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 Allobroges which sought to bar his way. A Roman fleet carrying the Iberian-bound army landed at Rome's ally Massalia (modern Marseille) at the mouth of the Rhone, but Hannibal evaded the Romans and they continued to Iberia. The Carthaginians reached the foot of the Alps by late autumn and crossed them, surmounting the difficulties of climate, terrain and the guerrilla tactics of the native tribes. Hannibal arrived with 20,000 infantry, 6,000 cavalry, and an unknown number of elephantsthe survivors of the 37 with which he left Iberiain what is now Piedmont, northern Italy. The Romans were still in their winter quarters. His surprise entry into the Italian peninsula led to the cancellation of Rome's planned campaign for the year: an invasion of Africa.