succeeded by his son-in-law, Hasdrubal, in 229BC and then his son, Hannibal, in 221BC. In 226BC the Ebro Treaty was agreed with Rome, specifying the Ebro River as the northern boundary of the Carthaginian sphere of influence. At some time during the next six years Rome made a separate agreement with the city of Saguntum, which was situated well south of the Ebro. In 219BC a Carthaginian army under Hannibal besieged Saguntum, and after eight months captured and sacked it. Rome complained to the Carthaginian government, sending an embassy to its senate with peremptory demands. When these were rejected Rome declared war in spring 218BC. Since the end of the First Punic War Rome had also been expanding, especially in the area of north Italy either side of the River Po known as Cisalpine Gaul. Roman attempts to establish towns and farms in the region from 232 BC led to repeated wars with the local Gallic tribes, who were finally defeated in 222. In 218 the Romans pushed even further north, establishing two new towns, or "colonies", on the Po and appropriating large areas of the best land. Most of the Gauls simmered with resentment at this intrusion. Italy Hannibal crosses the Alps, 218 BC During 218BC there was some naval skirmishing in the waters around Sicily; the Romans repulsed a Carthaginian attack and captured the island of Malta. In Cisalpine Gaul (modern northern Italy), the major Gallic tribes attacked the Roman colonies there, causing the settlers to flee to their previously established colony of Mutina (modern Modena), where they were besieged. A Roman relief force broke through the siege, but was then ambushed and itself besieged. An army had previously been raised by the Romans to campaign in Iberia, but the Roman Senate detached one Roman and one allied legion from it to send to north Italy. Recruiting fresh troops to replace these delayed the army's departure for Iberia until September. At the same time a Roman army in Sicily under the consul Sempronius Longus was preparing for an invasion of Africa. Meanwhile, Hannibal assembled a Carthaginian army in New Carthage (modern Cartagena) and led it northwards along the Iberian coast in May or June. It entered Gaul and took an inland route, to avoid the Roman allies to the south. At the battle of Rhone Crossing, Hannibal defeated a force of local Gauls which sought to bar his