Drawing by Graham Sumner What you see is the Roman naval base at Velsen, just west of Amsterdam, which was in use during the reign of the emperor Tiberius. It is almost certainly identical to the fort named Flevum mentioned by Tacitus.

At the conclusion of the civil wars in 30 BC, Octavian had acquired fleets of his own and of his former enemies, totalling nearly 700 warships of all types, far more than could be afforded or, in the total absence of any opposition, would be needed. With the start of the Imperial period the whole concept of fleet organisation changed in parallel with the change in its role for the future. Having become a Roman lake, the Mediterranean and, increasingly, the Black Sea, had to be consolidated and policed. To do this, Octavian (now Augustus) and Agrippa established permanent, separate fleets, each with its own identity, commander, headquarters home base and defined area of responsibility. The system was to be formed around two main classes or fleets, based in Italy, with subsidiary fleets at strategic points around the Empire.

The first was the Classis Misenensis, based at Misenum at the northern tip of the Bay of Naples. Established by 22 BC, this was to be and remain the senior fleet of the navy and was ranked as praetorian, i.e. part of the emperor’s personal guard. The fleet’s area of operations was the entire western Mediterranean basin, but it could also (and did) project its power into the Atlantic and established a subsidiary squadron on the Mauretanian (Algerian) coast. This fleet was maintained at a strength in ships and men much greater than was strictly needed to perform its duties. As the senior fleet of the empire, it covered the western Italian coast and transported emperors, members of the imperial family and other notables; it also, importantly, acted as a training centre and a reserve of trained personnel for all branches of the service. These men could be and were sent to supplement other forces throughout the empire and even to provide the manpower for the foundation of other fleets. As an example, men from the Misene fleet were sent to establish the Classis Britannica in AD 43.

The Misene fleet remained the principal and strongest of the empire’s fleets almost to the end of the Western Empire. It was close enough to be able to be directed from Rome, as relay riders could deliver despatches between Rome and Misenum in one day. It was ideally positioned to be able to project its power across any part of the western Mediterranean basin, as well as to screen the ports of western Italy and the ends of the trade routes to the capital itself. The fleet had local facilities at various other ports and naval stations, for example at Cagliari (Carales), Civitavecchia (Centumcellae) and Aleria in Corsica. Ships were sent further afield from time to time, either for a particular mission or as a temporary detachment, inscriptions of members of the fleet having been found, for example, in Syria and Piraeus. There was a permanent detachment at Ostia and Portus, (when built); another was stationed at Rome, initially quartered in the praetorian barracks, but from the Flavians (later first century AD) until at least the mid-third century AD in their own permanent barracks in the city. There, one of their duties was to attend to the awnings that gave shade to the Colosseum.

The size of this fleet, and indeed that of all of the fleets, is unknown. The names of many ships of the fleet appear on grave stelae and votive altars and Nero was able to enrol a legion (approximately 4,500 men) from among the marines of this fleet in AD 68, later named I Adiutrix by his successor, Galba. At this time, it has been estimated, the fleet had over 10,000 sailors (whether this included marines is not said); at an average of 200 men to crew a trireme, this would indicate a fleet of about fifty ships. This is, of course, a very crude way of estimating numbers when considering a period of several centuries and a variety of ship types, each with differing crew numbers. Nevertheless, the base itself was the size of a town and the fleet establishment was many thousands of men deploying dozens and dozens of ships for most of its existence.

The second of the Italian fleets was the Classis Ravennate, established in about 23 BC at a new base built a short way south of the city of Ravenna, at the upper end of the Adriatic Sea. Slightly smaller than the Misene fleet, it was also rated as praetorian and had as its area of responsibility the Adriatic and Ionian Seas and, being adjacent to the mouth of the River Po (Padus), the navigation of that river system. This enabled the fleet to be a part of the protection of Italy north of the Apennines. The fleet could and did also operate around the Peloponnese and into the eastern Mediterranean.

Like the Misene fleet, a detachment from this fleet was stationed in Rome, again with their own quarters. The fleet’s harbour was one of the best on the Italian Adriatic coast, which has few natural harbours and the location also linked with the northern end of the Via Flaminia, a direct link to Rome. From their location, the fleet could provide rapid connections and communications with the north end of the Adriatic (through the port of Aquileia), to the eastern Alpine and upper Danube regions, or across to Split (Salonae), the Dalmatian coast (previously, with its myriad islands, a notorious haunt of pirates) and connections with the middle Danube area. In the south, stations were maintained at Ancona and Brindisi, the latter one terminal of the route to Durres in Albania (Durazzo, Dyrrhachium) connecting with the Via Egnatia through the Balkans to Thessaloniki (Salonica) and Byzantium (later Constantinople/Istanbul). There were two other stations in western Greece, to cover the Gulfs of Patras and Corinth and the Ionian Islands and passage along the western Peloponnese. Units of the fleet operated from time to time in support of the Misene fleet, especially in the third century AD, with frequent campaigns in the East.

Provincial fleets

Two other fleets were established for the eastern Mediterranean, the Classis Alexandrina and the Classis Syriaca. The former was to control the sometimes troublesome North African and Palestinian coasts and to oversee the increasingly important trade route, including grain transports, from Egypt to the West. The policing and regulation of traffic on the River Nile was the responsibility of the potamophylacia, a separate river police force organised by and inherited from the Ptolemies that had its own men, ships and bases on the river. This could be, and was from time to time, augmented by the fleet when needed; the potamophylacia was wholly absorbed by the fleet in the second century AD.

One other area of operations for this fleet was the Red Sea. The Romans did not maintain a permanent fleet on this sea, but did organise a fleet in 26 BC with personnel drawn from the Alexandrine fleet for a military expedition to what is now Yemen. This fleet had eighty warships and 130 transports, the latter being requisitioned local merchant ships. The warships, which in the absence of any anticipated opposition (there was in fact none) need only to have been of the smallest types, were ‘built’ on the Red Sea shore, presumably from prefabricated parts brought overland. Some were provided by the allied kings of Nabatea and Judaea, who also contributed forces for the venture. It is possible that the Nile-Red Sea canal was in use and that some of the ships could have been brought from the Mediterranean by this route. The canal was prone to silting if not constantly maintained; Trajan (ruled AD 98–117) restored the canal and with his annexation of the kingdom of Nabatea in AD 106, had both sides of the northern Red Sea under Roman control. Even so, there remains no evidence for any but occasional forays by the Alexandrine fleet on to the Red Sea.

The Classis Syriaca had its headquarters at Seleucia near Antioch on the north Syrian coast and was placed to cover the Levantine coast as well as the south coast of Asia Minor, also previously a notorious centre of piracy. The fleet also extended into the southern Aegean Sea and being the closest to the ever-present threat of Parthian and Persian power to the east, was instrumental in maintaining transport and communications links with the West, frequently having to transport troops to oppose threats or attacks from the east.

Although each fleet was a totally independent entity, their spheres of responsibility could and did overlap. Ships from separate fleets operated together seamlessly for differing operations, ships from other fleets being drafted to assist in major operations, such as the transport of troops and supplies for campaigns against the Parthians, or Trajan’s campaigns across the Danube.

The North African littoral of what is now Algeria and Morocco had been in a state of unrest and occasionally open revolt after the emperor Gaius (Caligula, emperor AD 37–41) had its ruler murdered. Under his successor, Claudius (emperor AD 41–54), the whole territory was brought under direct Roman rule in AD 41 and 42 and formed into the provinces of Mauretania Caesariensis (the eastern part) and Mauretania Tingitana (the western part). These campaigns were supported by the Classis Misenensis, augmented by ships of the Alexandrian and Syrian fleets. The capital of Caesarea (Caesariensis) received a naval base with its own harbour, distinct from the merchant harbour and which became home to a permanent naval detachment or squadron. This unit was made up from ships and men from the Alexandrine fleet, but was not constituted as a fleet in its own right, but remained an adjunct of its parent fleet, which was well able to supply the required ships and men as well as support, from the relative tranquillity of the eastern Mediterranean.

The squadron, although sufficient to patrol the coasts, including the Atlantic seaboard,, was not able to deal with major conflagrations and Misene ships had to intervene to suppress raiding by Mauretanians in AD 170 and 171. It intervened again in AD 260, to help suppress revolts in Africa and Numidia (part of modern Algeria). There were more peaceful interventions when naval personnel were employed to apply their abilities in civil works, for example, in AD 152, the engineer in charge of building an aqueduct at Saldae in Mauretania reported that ‘the constructor and his workmen began excavation in their presence, with the help of two gangs of experienced veterans, namely a detachment of marine infantry and a detachment of alpine troops…’

The expansion of the empire to the line of the Danube under Augustus, completed by 12 BC, engendered the formation of two more fleets for the defence of that river. The Danube was naturally divided into upper and lower parts by the Iron Gates Gorge (between Orsova and Donti Milenovac, about 100 miles (160 km) east of Belgrade), which was at that time an impassable torrent. For the new border adjacent to the provinces of Noricum, Rhaetia and Pannonia (approximately modern Switzerland, Austria and western Hungary), flotillas previously formed and used in the advance on the rivers Sava (Savus) and Drava (Dravus), were moved up to the Danube and reinforced to form the Classis Pannonica, with headquarters at Zamun, near Belgrade (Taurunum).