Chapter 9


The Roman army

The Battle of Mons Graupius AD 84. (Illustration by Jennifer Campbell from Antony Kamm, Scotland in Roman Times, Scottish Children's Press 1998)

‘The Britons farther up the hill, who had until then taken no part in the action and had had time contemptuously to observe how small our numbers were, now began gradually to move down the hill in an attempt to outflank the advance, wheel round, and attack from behind. Agricola, who had anticipated this manoeuvre, called up the four cavalry squadrons that he had kept back in case of emergency. So furiously did they charge against the oncoming opposition, that what was intended as a push forward disintegrated into a rout. The tactics of the Britons now rebounded on them, as at Agricola’s command the cavalry squadrons in the thick of the battle disengaged, rode round the packed enemy lines, and took the Britons in the rear.’

(Tacitus, Agricola 37)

The Roman talent for organization is nowhere better illustrated than by its army, the backbone of which was that epitome of the professional fighting man, the legionary. After the civil war, Augustus created a standing army of twenty-eight legions, at which strength, give or take the odd legion, it remained for the next 200 years.

(Illustration by John Pittaway from Picture Reference Ancient Romans, Brockhampton Press 1970)

The legion

Model of legionary headquarters. (VRoma: Chester Museum: Barbara McManus)

Under the republic, new legions were assigned a serial number, with numbers I to IV reserved for those raised by consuls. Whatever the system, and it is not fully understood, at any one time several legions might have the same number. Therefore, to avoid confusion, each also adopted a title or nickname, reflecting the circumstances of its formation, the name of its founder, the place where it was raised, or the front where it had served with most distinction.

A legion’s own standard, often referred to as its ‘eagle’, was carried wherever it went. The eagle was the rallying point for troops in battle and a signal as to where the action was; to lose it to the enemy was both a disaster and a disgrace.

Bronze coin of Caligula commemorating his father Germanicus holding a staff topped with the eagle. The inscription refers to his having recovered the standard from the Germans. (© CNG Coins)

The aquilifer, who carried the legion’s standard, ranked in seniority only just below a centurion. He was also responsible for the safe-keeping of the legion’s pay chest. The imaginifer carried an image of the emperor. Standard-bearers wore animal skins with the heads drawn up over their helmets.

A legion was a self-contained unit which even on the march could rely on its own resources for weeks on end. The legionaries themselves did all the manual work of digging, construction and engineering. Every man carried trenching tools and a pair of stakes which at each stop became components of the camp palisade. He also had to shoulder, or carry on his person, clothes, a cooking-pot, rations and any personal possessions, as well as his weapons and armour.

Surveyor on the march using a groma; having planted it in the ground and checked from the plumb lines that it was upright, he would take a sight along the arms or strings to make a straight line or right angle. (Illustration by Jennifer Campbell from Antony Kamm, Scotland in Roman Times, Scottish Children's Press 1998)

Each legion had a complement of specialists and craftsmen: surveyors, medical and veterinary orderlies, armourers, carpenters, hunters, even soothsayers. The surveyors went ahead of the column of march to select and lay out the site of the night’s camp. The latter was always constructed to the same pattern and surrounded by a ditch, a rampart and a palisade, all of which had to be built afresh each time. Leather tents, each of which slept eight men, were carried by mules.

Battle scene from Trajan's column (cast), with (bottom right) medical orderlies tending the wounded. (VRoma: EUR (Rome), Museum of Roman Civilization: Barbara McManus)

In the field, a legion comprised ten cohorts, each divided into six centuries of eighty men, under the command of a centurion. The commander of a legion (legatus) held his post usually for three to four years; he was assisted by six younger officers, the military tribunes, who were also political appointees. The senior professional officer in the legion was likely to be the praefectus castrorum. He was usually a man of some thirty years’ service, and was responsible for organization, training and equipment. Day-to-day responsibility was therefore in the hands of the centurions, the most senior of whom (centurio primi pili or primus pilus) commanded the first century of the first cohort.

(Left) centurion; (centre) aquilifer; (right) signifer, who carried the century's standard and looked after its savings bank. (Left and right, illustrations by Jennifer Campbell from Antony Kamm, Scotland in Roman Times, Scottish Children's Press 1988; centre, illustration by John Pittaway from Picture Reference Ancient Romans, Brockhampton Press 1970)

Other units

The legions were supported by auxiliary forces, composed of inhabitants of the empire who were not citizens of Rome. All cavalry were auxiliaries. While some auxiliaries fought as infantry and were equipped like legionaries, others retained their native dress and weapons, serving as archers, slingers, spearmen or broadswordsmen. Originally auxiliaries were led by their own chiefs, but in imperial times they were brought within an overall chain of command, under Roman officers.

Under the empire, the only armed forces in Italy were the imperial guard and the cohortes urbanae (city cohorts), who garrisoned Rome itself in order to prevent internal unrest rather than ward off attack from outside. The imperial guard was a crack unit whose members wore special uniforms and received double pay. When the emperor went on campaign, the guard went with him. A further force, the vigiles, recruited from freedmen, patrolled the city of Rome and served as its fire brigade.

A relief in the Louvre, Paris, from the period of Trajan and Hadrian, showing members of the imperial guard, indicated by their rich uniforms and helmets, and oval shields. Behind is a legionary standard, with the eagle holding a thunderbolt in its claws. (Deutches Archaeologisches Institut, Rome)

Up to the time of Augustus, mastery of the seas had been achieved by ad hoc methods and largely foreign naval skills and crews; no Roman citizen ever handled an oar. Augustus established a standing fleet of ships which were his own property and which he manned with freeborn provincials and his own freedmen. His successors saw the wisdom of this initiative, and ten regional flotillas were established under the emperor's overall command. The British flotilla, based at Boulogne, was used by Agricola in AD 83 to soften up the opposition in Scotland with lightning raids up the east coast. According to Tacitus, it also discovered the Orkney Islands and established conclusively that Britain itself was an island.

Coin of Hadrian showing Roman naval vessel with oars and rowers. (VRoma: British Museum: Barbara McManus)

Weapons and tactics

The deployment of the Roman infantry in battle depended on its mobility. Apart from his hob-nailed heavy sandals, a legionary's legs were bare except in colder climates, where tight-fitting knee-breeches were the order of the day. The most usual form of helmet was bronze, with a skull-cap inside and projections to protect the back of the neck and the ears and cheeks. On his left arm a legionary carried a cylindrical leather shield that was also useful as a siege weapon: a body of men crouched underneath their locked-together shields could approach a wall undeterred by missiles hurled from above.

From Trajan's column (cast), men attack a wall under their shields; the formation was known as the "tortoise". (VRoma: EUR (Rome), Museum of Roman Civilization: Barbara McManus)

On the march each man carried a pair of two-metre, metal-headed javelins of different weights. One of these went into battle with him: he threw it at the enemy when in range, before getting down to the serious business of hand-to-hand fighting with his short, double-edged, thrusting and stabbing sword.

A selection of artillery and siege weapons. The largest and most effective was known as the onager (wild ass) because of its kick. Each century was allocated a mechanical arrow-shooter which was deployed in battle. (Illustrations by John Pittaway from Picture Reference Ancient Romans, Brockhampton Press 1970)

A Roman general's objective was to break up and, if possible, break through the enemy lines. Cavalry were mainly employed to head off attacks by the opposition's cavalry and to pursue stragglers. Julius Caesar's favoured tactic was to draw up his cohorts in three lines, each some eight men deep. His first victory in Gaul, at Bibracte in 58 BC, was achieved without cavalry, using a manoeuvre that demanded highly trained and well-disciplined troops.

The battle of Bibracte 58 BC. (From Antony Kamm, The Romans: an introduction, Routledge 1995)

Caesar drew up his four legions in three lines (R). The Helvetii, in close-packed columns, advanced and attacked (H), but were thrown into confusion by the Roman javelins. Then Caesar advanced. The Helvetii retired to a hill to the north (H2). Caesar wheeled to face them, but was attacked in the rear by a force of Boii and Tulingi who had arrived on the scene (B, T). The first two Roman lines continued to face the Helvetii (R2), who returned to the attack (H3). The third Roman line turned about (R3). Both enemy forces were defeated and the Helvetii fled.

Consolidating and patrolling the empire

In republican times, the empire had been allowed to expand as opportunity, circumstances and the Senate decreed. Augustus recognized the need for a specific foreign policy and saw that to undertake random wars of aggression in pursuit of new conquests was uneconomic. Instead, he decided to consolidate provinces and their defences, while always ensuring that no commander could build an overwhelming personal following among his troops. The frontiers of the empire developed according to the lines to which he had withdrawn following the disaster of AD 9, when Publius Quintilius Varus had lost three complete legions, three cavalry regiments and six auxiliary cohorts after being enticed into unfamiliar territory between the rivers Weser and Ems.

The extent of the Roman empire during the rule of Hadrian, including places and peoples outside Italy mentioned on this site. Copyright © Taylor & Francis Group

Tiberius was advised by Augustus not to try to extend the boundaries of the empire, and his immediate successors were either too suspicious or too frightened of the army to pursue a more adventurous policy, with the exception of Claudius and his invasion of Britain in AD 43. (Claudius also altered the status of Mauretania and Thrace from client kingdoms to provinces.)

Scene from Trajan's column: the river god Danubius watches legionaries crossing a pontoon bridge. (VRoma: AICT)

In AD 101 Trajan crossed the river Danube and entered Dacia, violating the treaty agreed between his predecessor Domitian and the king of Dacia. This resulted in a great victory but dubious long-term advantage, and Roman troops finally abandoned the territory in AD 275.

Some legions remained on the same station for many years; others were deployed as needed. The Second Augusta and the Twentieth Valeria Victrix spearheaded the invasion of Britain in AD 43 and were among the last to be evacuated in AD 400. The Twentieth was also Agricola’s strike force in northern Britain, and helped to build both Hadrian’s and the Antonine walls.

Plaster cast of distance-slab from the Antonine Wall. (VRoma: Hunterian Museum, Glasgow: Susan Bonvallet)

Originally, the extent of occupation of a region was bounded by a limes (plural limites), which meant simply a path or track. Then it came to refer to a military road that linked the permanent forts housing units of a legion, whose task it was to discourage hostile military gatherings beyond the line, keep the peace and encourage Romanization within it, and allow free movement for trade across it. Thus, limes came to mean boundary or frontier and the English word from it to signify something that ‘may not be passed’. Sometimes, as in the cases of Hadrian’s and the Antonine walls in Britain, a limes was an actual wall.

Hadrian also reviewed the physical boundaries of the whole empire, and strengthened with a wooden palisade the defences of the Rhine.

Reconstructed fortification marking the boundary of the Roman empire in Germany, showing palisade and ditch. (VRoma: Saalburg Museum: Barbara McManus)

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