Despite the defeat of their invasion of Punic North Africa in 255 B.C. (First Punic War), and the loss of their fleet in a storm in the same year, in 254 B.C. the Romans decided to take the initiative. Their target would be Panormus (modern Palermo), an important Carthaginian base on the northern coast of Sicily. First they needed to replace the fleet lost as sea in the previous year. According to Polybius they constructed a fleet of 220 ships in only three months. Despite the heavy losses of the previous year, they were also able to raise 80,000 men to man those ships.
Under the command of the two Consuls for the year, Aulus Calatinus and Cornelius Asina, the Romans landed an army close to Panormus, and besieged it from land and sea.
The city had two districts, the outer New Town and inner Old Town. Eight years earlier, at Agrigentum, the Romans appeared to have been content to simply starve out their enemies. Now they were better prepared for siege work. According to Polybius they built siege works at two places, then used their battering rams to create a breach in the walls of the New Town by destroying a tower on the sea side of the walls.
With the Romans inside the city, the defenders of the Old Town negotiated terms of surrender. According to Diodorus the wealthier inhabitants were allowed to buy their safety for 200 drachmas. 13,000 people who could not afford that amount were taken as captives.
For the rest of the war Panormus was an important base for the Roman armies on Sicily. At the end of the war it was given its independence, and not placed under any obligations to Rome, a very generous settlement. After the Roman capture of Panormus a number of other cities in eastern Sicily changed sides, expelling Carthaginian garrisons. It has been suggested that Carthage was holding hostages from those cities in Panormus, and that they were freed by the Romans. That explanation is probably over elaborate for cities such as Solus, only a few miles east of Panormus. The replacement of a Punic stronghold by a Roman one would surely have been enough to convince the inhabitants of many neighbouring cities to change sides.
In the aftermath of the loss of Panormus, Carthaginian territory on Sicily was reduced to a narrow strip of land along the west coast, with strong points at Lilybaeum and Drepana. However, rather than attempt to capture these cities, the Romans decided to launch another expedition to Africa, this time hoping to gain support in Libya. The failure of this expedition (253 B.C.) and the loss of yet another fleet in a storm discouraged the Romans, who temporarily abandoned their attempts to maintain a powerful fleet. The last Carthaginian outposts on Sicily would not be captured until 242 B.C.