A frontier‐wall (see limes) of Roman Britain, running for 80 Roman miles (see measures) (118 km.; 73 mi.) from Wallsend‐on‐Tyne to Bowness‐on‐Solway. Erected under the governor Platorius Nepos c. ad 122–126, it was first designed to start at Pons Aelius, the eastern 67 km. (42 mi.) being in stone 3 m. (10 ft.) thick and perhaps 4.2 m. (13½ ft.) high, and the western 46 km. (31 mi.) in turf, 6 m. (19½ ft.) broad at the base and some 4.2 m. (13½ ft.) high. In front of the wall ran a V‐shaped ditch. Fortified gateways (milecastles), with towered gates to the north, occurred every Roman mile, and there were intermediate turrets (observation towers) every third of a mile. Milecastles and turrets continued to the west down the Cumbrian coast to St Bees Head. As construction progressed, changes came. The stone wall was reduced to 2.5 m. (7½ ft.) in width, and extended 6 km. (4 mi.) eastwards to Wallsend, and 6 km. westward (replacing some of the turf wall).
As planned, garrison forts (e.g. Vindolanda) remained behind the barrier on the Stanegate, the Trajanic road from Corbridge to Carlisle. At an early stage in construction the decision was taken to build a series of twelve forts astride the wall. After the decision to move forts onto the line of the frontier, the so‐called vallum was added to the south of the wall. The vallum was a flat‐bottomed ditch 6 m. (19½ ft.) wide and 3 m. (10 ft.) deep with the upcast disposed in two turf‐curbed mounds, one on either side, set back 9 m. (29½ ft.) from the lip of the ditch. This provided a continuous cleared area behind the forts along the full length of the frontier. Crossings were limited to causeways at the forts. Lateral communication was first supplied by branches from the Stanegate; only later did the Military Way, between vallum and wall, connect forts and milecastles. Before the end of the reign of Hadrian further forts were added to the system, bringing the garrison to c.9,090 men in auxiliary units.
After the accession of Antoninus Pius the frontier was advanced to the wall of Antoninus on the Forth–Clyde line. Hadrian's wall was rendered open to traffic by removing the gates from milecastles and filling in the vallum. In the 160s the wall was brought back into full use with the abandonment of the Antonine wall. There was extensive rebuilding and repair, but forts were reoccupied by units of similar size and type to those there before. Decreasing emphasis was placed on turrets and milecastles. The pattern so established endured for almost two centuries with only gradual modification, piecemeal rebuilding, and a slow decline in the size of the garrisons.
Subjects: Classical Studies.