Britain had the largest army of any of the provinces of the Roman Empire. Scotland and Ireland remained unconquered, and unrest on the northern frontier was a permanent problem, despite the strength with which Hadrian’s Wall was held.
LEGIONS AND AUXILIARIES
The Roman army of the 1st and 2nd centuries was divided into legions and auxiliaries. The legions were battalions of heavy infantry, all Roman citizens, some 6,000 strong. Auxiliaries were non-citizen units, originally recruited from the warrior peoples that Rome had encountered in her frontier wars. They were valued for skills which the legions lacked, such as mounted warfare.
Auxiliaries were organised into cohorts of infantry and alae of cavalry, and many mixed units – usually 500 strong. On Hadrian’s Wall, for example, there was a cohort of Tungrians (raised in Belgium) at Housesteads, an ala of Asturians (from Spain) at Chesters, and a cohort of Dacians (from Romania) at Birdoswald. Auxiliaries were also raised in Britain, but these units always served outside their home province.
Unlike the legions, auxiliaries were not commanded by individuals of senatorial rank, but usually by young men of the equestrian order. Such men would have risen through the imperial service and were used to an aristocratic way of life which they attempted to recreate as best they could in Britain.
Roman Britain also had one of the great fleets of the empire, the classis Britannica, formed to patrol the Channel. Last attested in the AD 260s, it was based at Dover, Kent, where a Roman lighthouse still stands (within Dover Castle) as a reminder of the importance of this port in the period.
After the consolidation of the conquest, however, there was little military presence in the southern civil zone of the province. The army was permanently concentrated in the military landscape of the peripheral frontier zones in the north and west.
The bulk of the auxiliary army was stationed in smaller forts on Hadrian’s Wall or in the zone immediately south of it. The legions were based far south of the Wall in fortresses at York, Chester and Caerleon (in south Wales), although there were bases for outlying detachments on the northern frontier, such as Corbridge.
Housesteads, on Hadrian’s Wall, exemplifies the classic fort plan: a playing-card shaped rectangle, with a central range of buildings (the commanding officer’s house, headquarters and granaries) and barracks to the front and the rear. There are endless variations on this arrangement, however, and no two forts have identical plans.
Hadrian’s Wall and its forts were manned until the end of Roman Britain. From the 3rd century onwards, though, the fact that new kinds of fort were built along the south and east coasts of Britain shows that the prosperous south of the province was increasingly threatened by raids from the sea.
These ‘Saxon Shore forts’ reveal a new style of military architecture.
The first to be built, in the early 3rd century (such as Brancaster and Caister in Norfolk, and Reculver in Kent) were little different from the Hadrian’s Wall forts, with light defences and a neat rectangular shape. The later forts, however, built between about AD 275 and 300, have massive mortared walls, projecting towers and irregular circuits. There are immense surviving remains at Pevensey (East Sussex), Portchester (Hampshire) and Richborough (Kent).
Later still, after AD 370, there was an attempt to fortify the north-east coast south of Hadrian’s Wall with a series of small forts containing massive towers. Scarborough Castle in North Yorkshire contains the only visible example of these Yorkshire coast ‘signal stations’. Excavations have shown that the last garrisons of some of these posts were overwhelmed by attackers in the early 5th century.