In Ancient Rome
Centurions were commander of Cohorts and proffesional officers in the Roman Army. In order to become a centurion, the soldiers had to be literate, have letters of recommendation, be at least 30 years of age and have already have served multiple years in the army.
A centurion usually commanded 83 men instead of the assumed 100.
There are no active centurions at the moment, and some are needed.