Cohors III Ulpia Petraeorum

• Ulpia: Ulpian. The Imperial family name shows a link to the emperor Trajan (Marcus Ulpius Traianus). The unit was raised after the annexation of the Nabataean Kingdom in 106 AD, when parts of the Nabataean royal army were drafted by Trajan into six cohortes equitatae.[1]
• Petraeorum: from Petra or Arabia Petraea.
• sagittariorum or sagittaria: Archers.
• milliaria: 1000 strong. A Cohors milliaria peditata had a nominal strength of 800, a Cohors milliaria equitata of 1040.
• equitata: part-mounted.

The unit was a Cohors milliaria equitata with a nominal strength of 800 infantry (10 centuriae with 80 men each) and 240 cavalry (8 turmae with 30 cavalrymen each).

The cohort was raised by Trajan in the newly created province of Arabia Petraea and soon moved to Cappadocia to fight in his Parthian war.[2] The cavalry of the unit formed part of Arrian's expeditionary force in 135 AD, which he fielded against the Alans.[3] It remained part of the Cappadocian army until the end of the fourth century, since it is attested in the Notitia dignitatum as Cohors tertia Ulpia miliaria Petraeorum in 394 AD.[3]

Possible garrisons in Cappadocia were:[4]

• Metita: the Notitia dignitatum lists Cohors tertia Ulpia miliaria Petraeorum as stationed in Metita.

The following personnel is attested on diplomas or inscriptions:[5]

• Roman auxiliaries
• List of Roman auxiliary regiments

• Michael Alexander Speidel: The Development of the Roman Forces in Northeastern Anatolia. New evidence for the history of the exercitus Cappadocicus. in M. A. Speidel, Heer und Herrschaft im Römischen Reich der Hohen Kaiserzeit, Stuttgart 2009, Pages 596,618,621,625 (online)
• John Spaul: Cohors² The evidence for and a short history of the auxiliary infantry units of the Imperial Roman Army, British Archaeological Reports 2000, BAR International Series (Book 841), ISBN 978-1841710464