This is intended to identify officers of the Roman army who were given commands that were normally reserved for men of senatorial rank as part of their cursus honorum. Most of the beneficiaries of such promotions are likely to have been ex-centurions who had achieved the rank of primus pilus and thus entered the equestrian order. By a decree of the Emperor Gallienus such officers could be given the command of legions, a position formerly reserved for senatorial legati Augusti. This reform marked a watershed in the organisation of the Roman Army and in Roman social history.

The category 'Equestrian Commanders of Vexillationes' does not exclude men who went on to achieve senatorial status - or even to become emperors. The distinguishing feature of this category is that, while still of equestrian status, they became commanders of legions and governors of garrisoned provinces, posts previously reserved for senators (except in the case of Egypt or Mesopotamia). Officers serving as Duces would invariably have been of this category.