hanno risked an open battle, which he lost. He was forced to leave the theater of operations (January 261). During the night, Hannibal, benefiting from Roman euphoria, broke away from Acragas, which was captured the next day by the Romans. Its inhabitants were sold into slavery.
Hanno returned to Carthage, where he was fined (he had to pay 6,000 gold pieces). At the same time, his father was defeated in a naval engagement off Mylae (story). Yet, in 258, he and Hannibal were in active service again, fighting near Sardinia. The son was more successful than his father, who was defeated by the Romans and crucified by his own soldiers.
In the meantime, the Romans had decided to invade Africa. Their consul Marcus Atilius Regulus built a large navy (330 ships according to Polybius of Megalopolisnote[Polybius, World History 1.25.7.] and defeated the Carthaginian fleet of Hanno and Hamilcar (350 ships) at Ecnomus, near modern Licata. Almost 290,000 soldiers had been involved in what was probably the largest battle in Antiquity.
Hanno was not blamed for the disaster. He was sent to the Romans to negotiate a peace treaty, although this maneuver was regarded as an attempt to gain time. Not much later, Regulus landed in Africa at a place called Shield (Clupea or Aspis), and Hanno was one of the commanders sent out to fight against him; the main commander, however, was Hasdrubal and, later, a Greek mercenary named Xanthippus, who defeated the expeditionary army. After this, Hanno disappears from our sources.