Hadrian’s deep concern with consolidating and defining the Empire started very early in his reign. Upon ascending the throne, the new emperor abandoned Trajan’s newly conquered provinces beyond the Euphrates and rapidly took the opportunity to carry out his new frontier policy. He first embarked on a quick inspection of the military bases along the lower and middle Danube frontier on his way back to Rome (see post here) and then turned his attention to the Rhine frontier.
Hadrian started his consolidation of the military frontier fortification in Germania Superior with the construction of a timber palisade which linked two rivers, the Main and the Neckar on the Wetterau and Odenwald Limes. The similarities between this linear barrier and a comment in the Historia Augusta is rather striking:
“[…] in many regions where the barbarians are held back not by rivers but by artificial barriers, Hadrian shut them off by means of high stakes planted deep in the ground and fastened together in the manner of a palisade.” HA Hadr. 12.6
No province is mentioned by name, but the Historia Augusta passage appears in the context of Hadrian’s first visit to the German provinces as emperor in 121-2 and matches what has been found in Germany. However, Hadrian’s visit to Germany and the construction of the limes palisade may not have been contemporary. During excavations in 2002/2003, remains of a waterlogged stretch of palisade were uncovered at Marköbel near the site of Watchtower 5/1. The felling dates of the trees were established by dendrochronology (tree-ring analysis) as the winter of AD 119 and the summer of AD 120. This was the first time that the palisade on the Upper German Limes could be securely dated.
The ancient literary source, which attributed the building of artificial frontier-works to Hadrian, was therefore confirmed. However, it was widely assumed that Hadrian ordered the construction of the frontier palisade during his tour of Germany in AD 121-2. Instead, the dates obtained by dendrochronology would suggest that the army anticipated the emperor’s arrival, allowing Hadrian to inspect the work in progress (Schallmayer 2003). This is seemingly plausible as Hadrian served in the province as military tribune twenty-two years earlier and would have been familiar with the military situation in the area.
Initially, the limes consisted of a patrol path cut through the forest and overlooked by wooden watchtowers. In Upper Germany, the first phase of its development is dated to Trajan’s rule (c. AD 100) with a series of new forts established on the edge of the Wetterau region as well as further south along the Main river, in the Odenwald and along the Neckar river. This kind of open boundary was no real obstacle for raiders and allowed an uncontrolled traffic of commercial goods. Around AD 119-20 a continuous palisade was added along the border on the orders of Hadrian.
The palisade consisted of trunks of oak trees, split in half and set side by side in a foundation trench 1 to 1.5 metre deep. It stood up to 3 metres above ground. The logs, up to 50 cm in diameter, were pointed at the top and secured on the inside by cross beams to hold them in place and prevent the extraction of individual poles by the enemy. According to the diameter of the surviving trunks, the timber was taken from oak trees about 100 years old. In Upper Germany, the Hadrianic palisade ran continuously for 81 kilometres, highlighting the environmental cost of this new frontier. Some 700 trees were needed to build a single kilometre of limes palisade.
Behind the palisade stood watchtowers, used to observe anyone approaching the frontier and send messages to soldiers in the nearby forts. Forts along the frontier were 10 to 30 km apart, so there was no inter-visibility between forts. The towers, however, stood about 700 m apart so that communication between towers was possible. Those of the earlier Roman Empire were mainly constructed of timber and were later replaced by stone constructions. Roughly 900 watchtowers were constructed along the 550 kilometre-long Upper German-Raetian Limes. The wood and stone towers were mainly square in plan and had sides measuring between 3 and 6 metres, suggesting a height of between 7 and 10 metres. Depictions on ancient monuments such as the Trajan and Marcus Aurelius columns in Rome show how the limes palisades and watchtowers actually looked.
The Hadrianic palisade at Marköbel was never replaced (timber lifespan is believed to be between 50 and 60 years), but about AD 170, a c. 6m wide and 2m deep ditch was cut, with an earth mound behind it, creating an obstacle called the Pfahlgraben. The assumption, prevailing until recently, that palisade, earth mound and ditch existed simultaneously thus turned out not to be true in Upper Germany (Schallmayer 2003). The wooden palisade was probably abandoned due to lack of wood. Since the Roman had an enormous demand for timber for the erection of palisades, towers and forts, it would be reasonable to believe that wood had become in short supply by the end of the 2nd century AD. The latest phase of development on the limes in Upper Germania has been dated by a series of inscriptions and dendrochronological analysis to AD 160 and to ca. AD 200 in Raetia.
Kastell Marköbel was a fort occupied by a cohort, a unit of about 500 men. Initially a wooden fort constructed under Trajan around AD 100, it was replaced under Hadrian with a slightly larger (3.21 hectare – similar in size to Saalburg) fort built in stone. The porta decumana (back door) and the porta principalis sinistra (left side gate) were uncovered in 1892 and 1893 by the Imperial Limes Commission. Further excavations in 1983 revealed evidence of a previous building in wood and earth construction, which was aligned under the wall of the stone fort. The fort was surrounded on all sides by a double-pointed ditch, the inner one with a width of 9 m, the outer with a width of 11 m and a depth of 2 m. The layout of the fort can still be seen in the townscape.
Hadrian’s palisade was also a mean of keeping the soldiers fit and active (Birley, 1997). His biographers offer a rather detailed account of the military measures and reforms that Hadrian was to take during his subsequent inspection of the German frontier in AD 121/2. We read in Cassius Dio’s biography that Hadrian had forts moved to more favourable sites, abandoned some and founded others. The HA biographer adds that Hadrian insisted on reinvigorating discipline among the soldiers, but also on living with the troops, sharing their basic military diet, and eating, like them, in the open.
Hadrian travelled through one province after another, visiting the various regions and cities and inspecting all the garrisons and forts. Some of these he removed to more desirable places, some he abolished, and he also established some new ones. He personally viewed and investigated absolutely everything, not merely the usual appurtenances of camps, such as weapons, engines, trenches, ramparts and palisades, but also the private affairs of every one, but of the men serving in the ranks and of the officers themselves, — their lives, their quarters and their habits, — and he reformed and corrected in many cases practices and arrangements for living that had become too luxurious. Cassius Dio, 69, 9
Though more desirous of peace than of war, he kept the soldiers in training just as if war were imminent, inspired them by proofs of his own powers of endurance, actually led a soldier’s life among the maniples, and, after the example of Scipio Aemilianus, Metellus, and his own adoptive father Trajan, cheerfully ate out of doors such camp-fare as bacon, cheese and vinegar. And that the troops might submit more willingly to the increased harshness of his orders, he bestowed gifts on many and honours on a few. For he re-established the discipline of the camp, which since the time of Octavian had been growing slack through the laxity of his predecessors. HA Hadr. 10.2-3
The Upper-German-Raetian Limes marked the border between the Roman Empire and Germanic tribal territories from the end of the 1st century AD until about AD 260. During the generally peaceful period of the 2nd century AD, there was bustling trade and fruitful cultural exchange between the Germanic tribes and Romans. The limes was not so much a military stronghold, but rather a guarded boundary line, where traffic could be controlled and goods traded or customs charged on them. This border control worked successfully until the middle of the 3rd century AD when its demise was brought about by increasing Germanic threats and internal conflicts in Rome.
Rome’s German frontier runs for almost 550 kilometres from the Rhine near Rheinbrohl to meet the Danube at Abusina west of Castra Regina (Regensburg), boasting numerous small forts and over 60 large forts for cohorts and alae (Roman allied military units), 80 fortlets and over 900 towers. Today, the limes in Germany represents the longest archaeological monument in Central Europe. Since 2005 the Upper German-Raetian Limes (ORL) and Hadrian’s Wall in Great Britain form the international UNESCO World Heritage Site Frontiers of the Roman Empire, with the lower limes in the Netherlands being placed on the tentative list in 2011, aiming to extend the world heritage site to the whole limes.
The Deutsche Limes-Straße, founded in 1996, created a touristic route for motorists and later on created the Limes Cycle Route, encompassing more than 70 towns and villages along the path, with a whole collection of excavation sites, forts, reconstructed towers and museums. The best preserved section of the Roman frontier is found in the Taunus where visitors can see reconstructed watchtowers and forts of varying size, including the reconstructed Saalburg and Pohl forts.
Sources & references:
- Egon Schallmayer, Der Limes, Marköbel und Kaiser Hadrian. Neue wissenschaftliche Ergebnisse zum Obergermanisch-Raetischen Limes und ihre öffentlichkeitswirksame Präsentation. In: Denkmalpflege und Kulturgeschichte 2, 2003 S. 12–21.
- Breeze David J., (2011). The Frontiers of the Imperial Roman Empire. Pen and Sword Books. pp. 56-61
- Birley, Anthony R., (1997). Hadrian. The restless emperor, Routledge London New York pp. 113-122
Image header by Haselburg-Müller (Wikipedia)