The Roman navy was an auxiliary branch of the army, a term applied to any military force that was not a legion. They were regarded as second-class soldiers as they were normally recruited from the non-citizen population of the provinces. Auxiliaries were paid 16% less than the men of the legions, and the fixed-term service was extended by a year to 26 years. It was not all bad, as the men that survived the 26 years were granted Roman citizenship on retirement.

The auxiliary part of the navy were the marine cohorts, and the ships' crews. Officers were civilians though it was also possible to find legionary officers placed in charge of marine cohorts. All officers above centurion and squadron commander were normally appointees from the upper classes.

Other auxiliary forces included all non-legionary foot soldiers, light skirmishers, archers and slingers, cavalry scouts and other specialist troops.

Just as in the Roman army, class was an important factor. Only those men of the highest social rank could hold the highest ranks in the Roman navy. All classes of freeborn citizens could rise to hold the other ranks, but as in the army, social barriers prevented promotion beyond the rank of Centurion. As the navy was regarded as an inferior service, there were few career soldiers to be found among its ranks.

Roman Navy Ranks

• The Praefecti ('Fleet commanders'): The command structure of the fighting men in the fleet was the same as in any legion. However, as the navy was considered to be an inferior service, it was considered beneath a Legate to command such a force; Legates were normally appointed from the Noble or Patrician class (the highest class in Roman society) or from the Senatores (the Senatorial class), the next class or level in Roman society. A commander of a fleet would normally be a Prefect because Prefects were thought to be more suitable coming as they did mainly from the lower Equestrian class Eques Romanus¹.

  So, Prefects were normally chosen from those of equestrian class who had some military experience, or they were simply appointed by the Emperor. The practice of appointing freed slaves of the imperial court² was employed because it assured the Emperor a measure of control over the navy. The appointments were largely political and almost all of the Prefects were totally reliant on the experience of their subordinates to command the fleets effectively. Within the rank of Prefect there were further ranks indicating the relative importance of the fleet they commanded and the amount they were paid annually.

• The Procuratores Ducenarii: This was the highest rank with an annual pay of 200,000 sesterces. It was the only rank to be placed in charge of the Praetorian Fleets, the Classis Ravenatis and the Classis Misenensis³.

• The Procuratores Centenarii: Although they commanded the fleets most likely to see action, the annual pay was much less, only 100,000 sesterces. Procuratores Centenarii were given the command of the Classis Britannica, the Classis Germanica and the Classis Pontica.

• The Procuratores Sexagenarii: This rank commanded an annual pay of 60,000 sesterces. The Procuratores Sexagenarii were given the command of the Classis Africana, the Commodiana Herculea, the Classis Moesica, the Classis Perinthia, the Classis Syriaca, the Classis Mauretaniae and the Classis Alexandrina; the other fleets listed would have received a similar rate, but may have been reduced according to the importance of the fleet.

Other Ranks

• Navarch ('Squadron commander'): This rank was also known as the Nauarchus and in later periods Nauarchus Archigubernes or Nauarchus Princeps. A Roman Squadron normally consisted of ten ships.

• Trierarch ('Captain'): The Trierarch was in command of all aspects of ship control while the vessel was not in action, giving direct orders regarding the ship and crew. The Centurion was in command of his men at all times; the Navarch had no direct authority over the milites⁴ or common soldiers.

• Centuriae ('Centurion' Military commander and Ship's Captain in Battle) The Centurion was in command of soldiers stationed on the ship. He was also in command of all aspects of ship control while the vessel was in action, giving the Trierarch direct orders regarding the ship and crew. Possibly the most dangerous rank in battle, as a good Centurion was an inspiration to his men. Traditionally, Centurions always led the men they commanded from the front, with a furious first-in-last-out style of leadership. Unsurprisingly, Centurions suffered high casualty rates constantly proving they were the bravest and the best of fighters.

• Optio Centuriae ('Optio centurion' A junior centurion) : The Optio's main duty in combat was to ensure that the commands of the Centurion were carried out especially in battle. In battle, if the Centurion was killed or injured, it was the Optio's duty to take command of the ship (or the 'century', as it was known, meaning 'the chosen'). Other duties included administration, casualty returns, equipment requisitions and supervision of training and punishment; for this he received twice the pay of ordinary soldiers.

• Cohors Classica ('A cohort serving at sea'): These men were also known as marines, but regarded as common soldiers or milites or milites classiarius to indicate they served at sea. Although these men were auxiliaries they were considered as inferior to land-based auxiliaries and men serving in the legions, and were the lowest paid of the auxiliary forces. They had to serve a year longer than a legionary to qualify for citizenship and a retirement allotment.

• Remiges⁵ (Rowers): The rowers or oarsmen were not slaves, they were freemen, or freeborn men from the provinces (Peregrini). They did not hold Roman citizenship and were paid a regulation wage. The Remiges were recruited from those provinces that had a seagoing tradition, so the crews were mainly Phoenician, Syrian, Egyptian or Greek. The ship's officer, the celeusta, was placed in charge of the rowers. To avoid many of the problems of training rowers to man ships with multiple banks of oars, basic training was carried out on land. The training was carried out on tiers of rowing benches set in huge frames, so by the time the rowers took their place in the ships for real, they were skilled enough to handle the oars and knew the commands.

The Immunes (Specialists)

• The Beneficiaries Classis (the quartermaster): Responsibilities of this class included the recruitment and welfare of the ship's civilian crew and the role of civilian paymaster. Other duties included procuring the ship's stores and ammunition, and supervising the ship's maintenance while in port.

• The Iatros (the medical officer equivalent to the army Capsarius a doctor or Medicus): The Roman navy had a very proficient medical service similar to that of the army and it remained unequalled for 1,400 years.

• Custos Armorum (Armourer): The Armourer's responsibility was the care and maintenance of the weapons and equipment of the Cohors Classica, and of the ship's ballista.

• The Nautae (Helmsman): Also known as the gubernator or pilot, the Nautae and his subordinates were given the task of steering the ship. Depending on the size of the vessel, it would have been equipped with either one or two linked sexillie (side-mounted) or quarter rudders mounted on the stern. If the ship was large enough there would have been a team of Nautae working in shifts while the ship was at sea. Often the Nautae would be provided with a shelter mounted on the stern. It is worth noting that the stern-mounted rudder did not appear until about 960 AD, long after the demise of the Roman Navy.

• The Proreta (Lookout): The Proreta worked in conjunction with the Naute while guiding the ship through shallow waters, or supervising the beaching of the vessel.

• The Celeusta (Officer in charge of the rowers): This officer supervised the rowers, relaying the orders of the avarch regarding speed and direction. The speed was governed by using a drum or hammer to provide the rowers with a rhythm to keep them in time and to control the speed of the ship.

Further ranks included The Fabri, trained wood and metal workers who maintained the ship. They were supervised by an officer called the Nav Phlax. There were also men who acted in a religious capacity, however there is no rank or title recorded for this group.