Ala (Roman allied military unit)

When the Roman armies started being composed partly of Roman citizens and partly of socii (allies from the rest of the Italian mainland), either Latini or Italici, it became the practice to marshal the Roman troops in the centre of the battle line and the socii upon the wings. Consular armies of the mid-Republic would consist of two legions of Roman citizens and two legions of "ala", with the ala supplying thirty turmae of cavalry per legion, whereas the Roman provided only ten turmae. Hence ala and alarii denoted the contingent furnished by the allies, both horse and foot, and the two divisions were distinguished as dextera ala (right wing) and sinistra ala (left wing).[2]

As late as Polybius' times, contingents of allies forming the alae were recruited by their own leaders in their homelands, which were expected to levy an equivalent number to the Roman troops; the specifications of those agreements were covered in the formula togatorum.[1] They were managed by six Roman officers called praefecti sociorum, equivalent to the legion's six military tribunes, who were chosen from the equestrian order by the consul at charge[1] However, Rome would also trust on their allied commander themselves, with outstanding examples like the Frentani Oblacus Volsinius or the Campanian Decius Vibellius during the Pyrrhic War.[3]

Socii were expected to fight in the same manner and equipment as the Roman troops and provide their own basic rations, and were in turn would receive a percentage of any loot gained, although at a lower rate than their Roman equivalents.[1]