authorised the raising of double-sized armies by Varro and Paullus, a force of 86,000 men, the largest in Roman history up to that point. Paullus and Varro marched southward to confront Hannibal and encamped away. Hannibal accepted battle on the open plain between the armies in the battle of Cannae. The Roman legions forced their way through Hannibal's deliberately weak centre, but Libyan heavy infantry on the wings swung around their advance, menacing their flanks. Hasdrubal Gisco led the Carthaginian cavalry on the left wing and routed the Roman cavalry opposite, then swept around the rear of the Romans to attack their cavalry on the other wing. The heavily outnumbered Carthaginian infantry held out until Hasdrubal charged into the legions from behind. As a result, the Roman infantry was surrounded with no means of escape. At least 67,500 Romans were killed or captured. Miles describes Cannae as "Rome's greatest military disaster". Toni Ñaco del Hoyo describes the Trebia, Lake Trasimene and Cannae as the three "great military calamities" suffered by the Romans in the first three years of the war. Brian Carey writes that these three defeats brought Rome to the brink of collapse. Within a few weeks of Cannae a Roman army of 25,000 was ambushed by Boii Gauls in Cisalpine Gaul at the battle of Silva Litana and annihilated. Fabius became consul in 215 BC and was re-elected in 214 BC. Roman allies defect, 216–214 BC Little has survived of Polybius's account of Hannibal's army in Italy after Cannae. Livy gives a fuller record, but according to Goldsworthy "his reliability is often suspect", especially with regard to his descriptions of battles; many modern historians agree, but nevertheless his is the best surviving source for this part of the war. Several of the city states in southern Italy allied with Hannibal, or were captured when pro-Carthaginian factions betrayed their defences. These included the large city of Capua and the major port city of Tarentum (modern Taranto). Two of the major Samnite tribes also joined the Carthaginian cause. By 214BC the bulk of southern Italy had turned against Rome, although there were many exceptions and the majority of Rome's allies in central Italy remained loyal. All except the smallest towns were too well fortified for Hannibal to take by assault, and blockade could be a long-drawn-out affair, or if the target was a port, impossible. Carthage's new allies felt little