Battle of Cannae shaping the military structure and tactical organization of the Roman Republican army. At Cannae, the Roman infantry assumed a formation similar to the Greek phalanx. This left them vulnerable to Hannibal's tactic of double envelopment since their inability to maneuver independently from the mass of the army made it impossible for them to counter the strategic encirclement used by the Carthaginian cavalry. The laws of the Roman state requiring command to alternate between the two consuls restricted strategic consistency. In the years following Cannae, striking reforms were introduced to address these deficiencies. First, the Romans "articulated the phalanx, then divided
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