The Roman army of the mid-Republic, also called the manipular Roman army or the Polybian army, refers to the armed forces deployed by the mid-Roman Republic, from the end of the Samnite Wars (290 BC) to the end of the Social War (88 BC). The first phase of this army, in its manipular structure (290–c. 130 BC), is described in detail in the Histories of the ancient Greek historian Polybius, writing before 146 BC.
The central feature of the mid-Republican army was the manipular organisation of its battle line. Instead of a single, large mass (the phalanx) as in the Early Roman army, the Romans now drew up in three lines () consisting of small units (maniples) of 120 men, arrayed in chessboard fashion, giving much greater tactical strength and flexibility. This structure was probably introduced in c. 300 BC during the Samnite Wars. Also probably dating from this period was the regular accompaniment of each legion by a non-citizen formation of roughly equal size, the ala, recruited from Rome's Italian allies, or . The latter were about 150 autonomous states which were bound by a treaty of perpetual military alliance with Rome. Their sole obligation was to supply to the Roman army, on demand, a number of fully equipped troops up to a specified maximum each year. Evidence from Roman army camps near Numantia in Spain suggests that a much larger tactical unit, the cohort (480 men, equivalent to 4 maniples) already existed, alongside maniples, in the period 153–133 BC. By c. 100 BC, cohorts appear to have fully replaced maniples as the basic tactical unit.
The Second Punic War (218–201 BC) saw the addition of a third element to the existing dual Roman/Italian structure: non-Italian mercenaries with specialist skills lacking in the legions and : Numidian light cavalry, Cretan archers, and Balearic slingers. From this time, these units always accompanied Roman armies.
The Republican army of this period, like its earlier forebear, did not maintain standing or professional military forces, but levied them, by compulsory conscription, as required for each campaigning season and disbanded thereafter (although formations could be kept in being over winter during major wars). Service in the legions was limited to property-owning Roman citizens, normally those known as (age 16–46). The army's senior officers, including its commanders-in-chief, the Roman consuls, were all elected annually at the People's Assembly. Only members of the Roman equestrian order—the —were eligible to serve as senior officers. of the highest social classes ( and the First Class of commoners) provided the legion's cavalry, the other classes the legionary infantry. The (the lowest and most numerous social class, assessed at under 400 wealth in c. 216 BC) were until c. 200 BC ineligible for legionary service and were assigned to the fleets as oarsmen. Elders, vagrants, freedmen, slaves and convicts were excluded from the military levy, save in emergencies. During a prolonged such emergency, the Second Punic War, severe manpower shortages necessitated that the property requirement be ignored and large numbers of proletarii conscripted into the legions. After the end of this war, it appears that were admitted to the legions as volunteers (as opposed to conscripts) and at the same time the property requirement was reduced to a nominal level by 150 BC, and finally scrapped in the consulship of Gaius Marius (107 BC).
The legionary cavalry also changed, probably around 300 BC onwards from the light, unarmoured horse of the early army to a heavy force with metal armour (bronze cuirasses and, later, mail coats). Contrary to a long-held view, the cavalry of the mid-Republic was a highly effective force that generally prevailed against strong enemy cavalry forces (both Gallic and Greek) until it was decisively beaten by the Carthaginian general Hannibal's horsemen during the second Punic War. This was due to the greater operational flexibility Hannibal’s Numidian light cavalry allowed.
For the vast majority of the period of its existence, the Polybian levy was at war. This led to great strains on Roman and Italian manpower, but forged a superb fighting machine. During the Second Punic War, fully two-thirds of Roman were under arms continuously. In the period after the defeat of Carthage in 201 BC, the army was campaigning exclusively outside Italy, resulting in its men being away from their home plots of land for many years at a stretch. They were assuaged by the large amounts of booty that they shared after victories in the rich eastern theatre. But in Italy, the ever-increasing concentration of public lands in the hands of big landowners, and the consequent displacement of the soldiers' families, led to great unrest and demands for land redistribution. This was successfully achieved, but resulted in the disaffection of Rome's Italian allies, who as non-citizens were excluded from the redistribution. This led to the mass revolt of the and the Social War (91–88 BC). The result was the grant of Roman citizenship to all Italians and the end of the Polybian army's dual structure: the were abolished and the recruited into the legions. The Roman army of the late Republic (88–30 BC) resulted, a transitional phase to the Imperial Roman army (30 BC – AD 284).
Main sources
As can be deduced from its "Polybian" epithet, the most important extant literary source on the Roman army of this period are The Histories of the Greek historian Polybius, published in c. 160 BC. The surviving chapters cover the First and Second Punic Wars. Chapter VI contains a detailed analysis of the organisation and basic practices of the army. Polybius is generally seen by modern historians as a reliable and balanced source, but there are some inconsistencies and unclear points of detail in his account. These partly derive from his use of Greek terms to describe Roman military units and other terms. Moreover, the chronology of his account is uncertain. It has been suggested, from features such as joint consular armies, that he describes the army as it was c. 218 BC, at the start of the Second Punic War, considerably earlier than his time of writing (c. 160 BC).Dobson (2008) 407 It is also possible that his account contains details from various historical periods. Polybius' source for Chapter VI remains uncertain. It has been suggested he was using an old army manual. The second most important literary source is Ab urbe condita, a massive history of Rome published in c. AD 20, by the Augustan-era Roman historian Livy, whose surviving books XXI–XLV cover the years 218–168 BC. Although a narrative history lacking a specific analysis of the army as in Polybius, Livy's work contains much incidental information about the army and its tactics. Also useful are the monograph on the Jugurthine War by Sallust (published c. 90 BC) and the much later biographies of Roman leaders of the Republican period by Plutarch.
Unlike for the later Imperial Roman army, relatively little epigraphic evidence and pictorial evidence survives for army of this period. The most important bas relief is that on the tomb of Ahenobarbus (c. 122 BC), which provides the clearest and most detailed depiction of the equipment of mid-Republican officers and soldiers. The soldiers it depicts are: one senior officer, four infantrymen, and one cavalryman. Otherwise, there is a lack of tombstones showing soldiers in military dress as are common from the Principate era. The earliest such, dating from 42 BC, is the Padova Centurion.Bishop & Coulston (2006)
Published evidence from archaeological excavation is also far less abundant than for the imperial era, although it is growing rapidly. A critical corpus is from Roman fortified camps built around Numantia during campaigns in Iberia, including the Numantine Wars in Spain (155–133 BC). The most important excavated sites are the camps at Renieblas, which range in date from 195 to 75 BC. Of these, camp III dates from the 153 BC campaign of consul Quintus Fulvius Nobilior. The Castillejo camp was occupied in 137 by Gaius Hostilius Mancinus and again by Scipio Aemilianus in 134–133 BC. A further site at Peña Redonda is notable.Bishop & Coulston (2006) 48 These sites, and others, have yielded both information of camp layout and finds of military and other equipment. This large sequence of sites was excavated in 1905–12 by Adolf Schulten, who interpreted the results as being consistent with Polybius' detailed account of the design of Roman camps.Polybius VI.27–33 However, a reassessment (2008) of the data (including the results of later excavation of the sites) by Michael Dobson has concluded that the Numantia data only partially supports Polybius and suggests that troops were already partially organised in cohorts.Dobson (2008) Conclusions
Of major importance in our understanding of mid-Republican military equipment is the hoard of some 160 Roman weapons at Šmihel in Slovenia (known to the Romans as western Pannonia), dating from the period 200–150 BC. This site was along the major Roman route from Aquileia to Emona (Ljubliana). Originally unearthed in 1890, these finds were not fully published until around AD 2000. They include one helmet, four swords (two of them ), two spears, one hundred and six of various types, thirty-seven javelins, arrowheads and other miscellaneous items.
Background: The Roman–Italian military loose federation
The Roman/Italian military alliance had fully evolved by 264 BC and remained for 200 years the basis of Roman military organisation. From 338 BC to 88 BC Roman legions were invariably accompanied on campaign by an equal number of somewhat larger allied units called alae (literally: 'wings', as allied troops would always be posted on the flanks of the Roman battle line, with the Roman legions holding the centre). 75% of a normal consular army's cavalry was supplied by the Italian .
The alliance was distantly descended the Foedus Cassianum ('Treaty of Cassius', 493 BC) signed by the fledgling Roman Republic with its neighbouring Latin city-states shortly after the overthrow of the Roman monarchy in 510 BC. This was an indefinite military alliance with the other city-states of Old Latium, the home of the Latin tribe, to which the Romans themselves belonged. Although extant details are fragmentary, the treaty's basic features were a mutual non-aggression and defense pact, requiring all signatories to assist any of their number who was attacked with all their forces. It also appears to have provided for joint operations in the field, if such were decided upon at an annual conference. Judging by the provision that the Romans and Latins were to share booty on an equal basis, it is likely that the treaty required the Latins to contribute roughly the same number of troops to joint operations as Rome. It appears that command of any joint forces may have alternated between Romans and allies.Dionysius I The motive factor behind the alliance was the threat posed to the cities of Old Latium by the surrounding Italic hill tribes, notably the Volsci and Aequi, whose incursions intensified in this period. By 358 BC, however, the hill-tribe menace had receded and the Romans repudiated the . The succeeding period saw a steady increase in Roman encroachment in Old Latium.
In 341 BC, the Latin League, a confederation of the other city-states of Old Latium, went to war against Rome in an attempt to save what remained of their independence—the Latin War (341–338 BC). The Romans won a decisive victory and annexed most of Old Latium, unifying the Latin nation under their hegemony for the first time since the Tarquin era two centuries earlier.