Cohort (military unit)
A cohort (from the Latin cohors, plural cohortes, see wikt:cohors for full inflection table) was a standard tactical military unit of a Roman legion, though the standard changed with time and situation, and was composed of between 360-800 soldiers. A cohort is considered to be the equivalent of a modern military battalion. The cohort replaced the maniple following the reforms attributed to Gaius Marius in 107 BC. Shortly after the military reforms of Marius, each legion formed 10 cohorts. The cohorts were named "first cohort," "second cohort" etc. The first cohort gathered the most experienced legionaries, while the legionaries in the tenth cohort were the least experienced. Until the middle of the third century AD, 10 cohorts (about 5000 men total) made up a Roman legion.
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|Military of ancient Rome|
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first lieutenant /
|80–150||first lieutenant /|
|300–800||lieutenant colonel /|
|field army||100,000–300,000||general /|
|army group /
|2+ field armies||field marshal /|
general of the army /
|4+ army groups||field marshal /|
general of the army /
Originally, a cohort consisted of six centuriae, each commanded by a centurion assisted by junior officers. At various times prior to the reforms, a century might have 100 men. The cohort had no permanent commander; it is assumed that in combat the most senior centurion of the six would have commanded the entire cohort. In order of seniority, the six centurions were titled hastatus posterior, hastatus prior, princeps posterior, princeps prior, pilus posterior and pilus prior. The first centurion of the first cohort was called primus pilus.
During the reforms in the 1st century AD, the command structure and make-up of the legions was formally laid down, in a form that would endure for centuries. Standard centuriae consisted of 80 men each. The first cohort was made up of five double-strength centuries (160 men). The centurion of its first century automatically was the most senior in the legion and was known as the primus pilus. The primus pilus could be promoted to praefectus castrorum, (camp-prefect). The praefectus castrorum was in charge of the daily running of a legion.
These ranks followed the order of seniority in the earlier manipular legions, where the youngest and least experienced units were termed hastati, next principes, and the oldest and most experienced triarii (pilus was a rare alternative name for triarius, the singular of triarii).
The reformed legion numbered about 5,000 men, including officers, engineers and usually a small unit of cavalry (equites legionis; 120 men plus horses).
Types of cohort
- Cohors alaria: allied or auxiliary unit
- Cohors quinquagenaria: auxiliary, nominally 500 strong
- Cohors milliaria: auxiliary, nominally 1000 strong
- Cohors classica: auxiliary unit originally formed of sailors and marines
- Cohors equitata (LA): unit of auxiliary infantry with attached mounted squadrons
- Cohors peditata (LA): infantry unit
- Cohors sagittaria: infantry auxiliary unit of bowmen
- Cohors speculatorum (LA): guard unit of Mark Antony composed of scouts
- Cohors torquata (LA): auxiliary unit granted a torques (military decoration)
- Cohors tumultuaria (from tumultus, "chaos"): irregular auxiliary unit
Other Roman cohorts
Some paramilitary corps in Rome consisted of one or more cohorts, though none were part of a legion:
- The nine cohortes praetoriae, never grouped to a legion, the infamous Praetorians. The term was first used to refer to the bodyguard of a general during the republic; later, a unit of imperial guards (temporarily restyled cohors palatina (imperial cohort), c. 300 AD, under Diocletian's tetrarchy).
- Cohors togata was a unit of the Praetorian guard in civilian dress tasked with duties within the pomerium (sacred center of the capital, where all armed forces were forbidden).
- Cohortes urbanae, "urban cohort": military police unit patrolling in the capital.
- Cohortes vigilum, "watchmen": unit of the police force which also was the fire brigade in the capital.
- Cohors Germanorum (LA): the unit of Germani custodes corporis (imperial body guards recruited in Germania).
Furthermore, the Latin word cohors was used in a looser way to describe a rather large "company" of people (see, for instance, cohors amicorum).
- Goldsworthy, Adrian (2003). The Complete Roman Army. London: Thames & Hudson Ltd. ISBN 0-500-05124-0.
- "Hence adj. Pălātīnus -a -um Palatine; Apollo, whose temple was on the Palatine, Hor.; also relating to the imperial palace, imperial: Ov."—Simpson, D. P. (1968). Cassell's Latin Dictionary (5th ed.). New York: Macmillan General Reference. p. 420. ISBN 0-02-522570-7.
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