Ronen Schmitz Even Zur
Since prehistoric times, trade routes like the Lindenweg or Linienweg connected the Rhine-Main plain with the Usingen basin, which had been a centre of population since the Neolithic. Such routes would have followed a course from the mouth of the Nidda near Höchst, northwards across the low Taunus ridge, as does the modern Bundesstraße 456. A location along major communication routes almost always equals a strategic importance. Thus, it is no surprise that the mountain pass beside the Saalburg was first fortified by Roman troops during Domitian's wars against the Chatti (81-96 CE), when two simple earthen enclosures were erected (Schanzen A and B, located between the restored fort and the modern road).
Shortly after the two enclosures, around AD 90, a simple wood-and-earth fort was built to house a numerus. A numerus was a unit of auxiliary troops consisting of 2 centuriae and numbering about 160 men. There is some evidence that the troop stationed at this fort was a numerus Brittonum, i.e. a unit from Britain, but this is not entirely clear.
Late in the reign of Hadrian, c. 135 CE, the numerus fort was replaced with a much larger (3.2 hectare) fort for a cohort, a unit of about 500 men. The new castle was reoriented to face the growing Roman city of Nida (now Heddernheim). Originally, it had dry-built wood-and stone walls, which were replaced in the 2nd half of the 2nd century with mortared stone walls and an earthen ramp (147 × 221 m). The reconstructed fort is based on that third and last architectural phase, but reminders of the second phase are visible in the retentura (the back of the fort). Part of the second-phase defensive ditch has also been restored and can be inspected there.
The cohort fort was occupied by the Cohors II Raetorum civium Romanorum equitata (2. partially mounted Raetian cohort with Roman citizenship), a partially equestrian 500-men infantry unit, probably under the command of the legionary headquarters at Mogontiacum (modern Mainz). The cohort had initially been stationed at Aquae Mattiacorum (Wiesbaden), had then been moved to the Butzbach fort (ORL 14) and finally to the Saalburg.
The fort existed in that form and with that occupancy until the fall of the German limes in c. 260 CE. During the intervening period, the name of the unit is repeatedly mentioned in stone inscriptions, as are the names of some of its commanders.
In the early 3rd century, the situation along the limes became increasingly unsettled. A preventive war under Caracalla, who marched against the Alamanni and their Chatti allies from Raetia and Mogontiacum in 213 CE, lowered the Germanic pressure on the border only temporarily. The town of Nida (capital of the regional civitas) was given a defensive enclosure around that time. Already around 233, the Alemanni entered Roman territory again; further major incursions took place in 254 and 260 CE. Eventually, all areas east of the Rhine were lost during the major political and economic crisis of the mid-3rd century. In the course of these events, the Saalburg fort appears to have been abandoned deliberately and without military action.
After the abandonment of the Upper Germanic Limes, the fort was used as a quarry.