Cohort (military unit) in the context of "Roman army of the mid-Republic"

Marcus Didius Julianus (/ˈdɪdiəs/; 29 January 133 – 2 June 193) was Roman emperor from March to June 193, during the Year of the Five Emperors. Julianus had a promising political career, governing several provinces, including Dalmatia and Germania Inferior, and defeated the Chauci and Chatti, two invading Germanic tribes. He was even appointed to the consulship in 175 along with Pertinax as a reward, before being demoted by Commodus. After this demotion, his early, promising political career languished.

Julianus ascended the throne after buying it from the Praetorian Guard, who had assassinated his predecessor Pertinax. A civil war ensued in which three rival generals laid claim to the imperial throne. Septimius Severus, commander of the legions in Pannonia and the nearest of the generals to Rome, marched on the capital, gathering support along the way and routing cohorts of the Praetorian Guard Julianus sent to meet him. Abandoned by the Senate and the Praetorian Guard, Julianus was killed by a soldier in the palace and succeeded by Severus.

The Marian reforms were putative changes to the composition and operation of the Roman army during the late Roman Republic usually attributed to Gaius Marius (a general who was consul in 107, 104–100, and 86 BC). The most important of these concerned the altering of the socio-economic background of the soldiery. Other changes were supposed to have included the introduction of the cohort; the institution of a single form of heavy infantry with uniform equipment; the universal adoption of the eagle standard; and the abolition of the citizen cavalry. It was commonly believed that Marius changed the soldiers' socio-economic background by allowing citizens without property to join the Roman army, a process called "proletarianisation". This was thought to have created a semi-professional class of soldiers motivated by land grants; these soldiers in turn became clients of their generals, who then used them to overthrow the republic.

Belief in a comprehensive scheme of reforms under Marius emerged in 1840s German scholarship, which posited that any changes in the Roman army between the times of Polybius and Marius were attributable to a single reform event. This belief was spread relatively uncritically and was accepted as largely proven by the 1850s and through much of the 20th century. There is, however, little ancient evidence for any permanent or significant change to recruitment practice in Marius' time. The occurrence of such a comprehensive reform led by Marius is no longer widely accepted by specialists; 21st-century scholars have called the reforms a "construct of modern scholarship".

The primus pilus (lit. "first maniple of triarii") or primipilus was the senior centurion of the first cohort in a Roman legion, a formation of five double-strength centuries of 160 men each; 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.

During the Roman Empire, the emperor Claudius created the office of primus pilus iterum. To become the primus pilus iterum an officer must have formerly served as a tribune in the vigiles, cohortes urbanae, or Praetorian Guard. The primus pilus iterum would hold the responsibility of a praefectus castrorum but with higher pay.

Vigiles or more properly the Vigiles Urbani ("watchmen of the City") or Cohortes Vigilum ("cohorts of the watchmen") were the firefighters and police of ancient Rome.

The draco ("dragon" or "serpent", plural dracones) was a military standard of the Roman cavalry. Carried by the draconarius, the draco was the standard of the cohort, as the eagle (aquila) was that of the legion.

The draco may have been introduced to the Roman army after the Dacian Wars by Dacian (see Dacian draco) and Sarmatian units in the second century. According to Vegetius, in the fourth century a draco was carried by each legionary cohort.

A signifer (Latin: [ˈsɪŋnɪfɛr]) was a standard bearer of the Roman legions. He carried a signum (standard) for a cohort or century. Each century had a signifer so there were 60 in a legion. Within each cohort, the first century's signifer would be the senior one. The -fer in signifer comes from ferre, the Latin for 'to bear' or 'to carry'.

The imaginifer was one of the signiferi in a legion of the Roman Empire who carried the imago (the image) of the emperor.

The imaginifer was added to the ranks of the legions when the imperial cult was first established during the reign of Augustus. The image was a three-dimensional portrait made from beaten metal. It was carried only in the leading cohort.