A catalogue of the Roman legions

In the days of the Republic, a legion was recruited by an army commander after he had been given a task by the Senate, whether to conquer a new province or hold an old one. When the task was completed, the legion - a collection of volunteers, all who should be Roman citizens - should have disbanded.

During the last of the Civil Wars, the three Triumvirs each raised their own army, as did the pirate chief Sextus Pompeius. Augustus Caesar persuaded Lepidus's 14 legions (and the 8 that joined Lepidus after Pompeius had abandoned them) to desert to him, after which he engaged and defeated Marcus Antonius. The battle of Actium, in 31 B.C., left Augustus the undisputed master of Rome and her empire, but also left him with more than 50 legions, far too many for the peaceful era that was to come.

Augustus completely reorganised the Roman forces. Instead of temporary volunteers, there was to be a standing army. By disbanding some and merging others, he ended up with a new force of 28 legions. Most of these were to last for more than two centuries, more than half for four, and one - the V Macedonia - was still to be found in the sixth century A.D.

Augustus's original 28 legions were as follows:

The 6 legions with duplicate numbers show that at least some numbers were retained from the original armies - all three 3rd legions were retained. Equally, it is clear that some numbers must have been allocated anew, otherwise the neat sequence to 22 would not have happened.

The legions' names have varying origins. The legions with duplicated numbers presumably bear names indicating which army they came from. The legions Augusta were presumably from his own army, and perhaps distinguished themselves in some way at some time, while the V Alaudae were recruited from Gallic provincials by Julius Caesar. The three legions Gemina were amalgamations of two or more of the pre-Actium legions. Suetonius mentions that Augustus once disbanded a Tenth legion, but perhaps they were actually amalgamated. It is clear that some of the legions were unnamed at their creation; the XVII, XVIII, and XIX never gained a name before they were lost in the Tuetoburg Wald in 9 A.D., and the VII and XI gained their names ("the Loyal Claudians") after they refused to rebel in 42 A.D., though the VII had a previous name. But some names are totally obscure.

The Julio-Claudian Emperors

The loss of three legions near the end of Augustus' reign brought the army down to 25 legions. Only two of the subsequent Julio-Claudian emperors were to do anything about this, but by the end of Nero's reign in 68 A.D., the strength was back to 28 legions again:

Claudius 43 A.D. Primigenia Claudius 43 A.D. Primigenia Nero 67 A.D. Italica

There is some dispute about whether Caligula or Claudius raised the first two, but the latter is more likely, as 4 legions were about to be taken to the invasion of Britain (II Augusta, IX Hispania, XIV Gemina, and XX Valeria Victrix), and some replacements would be necessary.

The Flavian reforms

In 68 A.D. the Senate declared Nero a public enemy, and appointed Galba to the Imperium, probably the last significant political action they were ever to take. Galba took his own legion from Spain, raised a second - the VII Galbiana - and marched on Rome. Various other commanders opposed him, and the resulting wars produced four emperors within the same year - 69 A.D. - with the eventual triumph of Vespasian, founder of the Flavian dynasty.

After such a great conflict, it was clear that some legions could no longer be trusted, and others needed to be raised to replace them. The Flavian reforms of 70 A.D. were probably the greatest changes to be made to the Roman army since the Augustan reorganisation.

One legion - the XV Primigenia - presumably was too closely identified with one of the losing emperors, and was disbanded. Two new legions were formed:

Adiutrix Adiutrix

and two others

Germanica Galbiana

were merged to form the new VII Gemina.

Finally, two other legions, supporters of Vespasian from the start, gained new names.

was became Macedonia Flavia Felix Gallica Flavia Firma

The middle empire

Over the next 140 years, 4 legions were to be lost in wars, and 8 raised to replace them or otherwise strengthen the army for specific campaigns.

A.D. by raised 83 Domitian Minervia lost 87 [Domitian] Alaudae lost 92 [Domitian] Rapax raised 102 Trajan Trajana raised 102 Trajan Ulpia Victrix lost in Judea 132 [Hadrian] Hispania lost 135 [Hadrian] Deiotariana raised 165 Marcus Aurelius Pia Italica raised 165 Marcus Aurelius Concors Italica raised 197 Septimus Severus Parthica raised 197 Septimus Severus Parthica raised 197 Septimus Severus Parthica

Including the three raised for the Parthian wars, Rome had 33 legions defending its territories. In 215 A.D., these were occupying postings around the various provinces as follows (the date of posting is shown where known).

Adiutrix Lower Pannonia Italica Lower Moesia Minervia Lower Germany Parthica Mesopotamia Adiutrix Lower Pannonia 90 Augusta Upper Britain (Caerleon) 43 Parthica Italy 197 Pia Italica Noricum 176 Trajana Egypt Augusta Numidia by Augustus Concors Italica Raetia Cyrenaica Arabia Gallicia Syria Phoenice Parthica Mesopotamia Flavia Felix Upper Moesia Scythica Syria Coele Macedonia Upper Dacia Ferrata Syria Palaestina Victrix Lower Britain (York) 122 Claudia Pia Fidelis Upper Moesia Gemina Nearer Spain Augusta Upper Germany Fretensis Syria Palaestina Gemina Upper Pannonia before 130 Claudia Pia Fidelis Lower Moesia Fulminata Cappadocia Gemina Upper Dacia Gemina Martia Victrix Upper Pannonia Apollinaris Cappadocia 114 Flavia Firma Syria Coele Valeria Victrix Upper Britain (Chester) 43 Primigenia Upper Germany before 130 Ulpia Victrix Lower Germany

Note that "Upper" and "Lower" were political designations, so Upper Britain, for example, was the southern half of the island and Lower Britain the northern half.

The Notitia Dignitatem

The situation in 215 was probably the heyday of the classical legion. Over the next 200 years, many more were to be lost in battle, or just to be disbanded or fade away. The tide of warfare was turning away from the classical infantry battle, and towards cavalry warfare between bands of mercenaries fighting for Rome - so long as she paid - on the one hand, and rebels and barbarians on the other. The traditional legions became the garrison troops, settled in a province, with retired legionaries marrying local women and their sons and grandsons enlisting in their turn.

In such a situation, it would be rare for a legion to move posting, and indeed the record shows none doing so. In 395 A.D., the Notitia Dignitatem (a record of all the appointments in the empire) shows only 24 legions remaining, all unmoved for 180 years.

Adiutrix Lower Pannonia Italica Lower Moesia Parthica Mesopotamia Adiutrix Lower Pannonia Parthica Italy Pia Italica Noricum Trajana Egypt Concors Italica Raetia Cyrenaica Arabia Gallicia Syria Phoenice Flavia Felix Upper Moesia Scythica Syria Coele Macedonia Upper Dacia Victrix Lower Britain (withdrawn in 406) Claudia Pia Fidelis Upper Moesia Gemina Nearer Spain Fretensis Syria Palaestina Gemina Upper Pannonia Claudia Pia Fidelis Lower Moesia Fulminata Cappadocia Gemina Upper Dacia Gemina Martia Victrix Upper Pannonia Apollinaris Cappadocia Flavia Firma Syria Coele

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