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The Roman Army: a Glossary
The units, ranks, equipment and honours of the Roman army, from the manipular legion of the Republic to the field armies of the late empire.
Quiz yourself on these in RomeDrill →| Term | Meaning |
|---|---|
| Legion | The basic large unit of the Roman army (Latin legio, 'levy'). The mid-Republican legion described by Polybius had 4,200 infantry and 300 cavalry; the imperial legion had about 5,000-5,500 men in ten cohorts and was recruited from Roman citizens. |
| Praetorian Guard | The emperor's bodyguard (cohortes praetoriae), formally organised by Augustus in 27 BC in nine cohorts. Sejanus concentrated them in the Castra Praetoria in AD 23. They murdered and made emperors (Caligula, Claudius, Pertinax, the auction of 193) until Constantine disbanded them after the Milvian Bridge (312). |
| Ballista | Roman torsion engine derived from Greek models, with two arms set in vertical spring-frames. In the early Empire the term means chiefly the stone-thrower; later it was used for bolt-shooters. Vegetius credits each legion with 55 cart-mounted carroballistae. |
| Castra | Roman military camp or fortress (singular castrum is rare in this sense). Marching camps and permanent bases shared a plan: ditch and rampart, rounded corners, the via principalis and via praetoria meeting at the headquarters (principia). The word survives in English place names in -chester, -caster and -cester. |
| Centurion | Professional officer commanding a century; the backbone of the legion. He wore a transverse crest and carried the vitis (vine staff) as badge of rank and instrument of punishment. A legion had 59, ranked by cohort and century up to the primus pilus. |
| Cohort | Standard tactical sub-unit of the legion from the late Republic: six centuries of 80 men, about 480 in all. From the Flavian period the first cohort was double strength, with five double centuries (about 800 men). Auxiliary infantry units were also called cohorts. |
| Decimation | Decimatio: the execution by lot of every tenth man of a unit guilty of cowardice or mutiny, carried out by the other nine with cudgels (fustuarium); survivors were put on barley rations. Always rare, it was revived by Crassus against troops who fled from Spartacus. |
| Foederati | Allies bound by a treaty (foedus). In the late Empire the term means barbarian groups serving as units under their own leaders; Theodosius I's settlement of the Goths inside the Empire in 382 set the pattern that led to Visigothic, Burgundian and Frankish kingdoms on Roman soil. |
| Gladius | Short sword of the legionary (blade about 50-60 cm), used chiefly for thrusting from behind the shield. The 'gladius Hispaniensis' was adopted from Spanish models around the Second Punic War; later variants are named the Mainz and Pompeii types. Gave its name to the gladiator. |
| Legiones XVII, XVIII, XIX | The army of Publius Quinctilius Varus, destroyed by Arminius in AD 9. Two of the three lost eagles were recovered during Germanicus' campaigns (AD 15-16) and the third under Claudius in AD 41. Suetonius has Augustus crying 'Quinctilius Varus, give me back my legions!' |
| Limes | A fortified imperial frontier (plural limites). The best known are the Upper German-Raetian limes (about 550 km of palisade, ditch, wall and some 900 towers), the limes Arabicus, the fossatum Africae, and the walls of Hadrian and Antoninus in Britain. |
| Trireme | Galley with three levels of oarsmen (about 170 rowers in the Athenian version) and a bronze ram. Superseded as ship of the line by larger polyremes in the Hellenistic period, it was the commonest larger type in the imperial fleets at Misenum and Ravenna. |
| Triumph | Ceremonial victory procession granted by the Senate to a commander holding imperium. It passed from the Campus Martius through the Porta Triumphalis, the Circus Maximus and along the Via Sacra to the Capitol. Tradition required 5,000 enemy dead. After Cornelius Balbus in 19 BC it was reserved for the imperial family. |
| Ala | Auxiliary cavalry regiment, the best-paid arm of the auxilia. An ala quingenaria had 16 turmae (about 500 men), an ala milliaria 24 (about 1,000). In the Republic the word meant the 'wings' of Italian allies flanking the legions. |
| Aquila | Legionary eagle. According to Pliny, Marius in 104 BC made it the sole standard of the legion, abolishing the wolf, minotaur, horse and boar. Lost eagles - those of Crassus at Carrhae (returned by Parthia in 20 BC) and of Varus - were recovered with great fanfare. |
| Aquilifer | Bearer of the legionary eagle (aquila); one per legion, attached to the first cohort. At Caesar's first landing in Britain (55 BC) the aquilifer of the Tenth leapt into the surf to shame his comrades into following. |
| Auxilia | The 'helpers': regular units recruited from provincials without citizenship (peregrini), organised by Augustus into infantry cohorts, cavalry alae and mixed cohortes equitatae. Honourable discharge after 25 years brought citizenship, recorded on a bronze diploma. |
| Bucellarii | Private bodyguard troops of late Roman commanders and great landowners, named after the bucellatum (army hardtack). Stilicho, Aetius and later Belisarius all had large bands; the murder of Valentinian III in 455 was carried out by former bucellarii of Aetius. |
| Caligae | Military sandal-boots with thick soles studded with iron hobnails, standard to about the end of the 1st century AD. Germanicus' small son Gaius, dressed as a soldier in the Rhine camps, was nicknamed Caligula, 'little boot'. |
| Century | The legion's basic company (centuria), commanded by a centurion. Despite the name it numbered 80 men under the Principate: ten contubernia of eight. An imperial legion had 59 centuries. |
| Classis Misenensis | The praetorian fleet at Misenum, established by Augustus as the premier naval force, guarding the western Mediterranean. Pliny the Elder died commanding it during the eruption of Vesuvius; a detachment at Rome rigged the Colosseum's velarium. |
| Classis Ravennas | The praetorian fleet of Ravenna, covering the Adriatic and eastern Mediterranean. Its harbour suburb, Classis, survives in the name Classe. Provincial fleets included the classis Britannica, Germanica, Pannonica, Moesica, Pontica, Syriaca and Alexandrina. |
| Comitatenses | Troops of the late Roman field armies (from comitatus, the emperor's retinue), developed under Diocletian and given definitive form by Constantine. They ranked above the frontier troops; the elite among them were the palatini. |
| Contubernium | The smallest unit of the Roman army: eight soldiers (contubernales) sharing a tent on campaign and a pair of rooms in barracks. Ten contubernia formed a century of 80. |
| Corona civica | The 'civic crown' of oak leaves, second in prestige among military decorations, given for saving a citizen's life in battle and holding the ground. The man saved had to attest the deed. Julius Caesar won one at Mytilene (c. 80 BC); on Augustus' coins it carries the legend OB CIVIS SERVATOS. |
| Corona muralis | The 'mural crown': a gold circlet shaped like turreted walls, given to the first man to scale the wall of a besieged city. In art it is also the headdress of city goddesses such as Tyche and Cybele. |
| Corona navalis | The naval crown (also corona rostrata or classica), originally for the first man to board an enemy ship. It was awarded very rarely; the most famous recipient was Agrippa after Naulochus (36 BC). |
| Corona obsidionalis | The 'siege crown' or 'grass crown' (corona graminea), conferred by the soldiers themselves on a general who saved a besieged or trapped army. Pliny the Elder lists only a handful of recipients, among them Fabius Maximus, Scipio Aemilianus and Sulla. |
| Corona vallaris | Also called corona castrensis: gold crown bearing a representation of rampart stakes, for the first man across the rampart of an enemy camp. |
| Corvus | Boarding device described by Polybius - a gangway about 11 m long mounted on a pole at the prow, with an iron beak to pin the enemy ship. It won Gaius Duilius the battle of Mylae (260 BC) and was used at Ecnomus (256 BC), but its top-weight may have contributed to catastrophic storm losses, and it was abandoned. |
| Equites singulares Augusti | Imperial horse guard, probably established by Trajan, recruited from the best troopers of the auxiliary alae (many of them Germans and Pannonians). Having fought for Maxentius, they were dissolved by Constantine in 312, who built the Lateran basilica over their barracks. |
| Frumentarii | Soldiers seconded from the legions, originally for grain supply (frumentum), who by the 2nd century served as imperial couriers, informers and assassins, headquartered in the Castra Peregrina at Rome. Hated for their abuses, they were abolished by Diocletian and replaced by the agentes in rebus. |
| Hastati | Front-line heavy infantry of the mid-Republican legion: men in their early twenties armed with scutum, gladius and two pila (despite a name derived from the hasta, or spear). There were 1,200 per legion in ten maniples. |
| Legatus legionis | Commander of a legion under the Principate, a senator (normally of praetorian rank) chosen by the emperor. In a one-legion province he was also the governor. The legions of Egypt, closed to senators, were commanded by equestrian prefects instead. |
| Legio II Augusta | Under Vespasian in AD 43-47 it fought through southern Britain, taking the Isle of Wight and some twenty hillforts. From about AD 75 its fortress was Caerleon. Its camp prefect Poenius Postumus disgraced it by ignoring the summons to fight Boudica. |
| Legio II Parthica | One of three 'Parthian' legions created by Severus c. 197. Its base at Castra Albana (Albano Laziale), a day's march from Rome, gave the emperor a strategic reserve and a counterweight to the Senate and the Guard. |
| Legio III Augusta | The garrison of Africa-Numidia, stationed at Ammaedara, then Theveste, then Lambaesis (where Hadrian's address to it survives on stone). Dissolved by Gordian III in 238 and its name erased from inscriptions, it was reconstituted under Valerian in 253. |
| Legio IX Hispana | One of the four legions of the Claudian invasion of Britain, based at Lincoln and then York (Eboracum). Its disappearance - it is missing from a legion list of the 160s - has been blamed on a disaster in Britain, the Bar Kokhba revolt or the Parthian war of 161; traces at Nijmegen suggest it left Britain first. |
| Legio V Alaudae | Recruited by Caesar about 52 BC at his own expense from Gauls, who were later enfranchised - the first legion raised from provincials. Its name probably refers to a crest resembling the lark's. It disappears in the later 1st century, perhaps destroyed on the Danube under Domitian. |
| Legio VI Victrix | Founded by Octavian; served in Spain and then Lower Germany before transferring to Britain c. 122, where it replaced the Ninth at York and built parts of Hadrian's Wall. It was still at York in the Notitia Dignitatum. |
| Legio X Equestris | Caesar's Tenth, the legion he trusted most in Gaul and the Civil War (the Sabis, Pharsalus, Munda); he quelled its mutiny in 47 BC by addressing the men as 'Quirites' (civilians). Reconstituted after his death and later merged with other troops, it became X Gemina. |
| Legio X Fretensis | Raised by Octavian and named after the Fretum Siculum, where it fought Sextus Pompey. Under Titus it camped on the Mount of Olives during the siege of Jerusalem; under Flavius Silva it took Masada (AD 73/74). Its emblems included the boar, bull and galley. Later moved to Aila on the Red Sea. |
| Legio XII Fulminata | Routed with Cestius Gallus' army at the start of the Jewish Revolt, it redeemed itself at the siege of Jerusalem and was then posted to Melitene on the Euphrates in Cappadocia, where it stayed for centuries. |
| Legio XIII Gemina | Raised by Caesar in 57 BC, it was the only legion with him when he invaded Italy. Under the Empire it served on the Danube, fought in both Dacian Wars and was the long-term garrison of Apulum (Alba Iulia). Its emblem was the lion. |
| Legio XIV Gemina | Based at Wroxeter in Britain, it won the decisive battle against Boudica (AD 60/61) with detachments of the Twentieth. Withdrawn from Britain for good in 70, it served at Mainz and then for centuries at Carnuntum on the Danube. |
| Legio XX Valeria Victrix | One of the four invasion legions of 43, stationed successively at Colchester, Usk, Wroxeter, Inchtuthil and, from the late 80s, Chester. Its titles were probably won in the defeat of Boudica (AD 60/61). It worked on both Hadrian's Wall and the Antonine Wall. |
| Liburnian | The liburna: a swift bireme derived from the ships of the Liburni of the Dalmatian coast. Agrippa's lighter vessels of this kind outmanoeuvred Antony's heavy ships at Actium (31 BC); by late antiquity the word meant simply 'warship'. |
| Limitanei | Frontier garrison troops of the late Roman army, as distinct from the mobile comitatenses. They policed the borders and held the forts, with lower pay and privileges; the old view of them as mere part-time peasant militia is now thought exaggerated. |
| Lorica hamata | Mail armour, adopted from the Gauls by the 3rd century BC and worn by legionaries and auxiliaries throughout Roman history. Scale armour was called lorica squamata. |
| Lorica segmentata | Articulated plate armour of iron hoops and shoulder plates, in use from the reign of Augustus (fragments were found at Kalkriese, the Varus battlefield of AD 9) to the 3rd century. The name was coined in the 16th century; the Roman term is unknown. |
| Maniple | Tactical unit (manipulus) of the mid-Republican legion, adopted during the Samnite Wars in place of the phalanx. Each legion had 30: ten each of hastati, principes and triarii, deployed in three lines with gaps (the triplex acies). Maniples of hastati and principes had about 120 men, those of triarii 60. |
| Marius' mules | 'Muli Mariani': legionaries who, following Gaius Marius' reforms (c. 107-101 BC), carried their own pack (sarcina) - rations, tools, cooking gear and stakes - slung on a pole (furca), some 30 kg or more in all. |
| Military diploma | Modern name for the bronze certified copy of an imperial constitution granting citizenship and conubium to a veteran of the auxilia, fleets or guard units; the original was posted in Rome. Examples run from the reign of Claudius to the 3rd century and are a key source for unit movements. |
| Missio honesta | Honourable discharge, as opposed to missio causaria (medical) and missio ignominiosa (dishonourable). Under Augustus a legionary veteran received a praemium of 12,000 sesterces, paid from the aerarium militare founded in AD 6; service settled at 25 years. |
| Onager | Single-armed stone-throwing engine with a sling, described by Ammianus Marcellinus in the 4th century. Vegetius assigns ten to each legion, one per cohort. |
| Optio | Deputy of the centurion, one per century, named from optare ('to choose'). He carried a staff (hastile), kept order from the rear of the formation and took command if the centurion fell. Below him ranked the tesserarius, keeper of the watchword. |
| Ovation | Ovatio: a minor triumph awarded when the enemy was judged unworthy (slaves, pirates) or the victory incomplete or bloodless. Crassus received one for defeating Spartacus (71 BC); Aulus Plautius, conqueror of Britain, received one in AD 47. |
| Pilum | The legionary's heavy throwing spear, hurled in a volley at some 15-30 m just before the charge. Its pyramidal point and long soft-iron shank penetrated shields and rendered them useless. Each man typically carried two. |
| Praefectus castrorum | The 'camp prefect': a veteran ex-primus pilus who ranked third in the legion after the legate and the senatorial tribune. He oversaw the fortress, supplies, artillery and building work, and commanded in the absence of his superiors. |
| Praetorium | Originally the general's (praetor's) tent at the centre of the camp; in permanent forts the commander's courtyard house next to the principia. The term also came to mean a governor's official residence, as in the Gospels. |
| Primus pilus | 'First spear' (properly 'first file'): the chief centurion of the legion, commanding the first century of the first cohort and sitting in the legate's council. Held for one year, the post gave entry to the equestrian order and often led to the camp prefecture. |
| Principes | Second-line heavy infantry of the mid-Republican legion: experienced men in their late twenties and thirties, equipped like the hastati with scutum, gladius and pila. 1,200 per legion in ten maniples. |
| Principia | Headquarters of a fort or fortress, at the junction of the via principalis and via praetoria. It contained offices, a basilica-like cross-hall with tribunal, and the aedes or sacellum housing the standards, the emperor's image and the strongroom. |
| Pugio | Leaf-bladed military dagger about 20-28 cm long, a sidearm of legionaries and auxiliaries, often in a richly decorated sheath. The assassins' dagger appears between two on the 'EID MAR' coin of Brutus. |
| Quinquereme | Large oared warship with five rowers to each vertical group of oars. According to Polybius, Rome built its first fleet of 100 in 60 days in 261-260 BC, copying a Carthaginian ship that had run aground. |
| Sacramentum | The soldier's oath (sacramentum militare) to obey his commanders and not desert. Under the Empire it was sworn to the emperor and renewed annually, on 3 January from the Flavian period. The word is the origin of 'sacrament'. |
| Scholae palatinae | The late Roman imperial guard, probably created by Constantine to replace the Praetorians. The Notitia Dignitatum lists five scholae in the West and seven in the East; forty picked men, the candidati, formed the emperor's personal escort. |
| Scorpio | Light torsion catapult shooting bolts, described by Vitruvius. Confusingly, Ammianus reports that in his day the same name was applied to the one-armed stone-thrower. |
| Scutum | Legionary shield of laminated wood covered in leather or canvas, with an iron or bronze boss (umbo) used for punching. Adopted from Italic peoples in place of the round clipeus; the rectangular curved form is characteristic of the 1st-2nd centuries AD and made the testudo possible. |
| Signifer | Bearer of the signum, the standard of a century or maniple (a pole with discs and often an open hand). He also kept the unit's pay and savings accounts. Related posts were the imaginifer (emperor's image) and vexillarius (flag). |
| Spatha | Straight sword with a blade of roughly 75-100 cm, of Celtic origin, carried by auxiliary cavalry in the early Empire and by all troops from the later 2nd-3rd century. Ancestor of the early medieval sword and of the words épée and espada. |
| Speculatores | Originally scouts and spies; under the Principate each legion supplied ten to the provincial governor's staff as messengers, gaolers and executioners, while a mounted corps of praetorian speculatores formed the emperor's close escort in the 1st century AD. |
| Spolia opima | The 'rich spoils', the rarest Roman honour. The three winners were Romulus (over Acron of Caenina), Aulus Cornelius Cossus (over Lars Tolumnius of Veii, c. 437 BC) and Marcus Claudius Marcellus (over the Gaul Viridomarus at Clastidium, 222 BC). Octavian blocked Crassus' grandson from claiming them in 29 BC. |
| Testudo | Shield formation giving all-round protection against missiles, used in sieges and, by Mark Antony's men, against Parthian archers (36 BC). It is depicted on Trajan's Column and the Column of Marcus Aurelius. |
| Triarii | The oldest and most experienced soldiers of the mid-Republican legion, forming the third line and still armed with the thrusting spear (hasta). Only 600 per legion, in ten maniples of 60. 'Res ad triarios venit' ('it has come to the triarii') meant a fight to the last resort. |
| Tribunus militum | Military tribune. Each legion had six: in the Republic they were elected and commanded in rotation; under the Principate one was a senatorial tribunus laticlavius (the nominal second-in-command) and five were equestrian tribuni angusticlavii. |
| Triplex acies | The 'triple battle line' of the manipular legion: hastati in front, principes behind them, triarii in reserve, with maniples staggered in a chequerboard (quincunx). Caesar's cohort legions still normally deployed in three lines. |
| Turma | The basic cavalry sub-unit, about 30 riders under a decurio. The 300 cavalry of a Republican legion formed ten turmae; an auxiliary ala quingenaria had sixteen. |
| Urban cohorts | Cohortes urbanae: paramilitary police of Rome under the praefectus urbi, originally three cohorts numbered X-XII to follow on from the nine praetorian cohorts. Later detachments also guarded the mints at Lugdunum and Carthage. |
| Vallum | Defensive rampart of a camp, built from the spoil of the ditch (fossa) and topped with stakes (valli, pila muralia) carried by the soldiers. Modern scholars also use 'the Vallum' for the flat-bottomed ditch and mounds running south of Hadrian's Wall. |
| Velites | Light-armed skirmishers of the mid-Republican legion, 1,200 per legion, drawn from the youngest and poorest recruits. They carried light javelins (hastae velitares), a sword and a round shield (parma), and disappeared with the reforms of the late 2nd century BC. |
| Vexillatio | Temporary task force detached from its parent unit(s), the normal way of reinforcing a war zone from the 2nd century AD without stripping a frontier. In the late army the word came to mean a cavalry regiment. |
| Vexillum | Flag-type standard, usually red or purple with the unit's name or emblem, carried by a vexillarius. A red vexillum raised over the general's tent was the signal for battle. It is the origin of the term 'vexillology'. |
| Vigiles | Rome's fire brigade and night watch, founded by Augustus in AD 6 under an equestrian praefectus vigilum. Seven cohorts recruited from freedmen covered the fourteen regions, fighting fires with buckets, pumps (siphones), hooks and demolition. |
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