Cohors I Aelia Dacorum

Cohors I Aelia Dacorum

Roman infantry helmet (late 1st century)
Active AD 117-25 to c. 400
Country Roman Empire
Type Roman auxiliary cohort
Role infantry
Size 800 (until AD 284)
Garrison/HQ Britannia AD 125 - c. 400

Cohors prima Aelia Dacorum ("1st Aelian Cohort of Dacians") was an infantry regiment of the Auxilia corps of the Imperial Roman army. It was first raised by the Roman emperor Hadrian (r. AD 117-38) in the Roman province of Dacia not later than AD 125 and its last surviving record dates c. 400. It was deployed, for virtually its entire history, in forts on Hadrian's Wall on the northern frontier of Britannia province.


The regiment carries the epithet Aelia, implying that it was either founded, or honoured for valour, by the emperor Hadrian (Publius Aelius Hadrianus).[1] It was probably founded between AD 117 (the date of Hadrian's accession) and c. 125, the date of the unit's first datable attestation.[2] The Dacorum name suggests that its initial recruits were mainly ethnic Dacians from Moesia and/or the recently conquered Roman province of Dacia (annexed in 106 by Hadrian's predecessor, Trajan). As no record of the unit has been found in Dacia, Holder argues that the regiment was transferred to Britain immediately after it was established. (This was in accordance with a general imperial policy of deploying auxiliary units far from recently conquered (or pacified) regions in order to assure their loyalty: thus, 7 British regiments, raised during the Flavian period (71-96), are attested as deployed in Dacia in the reign of Hadrian).[3]


The regiment was probably of milliaria strength i.e. 800-strong, divided into 10 centuriae of 80 men each. Although only one of its records mentions its milliaria status, the latter is supported by the fact all but the first of its attested commanders carried the title of tribunus, normally an indication of milliaria status.

The fact that the unit's first surviving record (c. 125) attests a Cohors I Dacorum (without the Aelia title), and that its commander at the time, Marcus Cludius Severus, held the rank of praefectus, has led to the suggestion that it was originally a quingenaria regiment (480-strong, divided into 6 centuriae) and that it acquired its Aelia title when it was upgraded to milliaria status in 127.[4]

There is no evidence that the unit ever acquired a cavalry contingent: in no inscription is the regiment ascribed the epithet "EQ" (for equitata = "equipped with cavalry"), and no cavalry officer (decurion) or trooper (eques) is attested.[4]


Partial view of excavated remains of Roman Fort Banna (at Birdoswald, Cumbria, England). Cohors I Aelia Dacorum was stationed here for at least 150 years until AD 276, and probably for about a century thereafter
View of the remains of Hadrian's Wall (right, stretching into the distance), as seen from Fort Banna. Originally, the wall was c. 5 m (16 ft) high, but stone removal over the centuries has reduced its remains, at this point, to barely 2 m

The regiment was transferred from Dacia to Britain not later than 125, when it was stationed briefly at Fort Fanum Cocidi (Bewcastle, Cumbria) and appears to have participated in the excavation of the so-called Vallum, a huge ditch running along the near side of Hadrian's Wall (constructed 122-8). It was permanently stationed at Fort Banna (Birdoswald, Cumbria), on Hadrian's Wall, from 126 to at least 276/82, where it is attested in numerous inscriptions.[2]

The inscription of 276/82 is the latest datable record found which mentions I Aelia Dacorum. However, a later inscription found at Fort Banna, datable to the latter period of the emperor Diocletian's rule (293-305), records that the fort's headquarters buildings, which had fallen into ruins, were rebuilt under the direction of the centurion Flavius Martinus, who is described as praepositus cohortis ("cohort acting-commander"). The fact that the fort was in ruins and then repaired suggests that it may have been abandoned for a period, and then re-occupied. But because the text is incomplete, it is uncertain whether Martinus commanded I Aelia Dacorum, or some other regiment.

The regiment is recorded in the Notitia Dignitatum, a late 4th-century official document which contains a list of Roman military units in existence around AD 400, as stationed at Camboglanna (Castlesteads, Cumbria), the fort on Hadrian's Wall neighbouring Banna to the east.[5] This record shows that the regiment was probably present in Britain until the definitive withdrawal of Roman troops from the island in c. 410. By this time, the unit probably contained only c. 300 effectives, around a third of its size in the 2nd century. This reduction was in line with the army in Britain as a whole, which had shrunk from a peak of c. 55,000 in 200 to c. 17,500 effectives in 400.[6]


In view of its size and long-term stationing on the northern British frontier, facing the unconquered Caledonia (Scotland), the regiment almost certainly participated in all the major campaigns recorded in this turbulent region, including:


The epigraphic record shows that, during the 2nd and 3rd centuries, the regiment won 5 more imperial titles, presumably for valour, or for loyalty to the awarding emperor:[11]

  1. Antoniniana: this title, attested in an inscription dated 218-22, could, in view of the name, have been accorded by Antoninus Pius, Marcus Aurelius Commodus or Septimius Severus. However, it appears that in 212/3, several regiments in Britain were accorded the title. Frere argues that these awards were made by the emperor Caracalla (M. Aurelius Severus Antoninus, r. 211-17), in order to secure the British regiments' loyalty after the assassination of his brother and co-emperor Geta, who enjoyed wide popularity in the army.[12]
  2. Gordiana (Gordian III r. 238 )
  3. Postumiana (Postumus r. 260-9)
  4. Tetriciana (Tetricus I r. 269-74)
  5. Probiana (Probus r. 276-82)

The awards show that, in the period 260-74, the regiment gave its allegiance to the "Gallic" emperors Postumus and Tetricus I, who ruled the breakaway western section of the Empire (comprising Gaul, Spain and Britain), known as the "Gallic Empire".

Religious cults

Of the 27 stone altars found at the cohort's long-term fort (at Birdoswald, Cumbria), 24 are dedicated to Jupiter, the highest Roman god, originally the supreme sky-god of the Indo-Europeans. These are headed with the initials "IOM", for Iovi Optimo Maximo ("to Jupiter the Best and Greatest"). One of these was jointly dedicated to Jupiter and to the numen ("Divine Spirit") of the first emperor Augustus, who was officially deified after his death. One altar is dedicated to the Roman god of war Mars and one to the god of the sea, Neptune.

Only one altar was dedicated to a native British deity, the Celtic god Cocidius (after whom the fort occupied by the cohort before Banna was named: Fanum Cocidi, meaning "Shrine of Cocidius", at Bewcastle, Cumbria).[13]

However, these dedications are in no way representative of the religious affiliation of the regiment's members, as they were all erected by the cohort's tribunes (commanding officers). They thus represent the army's official cults. The cohort's soldiers doubtless revered a great variety of British and other native deities.

Attested Personnel

Datable personnel of Cohors I Aelia Dacorum[14][15]
Date of
Name Military Rank Social Status Nation/tribe Birthplace Notes
c 125 Marcus Clu(dius?) Severus Praefectus Roman knight Italian Cesena Severus, in a funerary stone from Cesena, is described as praefectus of the cohort. Cludius name fits gap in inscription and is attested in votive inscription from Dacia
c. 150 Ti. Claudius Proculus Cornelianus Tribunus Roman knight prob. Numidian Previously commanded Cohors II Bracarum (in Moesia Inferior?); subsequently (153-6) commanded Ala Sulpicia in Germania Inferior
c. 160 Domitius Honoratus Tribunus Roman knight prob. Bithynian Prusias ad Hypium?
205-7 Aurelius Iulianus Tribunus Roman knight British?
219 Marcus Claudius Menander Tribunus Roman knight prob. Greek (from Asia Minor) Ephesus? A Sextus Claudius Menander attested in Ephesus
235-8 Flavius Maximianus Tribunus Roman knight Italian? Praeneste (Latium)? evocatus (veteran) of Cohors I Praetoria (cohort of Praetorian Guard)
237 Aurelius Faustus Tribunus Roman knight Dacian? A veteran with same name attested in Dacia
258-69 Marcius Gallicus Tribunus Roman knight
258-69 Probius Augendus Tribunus Roman knight
270-4 Pomponius Desideratus Tribunus Roman knight Gaul? name attested 6 X in late Gaul
276-82 Aurelius Vinus Tribunus Roman knight
c. 125 Aelius Dida Centurion Roman citizen
c. 126 Decius Saxa Centurion Roman citizen?
293-305 Flavius Martinus Centurion (of I Aelia Dac.?) Roman citizen
Undated personnel of Cohors I Aelia Dacorum[14][15]
Name Military Rank Social Status Nation/tribe Birthplace Notes
Octavius Honoratus Tribunus Roman knight Numidian?
Reginius Iustinus Tribunus Roman knight Gaul or Briton? Acc. to E. Birley, "fabricated" name suggests Celtic origin
Statius Longinus Tribunus Roman knight Italian? Canusium?
Iulius Saturninus Tribunus Roman knight
Terentius Valerianus Tribunus Roman knight Italian? Novara? ?Same as Caius Terentius Valerianus who erected tombstone to son at Novara?
Funisulanus Vettonianus Tribunus Roman knight Italian?
Ammonius Victorinus Tribunus Roman knight
Congaonius Candidus Centurion prob. Gaul or Briton
Dependants of Cohors I Aelia Dacorum personnel
Date of
Name Social status Nation/tribe Birthplace Record
205-7 Aurelius Concordus child (of tribune Aurelius Iulianus), died at 1 year Birdoswald Tombstone, erected by father
uncertain Decibalus
child, died days after birth
child (brother of Decibalus), died at 10 years
uncertain (Dacian name)
uncertain (Roman name)
Birdoswald Tombstone, erected by elder brother

See also


  1. Holder (1980) 18
  2. 1 2 Spaul (2000) 346
  3. Holder (2003)
  4. 1 2 Spaul (1980) 346
  5. Notitia Dignitatum Occidens Title XL
  6. Mattingly (2006) 239
  7. Frere (1987) 133-4
  8. Frere (1987) 133, 135-6
  9. Frere (1987) 147
  10. Frere (1987) 154-5
  11. Spaul (2000) 345
  12. Frere (1987) 166
  13. Spaul (2000) 344
  14. 1 2 Spaul (2000) 344-5
  15. 1 2 Prosop. Mil. Eq. VI pp69-70


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