The Roman legion, the largest military unit of the Roman army, was composed of Roman citizens serving as legionaries. During the Roman Republic the manipular legion comprised 4,200 infantry and 300 cavalry. After the Marian reforms in 107 BC the legions were formed of 5200 men and were restructured around 10 cohorts, the first cohort being double strength. This structure persisted throughout the Principate and Middle Empire, before further changes in the fourth century resulted in new formations of around 1000 men.
The Praetorian Guard was an elite unit of the Imperial Roman army that served as personal bodyguards and intelligence agents for the Roman emperors.
A cohort was a standard tactical military unit of a Roman legion. Although the standard size changed with time and situation, it was generally composed of 480 soldiers. A cohort is considered to be the equivalent of a modern military battalion. The cohort replaced the maniple. From the late second century BC and until the middle of the third century AD, ten cohorts made up a legion. Cohorts were named "first cohort", "second cohort", etc. The first cohort consisted of experienced legionaries, while the legionaries in the tenth cohort were less experienced.
A legatus was a high-ranking Roman military officer in the Roman army, equivalent to a high-ranking general officer of modern times. Initially used to delegate power, the term became formalised under Augustus as the officer in command of a legion.
The equites constituted the second of the property-based classes of ancient Rome, ranking below the senatorial class. A member of the equestrian order was known as an eques.
Lucius Artorius Castus was a Roman military commander. A member of the gens Artoria, he has been suggested as a potential historical basis for King Arthur.
Vigiles or more properly the Vigiles Urbani or Cohortes Vigilum were the firefighters and police of ancient Rome.
In the Roman army during classical antiquity, a centurion, was a commander, nominally of a century, a military unit originally consisting of 100 legionaries. The size of the century changed over time, and from the first century BC through most of the imperial era was reduced to 80 men.
Poenius Postumus was praefectus castrorum of the Roman legion II Augusta, stationed in Britain during the rebellion of Boudica in 61 AD. In this position he would have been in charge of all administrative, training and equipment matters, and would also have been acting commander of the legion in the absence of its two most senior officers: the legate (legatus) and the senior military tribune.
A military tribune was an officer of the Roman army who ranked below the legate and above the centurion. Young men of Equestrian rank often served as military tribune as a stepping stone to the Senate. The tribunus militum should not be confused with the elected political office of tribune of the people (tribunus plebis) nor with that of tribunus militum consulari potestate.
Centuria is a Latin term denoting military units originally consisting of 100 men. The size of the centuria changed over time, and from the first century BC through most of the imperial era the standard size of a centuria was 80 men. By the time of Roman Empire, ordo became a synonym of centuria.
Praefectus, often with a further qualification, was the formal title of many, fairly low to high-ranking, military or civil officials in the Roman Empire, whose authority was not embodied in their person but conferred by delegation from a higher authority. They did have some authority in their prefecture, such as controlling prisons and in civil administration.
The auxilia were introduced as non-citizen troops attached to the citizen legions by Augustus after his reorganisation of the Imperial Roman army from 27 BC. By the 2nd century, the Auxilia contained the same number of infantry as the legions and, in addition, provided almost all of the Roman army's cavalry and more specialised troops. The auxilia thus represented three-fifths of Rome's regular land forces at that time. Like their legionary counterparts, auxiliary recruits were mostly volunteers, not conscripts.
The praefectus castrorum was, in the Roman army of the early Empire, the third most senior staff officer of the Roman legion after the legate (legatus) and the senior military tribune, both of whom were from the senatorial class. The praefectus castrorum was a quartermaster responsible for military logistics and requisition but could command the legion whenever the senior commanders were absent. The post was usually held by a soldier promoted from the centurionate, having already served as a chief centurion of a legion, and was therefore open to ordinary, plebeian citizens. Prefects of this rank, for example Sextus Vibius Gallus, were awarded prizes (dona) to mark their achievements.
In the Roman army of the late Republic and the Principate, the tribunus laticlavius was one of the six military tribunes in a legion. Usually, it consisted of young men around age 20 who belonged to a wealthy family or were friends with the legate. The position of tribunus laticlavius was the first step on the Cursus honorum. Tribunus laticlavius are typically depicted wearing a purple cloak.
Publius Aelius Aelianus was a senior officer in the Imperial Roman army in the mid-3rd century AD who rose from lowly origins to become the prefect of a legion under Emperor Gallienus. He was one of the earliest beneficiaries of Gallienus's policy that effectively excluded senators from army commands in favour of career-soldiers of equestrian rank. His later life is obscure.
A tribunus angusticlavius was a senior military officer in the Roman legions during the late Roman Republic and the Principate.
The Imperial Roman army was the military land force of the Roman Empire from 27 BC to 476 AD, and the final incarnation in the long history of the Roman army. This period is sometimes split into the Principate and the Dominate (284–476) periods.
Traianus Mucianus was a Roman soldier of Thracian origins of the second half of the Third Century AD who rose from the lowest ranks of the army to senior commands. He was almost certainly a remarkable soldier. However, the successive promotions he secured in the latter part of his career are thought to owe much also to the favour shown him by men highly placed in the Imperial entourage whose patronage secured him advantageous postings in the Imperial comitatus, the mobile field force under the direct command of the Emperor, that was undergoing massive expansion at this time.
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