The Phalanx Legion (753-300 BC)            

Ab Urbe Condita (by Livy 59 BC-AD 17) covers the history of Rome, from its founding by Romulus until 9 BC. The city was protected by the populus (a Latin word which originally meant army).

The organization and command structure of the king’s army, a combined force of 3,300 infantry and cavalry, is unknown. The three (Etruscan-named) Roman tribes (the root of the Latin word for tribes, tribus, meant thirds), the Luceres, Ramnes and Tities, each contributed 10 centuries of infantry (1,000 men) and 100 cavalry (10 decuries). Levies were self-equipped, and the wealthiest citizens formed the cavalry (equites). According to Varro (116-27 BC) the word for the common soldier, miles, derives from the 1,000 man (milles) tribal contingent.

Greek hoplite formations became popular around 675 BC, and by 600 BC the Etruscans had adopted hoplite equipment (round shields and spears) and tactics (a tight phalanx formation).

Roman army transition to the hoplite phalanx was facilitated by King Servius Tullius (578-535 BC), whose Etruscan name was Mastarna, when he created the comitia centuriata and organized Rome’s citizenry into five propertied classes. Unlike the Etruscan model, the basis for recruitment into the Roman army revolved around citizenship and voting rights.

Historians Titus Livius (59 BC – 12 A.D.) and Dionysius of Halicarnassus (who died 8 BC) tell us that each class participated according to its means, and individual soldiers financed their own equipment. The seniores (men 46 and over) comprised half of each class, and they defended Rome while the juniores (age 17-45) took to the field. Livy breaks down the classes in Ab Urbe Condita as follows (Dionysius’ description differs in some respects):

  • The 1st class (assessed at over 100,000 asses) consisted of 80 centuries of heavy infantry. Added to this class were 2 centuries of engineers. The infantry was equipped in the same manner as Greek hoplites with swords and spears and bronze shields (the round clipeus), breastplates, helmets, and greaves.
  • The 20 centuries of the 2nd class (assessed at 75,000 to 100,000 asses) were equipped as the 1st Class but with rectangular shields and no breastplates.
  • The 20 centuries of the 3rd class (assessed at 50,000 asses) were outfitted similar to the 2nd but without greaves.
  • The 20 centuries of the 4th class (assessed at over 25,000 asses) consisted of men armed only with spears and shields.
  • The 5th class (assessed at 11,000 asses) was composed of 30 centuries of slingers plus 2 centuries of trumpeters and mechanics.
  • The capite censi (citizens, with minimal to no property) were excluded from service and organized into a single century. They supplied the necessary labour to build and maintain equipment.

Livy says that ServiusHaving thus divided and armed the infantry … levied twelve centuries of knights from among the chief men of the state.”

Because the soldiers were levied from the classes the name for the army changed; populus changed to legion (legio, legionis) based on the Latin verb legere (to choose or levy).

The 40 1st Class centuries of juniores formed a phalanx of 4,000 to 4,200 infantry (principes, hastati, and triarii) plus 600 cavalry.

Following the abolition of the monarchy in 509 BC armies were raised by magistrates (two praetors) for a March-October campaign season; the legion was typically disbanded in the autumn and reformed over the winter. During extended sieges (i.e., against the Veii) or periods when it was necessary to permanently garrison a conquered region only soldiers eligible for retirement were discharged.

The total number of centuries in the legion grew to 60, perhaps as late as 400 BC, when the 2nd and 3rd classes each contributed 10 centuries (1,000 men) of juniores.

The Manipular Legion (4th-3rd Century BC)

The defeat of the Roman army at Allia by the Gauls, and the subsequent 390 B.C sack of Rome exposed the tactical limitations of the phalanx. Marcus Furius Camillus (446-365 BC), known as the 2nd founder of Rome, liberated the city from the Gauls. Livy and Plutarch credit him with introducing the oval scutum (shield) and pilum (javelin) as well as compensating troops with pay. Although he is acknowledged by some sources as being responsible for the transition to the manipular army, it is more likely the result of gradual evolution between 390 and 340 BC.

The annual levy grew from one to two legions by 362 BC at which time the word legion no longer described the army as a whole but referenced a unit within the army. Livy says that there were 4 legions by 340 BC (others suggest that was closer to 311 BC).

The First Samnite War 343 to 341 BC demonstrated the weakness of the phalanx in mountainous terrain.

Rome’s response was the adoption of the flexible maniple system (described as a “phalanx with joints”). The centuries were paired (one prior and one posterior) in maniples (from the word manipulus/manipuli meaning handfuls).

In battle formation each legion was organized into three lines (triplex acies) of heavy infantry arrayed in a checkerboard (quincunx) fashion. The gaps between the maniples in each line were covered by the line immediately to the rear. Each maniple had a front of 60’ with equivalent size gaps between each maniple to permit the interchange of lines and allow for the harmless/controlled passage of enemy chariots or elephants during combat. The front of the legion (allowing for overlap) was 360 metres (1,200 feet) and the spacing between the lines was 75 metres (250 feet).

For administrative purposes one maniple from each of the three lines formed a cohort. Every Roman with a net worth of 11,000 asses between the ages of 17-45 was compelled to serve and was subject to conscription (dilectus).

We turn to a man who lived when the manipular legion was active for a more detailed look at its structure. Polybius, the educated son of a wealthy Greek (Achaean) statesman, described the events from 264-146 BC in The Histories.  He was a cavalry commander who was captured at Pydna in 168 BC and sent to Rome as a detainee. There he became the mentor and friend of Scipio Africanus Aemilianus (185-129 BC) and was present at the fall of Carthage in 146 BC.

Polybius tells us that by the 2nd Punic War (221-202 BC) the army consisted of 4 legions under two consuls. The three lines were reorganized based on age versus property.

  • The 1st line consisted of (the hastate) the youngest and least experienced men (1,200 men at 60 per century in 10 maniples).
  • The 2nd line was comprised of principes (leaders) experienced soldiers and family men in their late twenties and early thirties (1,200 men at 60 per century in 10 maniples).
  • The 3rd line was home to the (triarii) veterans (600 men in 10 maniples) who formed an emergency reserve.

Each soldier was equipped with a 4’ by 2′ oval shield (scutum) weighing 22 pounds and a short Spanish thrusting sword (the gladius Hispaniensis which was modelled after the sword favoured by Carthage’s Iberian mercenaries). Armour (Montefortino, Attic or Corinthian helmets, greaves and breast plates) varied as the cost was funded by each individual soldier. The hastati and principes carried two javelins (pila), possibly of Etruscan or Samnite origin, whereas the triarii used the thrusting spear (hasta).

The rorarii and accensi may have transitioned into the 1,200 velites (cloak-wearers); they were inexperienced young men who preceded the other lines as a screen. Each veles was equipped with a light 4-foot javelin, a sword, and a hide-covered 3-foot wicker shield. They were not organized into formal units and could advance and retreat through the heavy infantry as required. The 300 legionary cavalrymen were equipped with body armour, a circular shield, a sword and a lance.

The Cohortal Legion (2nd Century BC)

When Gaius Marius became consul in 108 BC he was almost immediately appointed to succeed Quintus Caecilius Metellus as the commander of the campaign against Jugurtha in Africa.

Marius, faced with a shortage of recruits, opened up enlistment to all citizens (non-propertied men of free birth irrespective of social rank), and the legions swelled with volunteers (aged 17 and older). Recruits escaped poverty, learned a trade, enjoyed superior medical attention, were well fed, had the opportunity to travel the empire, and received a bonus (typically of farmland) upon retirement.

Marius’ open-door recruitment policy was welcomed by the draft-eligible property owners as it freed them from service and increased the time they could devote to wealth accumulation.

Around 101 BC Marius, lauded as the 3rd founder of Rome, abolished the velites and replaced the maniple (which was too small, had too many gaps, and was vulnerable to collapse under aggressive enemy attack) with the cohort as the basic tactical unit.

Military kit was standardized. Greaves were dropped (except in the case of centurions) and soldiers were equipped with a helmet, shield (scutum), armour (typically Celtic chain mail known as the lorica hamata), sword (gladius), dagger (pugio), hob-nailed sandals (caligae), entrenching tools and two javelins (pila). Each of Marius’ mules, as the soldiers were nicknamed, shouldered 66 pounds (35 kgs) of equipment (inclusive of three days of rations).

Marius reintroduced the use of the shield as a weapon to push and corral the enemy. The pilum, universally carried by all ranks, was designed to bend (the iron shank was not hardened) or break apart upon impact. Marius stressed fitness and martial training to endow his men with self-confidence. He conferred a silver eagle (associated with the god Jupiter) upon each legion as its new primary standard.

In battle the normal triplex acies (quincunx) formation consisted of 4 cohorts in the first line, 3 in the second and 3 in the third. At 60 to 80 men per century (which was typical) legion strength fluctuated between 3,600 and 4,800 men (6,000 if the centuries were fully populated) including 120 cavalrymen. Marius is likely responsible for reducing the number of 1st cohort centuries from six to five; they were subsequently doubled in size by the mid-1st century AD.

By the end of the Social War in 87 BC, nearly the entire free population of Italy south of the Po was eligible to enlist. The alae sociorum (units previously provided by allied cities) vanished, military salaries were state funded and elected magistrates no longer commanded the legions.

Julius Caesar initiated recruitment of Latins north of the Po as well as native Gauls. The conflict between Pompeii and Caesar, the war with Brutus, and the clash between Antony and Augustus completed the transformation of the army from a militia into the world’s first professional army.