Second Punic War in 217. Moving to southern Italy in 216, Hannibal at Cannae annihilated the largest army the Romans had ever assembled. After the death or imprisonment of 130,000 Roman troops in two years, 40% of Rome's Italian allies defected to Carthage, giving her control over most of southern Italy. Macedon and Syracuse joined the Carthaginian side after Cannae and the conflict spread to Greece and Sicily. From 215–210 the Carthaginian army and navy launched repeated amphibious assaults to capture Roman Sicily and Sardinia but were ultimately repulsed. Against Hannibal's skill on the battlefield, the Romans adopted the Fabian strategy – the
Socii to raise a double-strength army of four legions and four "alae" e.g. at the Battle of Cannae in 216 BC, where each Consul commanded an army of about 40,000 men. Polybius states that the Romans and their allies could draw on a grand total of 770,000 men fit to bear arms (of which 70,000 met the property requirement for cavalry) in 225 BC, shortly before the start of the Second Punic War. The Romans reportedly asked their allies for an urgent register of all "men fit to bear arms" for a "tumultus Gallicus". Polybius' subtotals, however, are garbled, as he