Punic War is missing after 216 BC or only exists in fragmentary form. As a result, the main source for much of the war is the account written by the Roman historian Livy. This is commonly used by modern historians where Polybius's account is not extant. Livy relied heavily on Polybius, but wrote in a more structured way, with more details about Roman politics; he was also openly pro-Roman. His accounts of military encounters are often demonstrably inaccurate; the classicist Adrian Goldsworthy says Livy's "reliability is often suspect", and the historian Phillip Sabin refers to Livy's "military ignorance". Other, later, ancient histories of the war exist, although often in fragmentary or summary form. Modern historians usually take into account the writings of Diodorus Siculus and Cassius Dio, two Greek authors writing during the Roman era; they are described by John Lazenby as "clearly far inferior" to Livy, but some fragments of Polybius can be recovered from their texts. The Greek moralist Plutarch wrote several biographies of Roman commanders in his Parallel Lives. Other sources include coins, inscriptions, archaeological evidence and empirical evidence from reconstructions. Opposing forces Most male Roman citizens were eligible for military service and would serve as infantry, the wealthier equites providing a cavalry component. Traditionally, when at war the Romans would raise four legions, each of 4,200 infantry and 300 cavalry. Approximately 1,200 of the infantry, poorer or younger men unable to afford the armour and equipment of a standard legionary, served as javelin-armed skirmishers, known as velites. They carried several javelins, which would be thrown from a distance, a short sword and a shield. The rest were equipped as heavy infantry, with body armour, a large shield and short thrusting swords. They were divided into three ranks: the front rank also carried two javelins, while the second and third ranks were equipped with a thrusting spear instead. Legionary sub-units and individual legionaries both fought in relatively open order. It was the long-standing Roman procedure to elect two men each year as senior magistrates, known as consuls, who in time of war would each lead an army. An army was usually formed by combining two Roman legions with a similarly sized and equipped pair of legions provided by their Latin allies; these legions usually had a larger attached complement of cavalry than Roman ones. Carthaginian citizens only served in their army if there was a direct threat