HADRIAN'S WALL: THE ROMAN FRONTIER IN BRITAIN
by Mary M. Root
A wise military strategist, the Roman Emperor Hadrian (117-138 A.D.) realized the futility of trying to subdue the Celtic tribes. Successful Roman warfare depended upon a fight in open space, where waves of infantry could pound the enemy mercilessly. The forested hills and dales of Scotland favored Celtic guerrilla-tactics, especially ambush. Hadrian selected the limits based on the land’s topography: Hadrian’s Wall is a fortified boundary line.
Built in A.D. 122 by three Roman Legions, the Wall with its fortifications linked a series of turrets, garrison castles, and stationary, military camps along seventy-three miles of windswept moor. The Wall hugged the north rim of the River Tyne, thereby commanding the vicinity’s water supply and the hills above. Rather than Scottish forests, Roman sentries instead controlled the bleak and desolate moor stretching between the Irish and North Seas. The Roman surveyors and engineers traveling with Hadrian established the Wall’s position, maximized the use of local materials and talent in its speedy construction, and designed advantages for every Roman defender. "In pursuing its course from sea to sea, the Wall seldom deviated from the shortest and straightest course it could follow, and then only within the evident design of seizing neighboring elevations that would have otherwise commanded its position."¹
When first constructed, the Wall stood about 15 feet high, 10 feet wide at the base and seven and one half feet wide at the top. It is believed that an embattled parapet rose above the wall proper, to protect sentries on patrol. To the north a short distance a ditch averaging 25 feet in width and 10 feet in depth strengthened the defense. To the south, another ditch was created, with the excavated earth forming mounds along either side. Today this ditch is known as the Vallum, although the Roman word means "mound." The Vallum was the actual boundary line of Pax Romana and the official limit of the Roman Empire, and as such, was probably constructed first and used as an offset to the Wall, and for defense of the construction crews.
Local availability of materials counseled the Wall’s construction: stone was used for the 43-mile-long eastern portion and earth was used on the remaining 30 miles to the west. The stone blocks were generally 9 inches deep, 10 inches high, and ranged between 15 and 20 inches long. The stone faced an inner core composed of concrete and rubble. The earthen portion was an early example of cut and fill engineering; the Wall was formed with material excavated from the ditches.
It took three years to build the Wall and its fortifications. This was accomplished by three of the mobile forces known as a Legion. More than five thousand strong, a legion was an infantry force organized into ten cohorts, nine of them numbering about 500 men each. "The First Cohort was a special unit of almost double strength that included fighting troops as well as specialists and clerks of the headquarters staff. The ordinary cohort was subdivided into six centuries, or companies, each of which contained about 80 men under the command of a career officer, the centurian. Still smaller units were formed by the division of each century into 10 sections of eight men - contubernia, ‘tent parties,’ so called because in the field they shared a leather tent. On the march, each contubernium was provided with a mule, which carried the tent plus construction equipment. According to first-century AD historian Josephus, this equipment included a saw, a pickaxe, a sickle, a chain, a rope, a spade, and a large basket for moving earth."² Every legion included a body of specialized soldiers known as immunes; their skills earned them an immunity from routine duties. The list of immunes included architects, surveyors, plumbers, medics, stonecutters, water engineers, ditchers, blacksmiths and clerks.
The military surveyors, known as mensors, carried a Groma with them for laying out right angles, a decempeda (a 10-foot rod) for measuring short distances, a waxed cord or rope for measuring longer distances, a plumb line level known as a libra, and writing and drawing materials. The mensors were responsible for the overall position of the Wall, the stationing along its length of turrets, mile-castles, and forts, and the interior layout of each fort. To establish unerringly a line across Britain at just the point where the land was most narrow was quite an achievement. It is thought that the Roman surveyors performed the initial layout by lighting fires on hilltops, and "lining themselves in" along the lowlands. Once the line of the wall was established, the distances between structures were measured and marked. Turrets occurred every 1600 feet. These were small stone towers, thought to have been surrounded by wooden walkways. Turrets are sometimes referred to as signaling stations, but it is not known what devices or codes the Roman sentries might have been using. The "mile-castles"were established every 4,860 feet (a Roman mile), and were square fortresses housing a garrison of 32 men. In addition to patrolling the Wall, their duty was to protect the double gates that marked a crossing point between "civilized" and "barbarian" worlds. The stationary military camps were very large, and occurred along the Wall approximately every four miles. Here the mensors laid out a rectangular grid of streets, walkways and buildings. The layout was practical, military, and predictable. Soldiers hailing from many parts of the Empire could orient themselves wherever they found themselves stationed. The praetorium, or headquarters, was centrally-located. Around it were grouped the quarters of staff and bodyguard. Beyond this was a forum where the soldiers could meet, and again behind this the quaestorium, or paymaster’s office. Adjoining blocks contained the hospital, the foot-soldier’s barracks, kitchens, storehouses and granaries, workshops, stables, and baths. Yes, even in this remote outpost the Romans enjoyed the luxuries of plumbing. "There were centrally heated communal baths as well as latrines. The toilets consisted of wooden seats placed over a channel into which water could be poured to flush the waste into a refuse ditch. In the baths, furnaces heated bronze boilers that supplied steam and hot water. Besides cold or heated pools, the facilities frequently offered a dry-heat sauna chamber and a steam bath. They were focal points of the soldiers’ off-duty hours."³ There were other pastimes to fill the lonely posting: archeologists have uncovered remnants of board-games, drinking cups and flagons, letters written from home, and small shrines for worship.
The Legion surveyors were there to physically define the legal boundary of the Roman Empire. Once delineated, Hadrian’s Wall and fortifications represented the strength, stability and comfort of being a Roman. The Wall was Emperor Hadrian’s strategic solution to hostile terrain and intractable enemies. In time, he hoped to gain the northern territories, but not by force; Hadrian believed that the prosperity, goods and services of the Roman Empire would eventually accomplish more than its military might.
¹The Encyclopedia Britannica, 9th ed. (Philadelphia: J.M. Stoddart & Co., 1880) p. 326.
²Charlotte Anker, ed., Rome: Echoes of Imperial Glory, "Lost Civilization" Series (Alexandria, Virginia: Time-Life Books, 1994), p. 123.
³Ibid, pp. 135-136.
Birley, Anthony R. Hadrian: The Restless Emperor. New York: Routledge, 1997.
Dilke, O.A.W. The Roman Land Surveyors: An Introduction to the Agrimensores. New York: Barnes & Noble, 1971.
Quenell, Marjorie & C.H.B. Everyday Life in Roman and Anglo-Saxon Times. New York: Dorset Press, 1959.
Reid, T.R. "The World According To Rome," National Geographic Magazine, Vol.192, No.2 (August 1997), 54-83.