The war had commenced in 264 BC with Carthage in control of much of Sicily, where most of the fighting took place. In 256–255 BC the Romans attempted to strike at the city of Carthage in North Africa, but suffered a heavy defeat by a Carthaginian army strong in cavalry and elephants. When the focus of the war returned to Sicily, the Romans captured the large and important city of Panormus in 254 BC. Thereafter they avoided battle for fear of the war elephants which the Carthaginians had shipped to Sicily. In late summer 250 BC Hasdrubal led out his army to devastate the crops of the cities of Rome's allies. The Romans withdrew to Panormus and Hasdrubal pressed on to the city walls.