This word (cohors) was originally applied to the divisions of the
Italian allies in the
Roman army, and consisted of 10k
infantry of a) 20
cohortes of 420 men each : the
cohortes alares, who formed the wings (alae) of the two
legions, and b) four select cohortes of 400 men each. The Roman legion numbered ~4k men, and was divided into ten
cohortes, each containing three
manipuli or six
centuriae.
Auxiliary troops were later divided into
cohortes auxiliariae, which contained either five or ten
centuriae.
Those troops stationed in
Rome were also numbered by
cohortes:
- The cohortes praetoriae were the imperial bodyguard formed by Augustus, who were first nine, then ten in number. They were once formed of cavalry; later, infantry.
- Three (and later four) cohortes urbanae, of 1000 men each. They ranked below the bodyguard and out-ranked the legionaries.
- Seven cohortes vigilum of 1000 men each who formed the night police and fire brigade - one to every two of the 14 regiones.
Cohort should not be used in place of partner (in crime), or in any case where it refers to one person. I'll fight this 'til the end.