Hadrian's Other Wall

Emperor Hadrian (117-138) is well known for ordering the construction of the 70 mile stone fortification across the north of England, now known as Hadrian's Wall.  The wall was part of a large strategy of retrenchment, placing the Empire in a defensive posture for the first time since the founding of the Republic in 509 BC.  

Hadrian's immediate predecessor, Trajan (98-117) conquered Dacia (Romania) and annexed Armenia and Iraq.  The latter two overextended the empire's reach and Hadrian withdrew as well as relinquishing the plains of Romania to the barbarians while retaining the metal-rich uplands.

Shortly after his accession, Hadrian also prompted the erection of another wall, this time in Germany.  It was less ornate and permanent, being primarily a wooden palisade rather than stone structure.  It seems construction began shortly after Hadrian returned from the East to Rome in 118.  Some new details on the construction and its timing have recently come to light as described in Following Hadrian (the blog by Carole Raddato, who has spent years traveling through the former Roman world, retracing Hadrian's journeys).

After the defeat of Varus' legions in the Teutoberg Forest in 9 AD, the Romans had largely abandoned the east bank of the Rhine but during Domitian's reign (81-96) had reestablished a presence in what is now southwestern Germany, from the hills around modern Frankfurt and then heading southeast, encompassing most of the current state of Baden-Wurttemberg, until reaching the Danube in Bavaria.  While some fortifications had been built, it was under Hadrian that the system became organized and a physical barrier constructed.

 

Using the trunks of oak trees, the palisade stood up to 10 feet above ground.  The logs were pointed at the top and secured by cross beams.  The initial wall ran for about 50 miles between the Main and Neckar rivers - roughly from modern Frankfurt to east of Heidelberg) and it took about 1,000 trees per mile.

(Schematic of palisade, from Following Hadrian)

Watchtowers were constructed about every 1/2 mile along the wall and the entire section runs straight for the entire 50 miles.  Later emperors added to the barrier, eventually reaching 350 miles in length with 900 watchtowers.  

Wood is not as enduring as stone, so the initial palisade required rebuilding 50 or 60 years later.  The entire area was held until about 260 AD, when increasing pressures from the tribes forced the Romans to abandon the region and pull back behind the Rhine and Danube.

This video provides more information and, in its second part, a mini-tour of the entire barrier.

Ironically, it may have been the very presence of Rome on the borders of Germania that sparked the strengthening of the tribes and encouraging the incursions that eventually led to the fall of the Western Empire in the fifth century.  The Roman presence and increased trade led to greater wealth among the barbarians and a consolidation of formerly fragmented and constantly warring with each other tribes into great confederations like the Alemanni, Burgundians, Franks etc, as many of the tribal names from the 1st century disappeared by the third.