An auxiliary standard bearer, mid to late first century AD.
Note: The unit numbers given here are all ideal troop strengths and would have fluctuated during peace and war time.
These were units of non-Romans entirely composed of cavalry. The word ala means "wing" and was used
because of the cavalry's deployment on the wings of the army. It was here that cavalry was most effective at preventing the outflanking of the Roman battle line. There were two sizes of alae. The ala quingenaria was a unit of roughly 500 men. This unit was further divided into 16 units of roughly 32 men called turmae.
During the Flavian period additional, larger units of alae were created. The ala milliariae was a unit of roughly 1,000 men. Only a few of these existed in the empire. A province would have no more than one at a time. There were 24 turmae of about 32 men each.
Introduced in the Julio-Claudian period, these units were composed of a mix of infantry and cavalry. Julius Caesar and Augustus used mixed troops in this fashion, but only when the need arose. The permanent cohors equita did not appear until after. There were two principle sizes: the cohors quingenaria of roughly 120 infantry and 380 cavalry and the The cohors milliaria requitata of roughly 240 infantry and 760 cavalry.
Each legion had an attached unit of cavalry of probably 120 men. In the later empire the number is thought to have risen to around 760. It is not certain whether these units had an overall commanderapart form that of the legion. If it did, the post was probably filled by a centurio or perhaps an optio.
The Emperor and the provincial governors had cavalry contingents as body guards. Those protecting the Emperor were called equites singulares Augusti. This was the cavalry equivalent of the Praetorian Guard.
As seen in the above illustration. In use since the start of the Empire, they were more mobile than the heavily armored troops. made use of a lance, javelins and sword. They were effective at scouting, patrols, guarding the flanks and pursuing and cutting down a fleeing enemy. I don't know their name in Latin, and I am not sure if anyone does.
These heavily armored troop types were created under the reign of Trajan probably to counter the cavalry of the Sarmatian people. They carried the heavy lance (contus) which was developed from the Sarmations.
Cataphractii or Clibanarii:
These are 2 different words describing the same troops or possibly 2 types of heavy-armored cavalry. Completely armored from head to toe, this type was developed by eastern civilizations to counter the use of arrows. These troops appeared in Roman service probably under the reign of Hadrian (117-138AD).
The favored recruiting grounds for these horse archers were Crete, Vyrenaica Levant, Numidia, Thrace.
Note: This list is not complete. Though, it does contain the principle ranks and titles.
Praefectus Equitum: in overall command of an ala. Early in the empire this commander was a non-roman from the tribe of which his particular ala was composed. By the late 1st century AD the post was filled by a roman of equestrian status.
Decurio: in command of a turma
Officers below the rank of decurio were the prinipales and the immunes.
Prinipales were officers who could command small units of men and received higher pay than the common soldiers.
Vexillarius: in charge of carrying the vexillum, or battle flag. He was the highest ranked member of the immunes.
Imaginifer: carried a sculptural image of the emperor on a pole.
Cornicularius: secretary to the senior officer.
Duplicarius: 2nd in command to the decurio.
Sesquiplicarius: 3rd in command to the decurio.
Immunes received no extra pay, but they were exempt from certain the less desirable chores in the army.
Curator: the accountant.
Custos Armorum: custodian of the armor.
Actarius 2nd in command of the clerical and administration staff.
Strator a messenger.
Librarius a clerk.
Beneficiarius an assistant to the praefectus.
1. The Cavalryman, by Peter Connolly
2. The Roman Cavalry, by Karen R. Dixon
3. Auxilia of the Roman Imperial Army, by G. L. Cheesman
4. Roman Auxiliary Cavalryman: AD 14-193, by Nic Fields
5. Late Roman Cavalryman AD 236-565, by Simon MacDowall