The Roman legion, the largest military unit of the Roman army, comprised 4,200 infantry and 300 equites (cavalry) in the period of the Roman Republic and 5,600 infantry and 200 auxilia in the period of the Roman Empire.
The Praetorian Guard was an elite unit of the Imperial Roman army that served as personal bodyguards and intelligence agents for the Roman emperors.
Legio II Augusta was a legion of the Imperial Roman army that was founded during the late Roman republic. Its emblems were the Capricornus, Pegasus, and Mars. It may have taken the name "Augusta" from a victory or reorganization that occurred during the reign of Augustus.
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.
Legio IX Hispana, also written as Legio VIIII Hispana, was a legion of the Imperial Roman army that existed from the 1st century BC until at least 120 AD. The legion fought in various provinces of the late Roman Republic and early Roman Empire. The nickname "Hispana" was gained when it was stationed in Hispania under Augustus. It was stationed in Britain following the Roman invasion in 43 AD. The legion disappears from surviving Roman records after c. 120 AD and there is no extant account of what happened to it.
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.
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.
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 primus pilus or primipilus was the senior centurion of the first cohort in a Roman legion, a formation of five double-strength centuries of 160 men; he was a career soldier and advisor to the legate. The primus pilus would remain in command for one year. They could continue to serve in the army after their term ended if there was a vacancy in command or if they wished to become an independent commander of an auxilia unit or the praefectus castrorum.
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.
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.
Lucius Petronius Taurus Volusianus was a Roman citizen, apparently of equestrian origins, whose career in the Imperial Service in the mid-Third Century AD carried him from a relatively modest station in life to the highest public offices and senatorial status in a very few years. He may have secured his first appointments before the Licinian Dynasty – – acceded to the Empire in 253 AD, but it was in the course of their reign that his upward progress achieved an almost unprecedented momentum and the second factor seems to have been a consequence of the first. The nature of his relationship to the Licinii is uncertain, but it seems likely that a common origin in the Etruscan region of central Italy at least predisposed Gallienus in his favour and he seems to have been that emperor's most trusted servant and adviser during the period of his sole reign - 260(?)-268 AD.
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 legatus Augusti pro praetore was the official title of the governor or general of some Imperial provinces of the Roman Empire during the Principate era, normally the larger ones or those where legions were based. Provinces were denoted imperial if their governor was selected by the emperor, in contrast to senatorial provinces, whose governors were elected by the Roman Senate.
Stratopedarchēs, sometimes Anglicized as Stratopedarch, was a Greek term used with regard to high-ranking military commanders from the 1st century BC on, becoming a proper office in the 10th-century Byzantine Empire. It continued to be employed as a designation, and a proper title, of commanders-in-chief until the 13th century, when the title of megas stratopedarchēs or Grand Stratopedarch appeared. This title was awarded to senior commanders and officials, while the ordinary stratopedarchai were henceforth low-ranking military officials.
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.
The tres militiae was a career progression of the Roman Imperial army for men of the equestrian order. It developed as an alternative to the cursus honorum of the senatorial order for enabling the social mobility of equestrians and identifying those with the aptitude for administration. The three posts, typically held over a period of two to four years, were Praefectus cohortis, Tribunus angusticlavius, and Praefectus alae.
Ancient Romeportal 
