From its inception the fleet was a consular command. Under the Roman Republic, two magistrates were appointed each year, the consuls, who were the supreme officers of the Republic and who led the army in the field and also therefore, by extension, the naval forces. The weakness of the system was that a consul only served for one year in office and there was thus no continuity of command. To alleviate this problem, especially once Roman forces’ operations became more widespread, a consul, on retiring from office could be appointed as a proconsul and could continue in command, as indeed could other ex-consuls, (always under the aegis of the current consuls) all of whom by definition were senior, respected and with any luck experienced and competent officers.
The consul, as supreme commander, appointed military tribunes to be his subordinate officers, from among officers having five to ten years experience of military service. The tribunes in due turn appointed centurions to command each century of fighting men and centurions appointed an optio to be their lieutenant.
In the early days, with just a small number of ships acquired and operated in an ad hoc way, the navy was seen as little more than an adjunct to the army, whose command structure was adequate to handle them. Thus a consul could appoint a tribune to command the ships, who in turn appointed officers to command each ship. There is no evidence of the manner of organisation of these earliest naval forces but these assumptions are made from known military practice. No doubt the system evolved further by itself in a way dictated by practical considerations, but by 311 BC, it had proven insufficient to furnish adequate and efficient naval forces.
In that year two officers, the duoviri navales were appointed by the Senate. These were senior appointments, charged with providing, equipping and keeping in repair a fleet. In short they were a ‘board of admiralty’ responsible for the administration of a navy, a service which thereupon became in fact distinct from the army. Operations remained the province of the consuls and their officers, but were tempered by the navy’s own officer corps. The navy could now operate in an organised fashion: dedicated shipyards for building and repairs could be provided; stores for all the paraphernalia that the ships required could be set up and stocked; provision for the proper laying-up and maintenance of ships during the winter closed sailing season could be overseen; victualling could be arranged and suited solely to the requirements of the ships.
In 267 BC, just before the outbreak of the First Punic War, four praefecti or fleet prefects were appointed and entitled quaestores classici, quaestors of the fleet, presumably in addition to the duoviri and each was posted to a particular area, one at Ostia at the mouth of Rome’s river, the Tiber and one in Campania, the Bay of Naples area; the locations of the other two are not known (after the War, one was posted to Marsala in western Sicily). It is clear that while the duoviri continued to handle the central administration of the navy, the praefecti dealt with the operation of the squadrons of ships in their respective areas, including the organising of local facilities for the building, repair and victualling of ships and the housing and training of their crews. They thus expanded and built upon the start made by the duoviri over the preceding forty-four years. This basic infrastructure would be of increased importance in the expansion of the service towards the Punic Wars period, especially with the influx during that time of greater numbers of non-citizen recruits. The size and scale of fleets and operations in this war, far beyond the Roman’s previous experience, demanded more diversity in command structure and from 264 BC, the Senate could appoint a praetor to command a detached squadron; this was a senior rank, equivalent to that of a governor of a province, for which a man of the senatorial class was required, unlike the tribuneship which drew its men from the lesser equestrian class. These commissions would only last until the end of the particular mission for which it had been granted.
This command structure worked well throughout the First Punic War, operational command of the fleets at sea remaining with the consuls and their tribunes. For the wider-ranging Second Punic War, in addition to the main fleets in Italy, other fleets were sent for service in Spain and Greece. As before, command of these detached forces was entrusted a praetor, such as Marcus Valerius Laevinus, who was sent in 214 BC, with twenty-five ships to Brindisi to assume command of the forces there and support Rome’s allies in the First Macedonian War.
This system remained unchanged until the war against the pirates waged by Pompeius in 67 BC. Pompeius divided his intended area of operations, in effect the whole Mediterranean, into thirteen sectors and appointed a legatus to each as its overall military commander for sea and land forces. A legatus (legate) was the rank to command a legion. Eleven more were appointed for the forces Pompeius had with him and in addition, he appointed a praefectus classis et orae maritimae (prefect of the fleet and the coast). Nothing further is heard of the duoviri and praefecti and perhaps their office and functions were merged with or subordinated to that of the new praefectus. This would seem unlikely as the newly created appointments are not mutually exclusive. The existing administration system had matured and worked well and it was the neglect and consequent weakness of the navy that had permitted the growth of piracy, rather than any failing in its organisation. As the navy continued to function after the war against the pirates and no more is heard of Pompeius’ special appointments, it must be concluded that the extra appointments were provided for that purpose only and that the former organisation continued afterwards. While at the close of these operations, surplus ships were laid up and the extra forces recruited for them were stood down, permanent squadrons were kept in commission and posted to various areas, each continuing to be commanded by a legate.
Imperial high command
After 30 BC a new high command structure was adopted reflecting the division of the service into various permanent fleets. There was no centralised navy high command although a staff officer from each of the Italian fleets was with the military staff attending the emperor, together with a staff officer from any of the other fleets in whose area the emperor might be. All responsibility for command of each fleet and everything to do with it was vested in the praefectus classis (fleet prefect), who was appointed by and answered to the emperor; the duoviri navales were dispensed with. Given the distances and the time that communications took at that time, this was the only practical method for the command of widely separated forces. The command of each of the two Italian fleets was entrusted to a praefectus appointed by the emperor and of at least equestrian rank and rated equivalent to Praetorians, i.e. guards; these posts would be held by ex-legionary tribunes and under Claudius by imperial freedmen. The consular and senatorial appointments ceased. Provincial fleet commanders, again appointed by the emperor, but under the local overall command of the provincial governor, were now also classified as praefectus classis. Under the praefectus was his subprefect as executive officer and aide-de-camp, a cornicularius as next-ranking officer and a number of functionaries who were probably leading rankers rather than officers, of various types, called beneficiarii (appointees), actuarii (clerks), scribae (writers) and dupliciarii (this last as senior or leading ratings, on double pay), all of whom made up the Prefect’s administrative or office staff. One position from Republican times that was continued into the Imperial navy was that of quaestores classici for each fleet: a quaestor was primarily a financial officer, hence these were fleet treasurers.
Claudius replaced the fleet prefects, traditionally of equestrian or even senatorial rank, with appointees who were professional bureaucrats, with procurators who were usually imperial freedmen, i.e. ex-imperial slaves and non-military men. Vespasian (emperor AD 69–79) reverted to the appointment of experienced military men. The Italian fleet prefects were now second in rank only to the Praetorian prefect, and once more of at least equestrian class.
These command structures continued through the time of chaos in the third century AD, when much of the navy itself ceased to exist. The naval forces that survived continued to be commanded by a praefectus for each of the squadrons that succeeded, each based on a local centre under the overall command of the dux, a new rank for the overall district military commanding officer. There were thirteen such squadrons but no indication that social rank was a continuing requirement for senior officers. A further rank was added from the third century AD, namely that of praepositus reliquationis; this was a temporary flag rank for an officer commanding a detachment or in the absence of the praefectus rather in the manner of the old republican appointment of a praetor for a similar purpose.
The emperor Constantine greatly reformed the armed forces, in most cases appointing local area commanders who had both troops and fleets under them and with no separate naval command, high or otherwise. Senior military officers in the late period of the Empire were rated as magister militum or magister equitum (for cavalry) but there is no record of a magister classis and fleets continued to be commanded by praefecti, who were again subordinate to their local duces or military commanders. The exception was probably the British Fleet which retained more of its old, early empire structure, due to its particular area of operations in that the ‘frontiers’ of the province were of course, mostly sea. In AD 364 there is a mention of a comes maritimae’in Britain, a supreme naval commander, but this is the sole mention of this post and it may well be a one-off commission for a particular purpose.
For the remaining life of the Imperial navy it seems that military commanders were appointed largely on a provincial basis to include whatever naval forces fell under their sway, there being no mention of any separate ranks that refer to naval forces alone. Roman naval squadrons enjoyed a brief resurgence in the early fifth century AD, before being finally lost in the abortive attack on Vandal-held Carthage in AD 467. No details survive of the organisation of these last Roman fleets, the command of which resided with the military commander of land forces, appointed by the emperors and there is no record of a strictly naval command structure, beyond the captains of individual ships.