Roman army of the mid-Republic

The Roman army of the mid-Republic, also called the manipular or Polybian army, was the armed force fielded by the Roman Republic from the end of the Samnite Wars in 290 BC to the end of the Social War in 88 BC. Its defining feature was the manipular battle line: in place of a single phalanx, the Romans drew up in three lines of small maniples of 120 men, arranged in chessboard fashion for greater flexibility. Each legion was usually accompanied by a non-citizen formation of similar size, the ala, drawn from Rome's Italian allies. Mercenaries with specialist skills were added during the Second Punic War, and by about 100 BC cohorts had replaced maniples as the basic tactical unit. Its early phase is described in detail by the historian Polybius.