Roman Legionary Fortresses 27 BC–AD 378

When Augustus reorganized the Roman army following a generation of civil war he decided on 28 legions, which he distributed around the empire. Most were eventually stationed at strategic points for continuing the expansion of Roman power, while maintaining internal security in the frontier provinces. The historian Tacitus, writing around AD 120, briefly records the allocation of legions for the year AD 23, during the reign of Augustus’ successor, Tiberius. Following the Varian disaster of AD 9, when three legions were lost in the Teutoburger Forest, the total had fallen to 25: eight legions were on the Rhine (divided between an upper and a lower district), and four were on the Danube, with another two in the Dalmatian hinterland; three lay in Spain, two were in Africa (where one of the Danubian legions was assisting the resident unit to quell a revolt), two were in Egypt and four were in Syria.We catch another glimpse of the legionary order of battle on a well- known inscription from Rome, listing the legions in geographical order from west to east. Five legions known to have been raised after AD 165 are tacked onto the end, showing that the list was originally compiled before that date – though not long before, as the legion lost in AD 161 (probably IX Hispana) is absent.

From time to time, during the two centuries separating the reigns of Tiberius and Septimius Severus, new legions swelled the numbers under arms. Equally, new units had replaced occasional losses, as individual legions were destroyed in war or, more rarely, disbanded for disgraceful conduct. The historian Cassius Dio, who shared the consulship with the emperor Severus Alexander in AD 229, claimed that only 19 of Augustus’ original legions had survived into the 3rd century AD; the other 14 that existed in Dio’s day had been raised subsequently. Nor did the legionary bases remain static across the centuries. Major manoeuvres, such as the invasion of Britain in AD 43, or the Dacian Wars of AD 101–2 and 105–6, often entailed the re-assignment of legions and the building of new fortresses. However, by the mid-2nd century AD, the situation had settled down and the legionary bases rarely moved thereafter.


Chronology

27 BC Augustus distributes the legions in Gaul (legions XVI Gallica, XVII, XVIII, XIX, XXI Rapax), Spain (legions I, II Augusta, IV Macedonica, V Alaudae, VI Victrix, IX Hispana, X Gemina, XX), Macedonia (legions IIII Scythica, V Macedonica, VII, X Fretensis), Illyricum (probably legions VIII Augusta, XI, XIII Gemina, XIV Gemina, XV Apollinaris), Syria (legions III Gallica, VI Ferrata), Egypt (legions III Cyrenaica, XII Fulminata) and Africa (legion III Augusta) (Total: 27 legions)

25 BC Rome annexes the kingdom of Galatia; the royal troops based there are transferred to Egypt as legion XXII Deiotariana (Total: 28 legions)

14 BC Foundation of the province of Raetia (Switzerland). Legions XVI Gallica and XXI Rapax perhaps occupy a fortress at Augsburg-Oberhausen; legion XIX occupies a fortress at Dangstetten

12–5 BC Roman armies based at Xanten, Cologne and Mainz (Germany) campaign beyond the Rhine; turf-and-timber fortresses are established along the rivers leading east into Germany (e.g., Haltern, Oberaden, Anreppen on the Lippe; Marktbreit on the Main)

AD 4–5 Campaigns beyond the Rhine briefly resumed

AD 6 Legionary battle group assembled at Carnuntum (Austria) for planned invasion of the kingdom of the Marcomanni (modern Czech Republic); thwarted by revolt in the Pannonian hinterland, lasting for three years

AD 9 Destruction of legions XVIII, XVIII, XIX in ‘Varian disaster’ in Germany; widespread troop movements to stop the gap (Total: 25 legions)

AD 30s Double fortress at Cologne replaced by single bases at Neuss (legion XX) and Bonn (legion I); legions V Alaudae and XXI Rapax still at Vetera

AD 39 Emperor Gaius (Caligula) raises legions XV Primigenia and XXII Primigenia for projected German campaign (Total: 27 legions)

AD 41–54 Reign of Claudius. General rebuilding in stone at many legionary fortresses

AD 43 Invasion of Britain (probably with the four legions later found in garrison); major troop movements elsewhere

AD 46 Annexation of Thrace accompanied by construction of fortress at Novae (Bulgaria)

AD 66 Emperor Nero raises legion I Italica for the projected Caspian campaign (Total: 28)

AD 68 Nero raises legion I Adiutrix for the civil war; the pretender Galba raises legion VII Hispana (or Galbiana) in Spain (Total: 30)

AD 69 Emperor Vespasian raises legion II Adiutrix (Total: 31)

AD 70 Legions XV Primigenia and V Alaudae (?) destroyed in civil war; I Germanica disbanded in disgrace; IV Macedonica and XVI Gallica reconstituted as IV Flavia felix and XVI Flavia firma; VII Hispana (or Galbiana) becomes VII Gemina (Total: 28)
Double camp at Vetera replaced by single fortress (Vetera II)

AD 83 Emperor Domitian raises legion I Minervia for campaign against the Chatti in Germany (Total: 29)

AD 84/7 Fortress at Inchtuthil (Scotland) founded by legion II Adiutrix (?) and rapidly abandoned

AD 89 Domitian officially bans brigading legions together; double fortress at Mainz replaced by single camp

AD 92 Legion XXI Rapax (?) destroyed in fighting across the Danube (Total: 28)

c. AD 105 Emperor Trajan raises legions II Traiana and XXX Ulpia for Second Dacian War (Total: 30)

AD 106 Annexation of Arabia and construction of fortress at Bostra (Syria) by legion III Cyrenaica

AD 117 Trajan transfers a second legion to Judaea, probably II Traiana, based at Caparcotna (Israel)

AD 122 Legion XXII Deiotariana (?) destroyed in rioting in Alexandria (Total: 29)

AD 161 Legion IX Hispana (?) destroyed in fighting in Armenia (Total: 28)

AD 165 Emperor Marcus Aurelius raises legions II Italica and III Italica for Marcomannic War and invasion of Suebian territory (Total: 30)

AD 179 Fortress of Castra Regina (Germany) founded by legion III Italica

AD 197 Emperor Septimius Severus raises legions I Parthica, II Parthica and III Parthica for Parthian expedition; construction of fortress at Albanum (Italy) (Total: 33)

c. AD 200 Fortress at Lauriacum (Austria) founded by legion II Italica