For the lower Danube, from the Iron Gates to the Black Sea, the Classis Moesica was formed, with headquarters at Isaccea (Noviodunum) in Romania. This location is nearer to the Danube delta than the centre of the fleet’s stretch of the river because this fleet’s responsibilities extended into the western Black Sea and the sea routes between the river mouth and the Bosporus. With the increase of Roman power into and around the Black Sea area, the fleet acquired the further duties of protecting Roman interests in the western half of the Black Sea, including the Hellenistic cities around its northern shore and the strategic link with the Bosporan kingdom of the Crimea and adjacent lands, an important producer of grain. The fleet later established a naval base at Chersonesus.
To cover the southern shores of the Black Sea and to maintain a watch over its east coasts, the Classis Pontica was formed. The Romans had had some forces on the north coast of Asia Minor since they were organised by Pompeius in the sixties BC. The last client king of Eastern Pontus, Polemo II, was ‘retired’ in AD 63 and his kingdom annexed and made part of the province of Galatia. The former royal fleet was taken over and merged with the Roman ships to form the fleet, with its headquarters at Trabzon (Trapezus), later moved to Cyzicus (on the Sea of Marmara). For once there is a little evidence of the strength of this fleet, which was noted at some forty ships. This fleet extended its influence into the south-eastern Black Sea to eradicate the spasmodic piracy there and to cover the important military supply route from the Bosporus and Danube Delta, to north-east Asia Minor, to supply Roman forces facing Armenia and the Parthians. Subsidiary bases were set up in the second century AD near Poti (Phasis) in Georgia and Asparis, near the present-day Turkish-Georgian border.
The other great riverine frontier of the empire, the Rhine, also had its own fleet, the Classis Germanica. Caesar had established the border of the Roman Empire on the Rhine in the mid-first century BC, leaving garrisons with some small craft for patrolling, at intervals along its length. Legionary bases grew into towns at, for example, Mainz, Koblenz and Xanten. In 12 BC Augustus resolved to advance the border to the River Elbe (Albis) and in that year the future emperor Tiberius and his brother Drusus crossed the Rhine. Drusus concentrated the Roman’s existing ships and boats at Bonn and formally constituted them as the Classis Germanica, with its own praefectus and administration, as for the other fleets. He also had new ships built and brought trained crews from the Italian fleets by way of reinforcement. Fleet headquarters was at Cologne (Colonia Agrippinensis) and apart from the Rhine and Moselle, it was charged with patrolling and incursions into the tributaries entering from the right bank, such as the Neckar, Main and Lippe. Seagoing ships had to be acquired to cover the mouth of the Rhine and adjacent coasts. Later, with the addition of Britain to the empire, it had to operate jointly with the Classis Britannica to maintain the essential link between the armies of the Rhine and Britain. After the loss of the embryo province east of the Rhine after AD 9, the river became the permanent border, later altered from the middle reaches up by the advance into the Agri Decumates (the re-entrant between the Rhine and Danube) between the late first and third centuries AD.
After his conquest, Caesar had left ships on the north coasts of Gaul to patrol, deter any piracy and secure the trade in the English Channel. A few such ships under local military control had been sufficient for the predominantly peaceful area but in the forties AD Claudius resolved to add Britain to the empire. The ships were formally redesignated as the Classis Britannica and reinforced by new building and by ships with crews and specialist personnel brought around from the Mediterranean by sea. Preparations for the invasion had most likely, in view of their extent, started in the reign of Gaius, but were completed by his successor, whose forces invaded in AD 43. The new fleet was augmented by ships from the Classis Germanica and was vital to the success of the invasion which depended wholly on supplies from Gaul. After the initial invasion, the Classis Britannica had to continue to grow and extend its area of operations, as the Romans expanded their area of occupation, the fleet eventually operating right around the British Isles. The fleet’s prime purpose would remain however, to maintain the essential links with the mouth of the Rhine and the armies there, as well as with Gaul and the fleet headquarters was accordingly established at Boulogne and with another, a little later, at Dover (Dubris).
There were two other formations classified as fleets which do not seem to have been permanent, but pass briefly through the surviving records, indicating that they were formed for a particular purpose, at the ending of which they were disbanded. The first was the Classis Perinthia, formed by Claudius in AD 46 to cover his annexation of Thrace, after which there is no other indication of its continued existence. Thereafter responsibility for the Thracian coast passed to the Classis Moesica.
The other formation was the Classis Nova Libyca, which appears from the scant references, to have been formed in the late second century AD to reinforce the Libyan shores at a time of unrest there. It is not heard of again beyond the mid-third century AD and either was disbanded, it’s ships returned to their parent fleets, or was lost in the great upheavals of that time.
The late Empire
These nine imperial fleets continued to operate for nearly 200 years until caught up in the upheavals of the third century AD. With the Empire hard pressed by internal dissention and external pressure, the fleets could not be maintained as before, as the first call on available manpower, resources and money was the army. Neglected and denied resources, the great praetorian fleets deteriorated to a shadow of their former selves, as did the other Mediterranean fleets. The Black Sea was progressively abandoned and the riverine fleets seriously overstretched and at times overwhelmed.
With the accession as sole emperor of Diocletian in AD 285, stability was returned to the empire, together with the need to reorganise the remains of the fleets that he had inherited. The Classis Britannica, due to its particular location and function as a mainstay of the province’s garrison and defence and in the face of increasing barbarian seafaring activity and ability, had remained the least neglected and probably the best fleet left in the empire. It was part of the command of Carausius, commander in Britain, who improved its strength and efficiency and went on to the offensive against the sea raiders. It alone continued as recognisably the classis of yore.
The rest of the fleets in the Mediterranean were reorganised into a greater number of smaller squadrons, rather than try to reconstruct the great fleets. Each squadron was commanded by a praefectus and assigned to a military district and placed under the overall command of the military commander-in-chief for that district; in so doing the fleets lost their former independent identities as classes. Thirteen such squadrons were formed and became the basis of naval organisation in the Mediterranean thereafter.
The Danube border was reorganised into four new provinces, Moesia Prima and Secunda, Scythia and Dacia Ripensis. The former Classis Moesica was also divided into four parts, one allotted to each of the new provinces and again, under overall command of the local military commander. The fleet remained independent only insofar as that part of it based in the Danube delta and responsible for the Delta and with the Thracian coast. The Classis Pannonica disappears from the record in the third century AD, but Roman naval forces on the Upper Danube are known from the fourth century AD, once again as units forming part of the border forces, rather than as an independent fleet as before.
The Classis Germanica had all but ceased to exist by the mid-third century AD, local commanders having to employ whatever ships and crews they could acquire on an ad hoc basis. On the restoration of the Rhine frontier by the co-emperor Maximian after AD 286, naval forces were again built up but again on an area by area basis and allocated to local military commanders, the classis was not reconstituted as such.
These dispositions continued to serve through to the late fourth century AD, when with the loss of territory, including increasing parts of the Mediterranean seaboard, even the squadrons lessened in numbers, especially in the west until Roman naval forces were formed from whatever ships could be amassed and crewed.