The urban cohorts (Latin:Cohors urbana) assume a triple role:guard of honor for the city of Rome in Roman antiquity, municipal police and also, military force.
Other cities under the Julio-Claudian dynasty are home to an urban cohort
* Ostia
* Puteoli
* Lugdunum
Timeline
* Created by Augustus in 13 BC. AD, the three urban cohorts owe their existence to his desire to counterbalance the enormous power of the Praetorian Guard in Rome. In the 2nd century, they came under the authority of the prefect of the praetorium, a figure whose power continued to expand. Augustus created the three cohorts in Rome, they are three in number, numbered from X to XII and number five hundred men each.
* Tiberius organizes them, in 23 AD. These soldiers are installed with the praetorians in the camp that the prefect Séjan had built.
* Upon the death of Caligula in 41, the urban cohorts attempt to play a political role, when the consuls and the Senate occupy the Forum and the Capitol with them in an attempt to restore the Republic. Senate splits and mob demands result in Claude's inauguration.
* Claude appears to increase the number of cohorts from 3 to 7.
* Vespasian reduces these units to the rank of fifty-year-olds and keeps only four.
* Vitellius seems to reduce the number of cohorts from 7 to 4. These, during the struggle between Vitellius and Vespasian, try to play a role similar to theirs in 41.
* Antoninus Pius seems to increase their number to 5 cohorts, including 1 detached outside Rome.
* Septimius Severus maintains the italic recruitment for these cohorts.
* Caracalla reduces the cohort number to 3 in Rome, 2 in Ostia and Puteoli.
* Aurélien had a barracks built for the urban cohorts of Rome, hitherto stationed at Castra Praetoria:Castra Urbana, at the Champ de Mars in the Agrippae Campus.
* While we know precisely the date of the suppression of the Praetorians (312), we do not know when the urban cohorts disappeared.
Organization
The hierarchy of the men, less known because of the gaps in the documentation, seems to be calculated on that of the courtroom. Each cohort is commanded by a tribune, most often a specialist in urban services who has passed through the tribune of security guards; he will then receive advancement by becoming a tribune of the praetorians. Below the tribune, at the head of the centuries, are placed six centurions who have generally served their apprenticeship in the legionary centurionates and the centurionates of the vigils; a certain number of these urban centurions came from the evocati Augusti. The non-commissioned officers (the main ones) are pretty much the same as in the line army. As in this one, they are divided into two groups, some detached to the prefect of the City of which they form the officium, the others serving in the body itself.
Organized on the type of praetorian cohorts, but without a cavalry contingent, the urban cohorts included 1,000 men per cohort, even 1,500 before Vitellius. Legal service time is twenty years, but the state can discharge a soldier before that term expires.
The recruitment of the urbaniciani seems close to that of the praetorians. Given the social background of origin, the links with the urban plebs must be very close and are recruited in their city. It is therefore difficult to admit that the task of repressing crowd movements has been entrusted to them. Occasionally, no doubt; systematically, it is unlikely. They therefore had a police role to reduce the crime that raged in the streets of Rome. Very occasionally, they could take part in a battle, but rather had an honorary role in the Roman army.