Roman army of the mid-Republic

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 alae: Numidian light cavalry, Cretan archers, and Balearic slingers.

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).

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).

[1] 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.

[6] 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.

This quasi-professional soldier volunteered in 200 BC and served a total of 22 years, reaching the rank of a senior centurion, but he owned a tiny plot of just one iugum (0.25 hectare) of land, only half the two iugera regarded as the equivalent of the minimum property qualification.

[18] The most recent analysis of archaeological data on the layout of successive army camps at Numantia in Spain suggests that cohorts were introduced gradually in the period from c. 140 BC and the process was probably complete by the time Marius was elected consul.

[25] Until 200 BC, the republican army, 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 them thereafter (although formations could be kept in being over winter, and for several years consecutively, during major wars).

After Rome acquired an overseas empire following the Punic Wars, armies stationed in key provinces became in effect standing forces, although no conscript could legally be required to serve more than six years consecutively.

Following the Punic Wars, proconsuls and propraetors served as the governors of the provinces of the overseas empire, in command of the military forces deployed there for a set term (normally three years).

[33] The duplication and rotation of command was a characteristic feature of the Roman Republic, which, from the time of the expulsion of the kings, had always aimed for collegiate offices, to avoid excessive concentration of power (e.g., two consuls, two praetors, etc.).

[47] The heavy infantry shield (scutum) was a long oval in shape and convex, made of two layers of wood glued together, with canvas and calfskin covers and an iron boss at the centre.

The ore needed to be rich in manganese (an element which remains essential in modern steelmaking processes), but also to contain very little, or preferably zero, phosphorus, whose presence would compromise the steel's hardness.

[54] The Celtic peoples of Noricum (predominantly the Taurisci tribe) empirically discovered that their ore made superior steel around 500 BC and established a major steel-making industry around it.

In response to a desperate appeal by the Norici, the Roman consul Gnaeus Papirius Carbo rushed an army over the Alps and attacked the Germans near Noreia (although, in the event, he was heavily defeated).

When they saw the horrendous injuries inflicted with the Spanish sword – arms hacked off at the shoulder, heads entirely severed, bellies ripped open and guts hanging out – they realised the kind of weapons and the sort of enemy that they were up against, and a wave of fear spread through their ranks.

The socii were summoned to arms by a message from the consuls, ordering each ally to deliver a specified number of troops to a specified assembly place (one location for each consular army) by a set deadline.

Livy relates how, after Cannae, gold rings (a badge signifying equestrian rank), recovered from the corpses of Roman equites formed a pile one modius (about 9 litres) large.

[66] This would have required the depleted ranks of equites to provide at least 252 senior officers (126 tribuni militum, 63 decuriones and 63 praefecti sociorum), plus the army commanders (consuls, praetors, quaestors, proconsuls, etc.).

[69] Against this, Sidnell argues that this view is misguided and that the record shows that Roman cavalry were a formidable force which won a high reputation for skill and valour in numerous battles of the 3rd century BC.

On the left wing, the Romans twice drove back the more numerous and highly rated Gallic cavalry with spirited frontal charges, but pursued too far and became entangled in a melee with the enemy infantry.

[76] A key reason for some historians' disparagement of the Roman cavalry were the crushing defeats at the Trebia and at Cannae, that it suffered at the hands of the Carthaginian general Hannibal during the latter's invasion of Italy (218–216 BC).

This enabled the Romans to field at least an equal number of Numidians at the battle of Zama (202 BC), who, outnumbering the Roman/Italian cavalry by two to one, played a vital role in neutralising their compatriots fighting for Hannibal.

[88] It is during this period of the Republic that a central feature of Roman military practice emerged, which was adhered to until at least c. AD 400 if not beyond: the fortified marching camp (castra), whose earliest detailed description is in Polybius.

[92] Although this practice spared troops the toil of constructing fortifications, it would frequently result in camps often being situated on unsuitable ground (i.e., uneven, waterlogged or rocky) and vulnerable to surprise attack, if the enemy succeeded in scouting its location.

preferably level, dry, clear of trees and rocks, and close to sources of drinkable water, forageable crops and good grazing for horses and pack animals.

[90] After their disaster on the battlefield of Cannae (216 BC), some 17,000 Roman troops (out of a total deployment of over 80,000) escaped death or capture by fleeing to the two marching-camps that the army had established nearby, according to Livy.

A detail of officers (a military tribune and several centurions), known as the mensores ('measurers'), would be charged with surveying the area and determining the best location for the praetorium (the consul's tent), planting a standard on the spot.

The socii appear to have played their role in the new paradigm uncomplainingly, despite the fact that the confederation, previously an alliance primarily designed for mutual defence, was now engaged mostly in aggressive expansion overseas.

It appears from the fragmentary evidence that the conservative majority in the Roman Senate succeeded, by both fair means and foul (such as assassinating reform leaders), in blocking any significant expansion of citizenship among the socii in the period following the agrarian law of 133 BC.