Extraordinarii The Extraordinarii were the elite troops of the Roman alae , recruited from the Socii , Rome ' s Italian military allies . The name refers to their nature ; i . e . , " extraordinary " or " chosen " men . Recruitment . Almost all the details we know of the extraordinarii are described to us in " The Histories " of the ancient Greek historian Polybius . A standard Consular army of the Republic was made up of two legions and an comparable amount of Italian allied troops , termed the alae . In theory , the alae would number the same as the legions , except for the cavalry which was doubled ; so a standard alae would contain about 1800 cavalry and 8400 foot . In practice , there were often more allied infantry than Romans ; for instance , the 4 legions ( numbering 15000 roman infantry ) was supported by 20 , 000 allied infantry at the Battle of the Trebia . Similar discrepancies can be found in other Roman battles of the era . From the whole force of the alae , the Consul would request the Praefecti Sociorum ( commanders of the allied forces ) to select for the extraordinarii about a third of the cavalry ( the " equites extraordinarii " ) and a fifth of the infantry ( the " pedites extraordinarii " ) of those men best fitted for service . The extraordinarii for a standard consular army as described by Polybius would thus number 600 cavalry and 1680 infantry . Like the rest of the alae , the extraordinarii are divided into cohort s and turmae . Usage . On the march , the Extraordinarii had the dangerous privilege of leading the army , though they could also be used as a rearguard if the army was threatened from that direction . They would also be used for other dangerous tasks such as pickets and reconnaissance . In camp , the extraordinarii had their tents in the command section of the roman army camp , just behind the tents of the Tribune . The equites extraordinarii were camped closest to the command tents , along with the household troops of the Consul ( i . e . , volunteers ) ; while the pedites extraordinarii were camped behind them closes to the camp walls . History . It is uncertain when the selection of extraordinarii started . Franz Fröhlich , in his work on the Guard troops of the Roman Republic , speculates that they were created shortly after the Latin War which ended in 338 BC . Livy mentions " delectae cohortes " ( chosen cohorts ) of the Socii in an episode as early as 310 BC ; this is assumed to be the first mention of the extraordinarii . Livy ' s description of the campaign leading up to the Battle of Sentinum in 295 BC also references both Campanian " equites delecti " as well as the use of allied troops to defend against an assault on the headquarter tents of a Roman camp , consistent with the description of the camp layout given by Polybius . Polybius , writing after 146 BC , describes the extraordinarii in detail as referenced above , though there are few mentions of these troops in other sources at this time . The formation was presumably phased out with the so - called Marian reform s when the separation between citizen legions and alae was abolished . There is no mention in the sources of the extraordinarii after the Social War .