Military history

APPENDIX D

THE NAMING AND NUMBERING SYSTEM OF THE ROMAN LEGIONS

Until 31 B.C., legions had numbers or names, but apparently not both. In 84 B.C., Pompey the Great began the habit of always numbering his new legions, a habit subsequently adopted by Julius Caesar. In his major reform of the Roman army, begun in 31 B.C., Augustus reduced the legions to twenty-eight in all, giving each a number between 1 and 28. It was an admirably practical system. For less practical, more nostalgic reasons, he also allowed several existing legions to combine their old names with their new numbers. For the next hundred years, it was sufficient to know a legion’s number to be able to identify it. But in the civil war that followed the demise of Nero, in A.D. 68–69, things changed dramatically.

Considerable confusion has been caused over the years by the fact that from about A.D. 67 the numbers of the legions of Rome began to be duplicated so that by the end of the war of succession—late A.D. 69—there were four 1st Legions, three 3rd Legions, and two of each of the 2nd, 4th, 5th, 6th, 7th, 10th, and 15th Legions.

New legions continued to be added and others abolished as the years passed. By A.D. 233 there had been seven different 1st Legions, and there were still four 2nd Legions. To identify a Roman legion after A.D. 68, it’s necessary to also look at its title—was it the 6th Victrix or the 6th Ferrata, for example, the 10th or the 10th Gemina?—two quite different legions.

It had all begun very methodically. The four original legions annually levied in Rome in republican times were numbered 1 through 4. Other legions supplied to Rome by the Italian allies carried the names of their tribes rather than numbers—the Martia Legion, famous in its day, would have been supplied by the Marsi tribe southeast of Rome, for example, the tribe and the legion being named for the war god Mars.

The numbering system that developed in the first century B.C. carried through the subsequent history of imperial Rome. It was begun by Pompey the Great when he personally raised and financed several legions in the Picenum region of eastern Italy in 84 B.C., naming two of them the 1st and 2nd Legions. Pompey subsequently raised the 3rd, 4th, 5th, 6th, 7th, 8th, and 9th Legions. When Julius Caesar arrived in Farther Spain in 61 B.C. to take up his appointment as governor of the province, he raised a new legion locally and, following Pompey’s system, he called it the 10th. Over the next few years, Caesar raised six more legions for his campaigns in Gaul and Britain—the 11th through the 16th. Shortly after, the triumvir Crassus raised a number of legions to take to war against the Parthians, managing to have himself killed and most of his legions wiped out at the Battle of Carrhae. It appears that these legions may have had names rather than numbers.

A few years later, Cicero took two new Italian-raised legions to Cilicia when he became governor there in 51 B.C. They, too, may have had names, but none that is recorded. When Pompey the Great took them over in 49 B.C., these two units were simply known as the Cilician Legions, because they were based in Cilicia. Pompey’s father-in-law, Metellus Scipio, commanded two Italian-raised legions based in Syria at this time, survivors of Carrhae, and in the same way they were known as the Syrian Legions.

Between 49 and 48 B.C. Caesar created nineteen new legions for use in the civil war against Pompey, numbering them 17 through 35. After he defeated Pompey at the Battle of Pharsalus, he took two cohorts of one of Pompey’s surrendered legions, the 6th, into his army, and had his officers seek volunteers from Pompey’s other legions, giving the resulting two new legions created from POWs the numbers 36 and 37.

By 31 B.C., after Caesar’s assassination on the Ides of March, 44 B.C., and the new civil wars that followed, at least fifty-nine legions were in the field—some accounts suggest as many as sixty-two—most with their Pompeian and Caesarean numbers.

Once Octavian had defeated Antony and Cleopatra in 31 B.C. he inherited all fifty-nine legions, most of them well understrength after years of fighting. Augustus reduced these to twenty-eight, abolishing some of the old legions, or sometimes combining two legions into one.

When Pompey the Great combined men from two so-called Cilician legions in 49 B.C., he named the resulting single legion the Gemina, meaning “twin.” Several legions folded into each other by Augustus in 31–30 B.C. also took the name Gemina. Two Augustan Gemina legions were still in existence in A.D. 233— the 13th Gemina and the 14th Gemina Martia Victrix. The Gemina tradition was to be continued by later emperors—a legion created in A.D. 68, the second 10th, became the 10th Gemina two years later via combination with another. In the same way, Galba’s 7th, also founded in A.D. 68, was likewise combined with another legion in A.D. 70, to become the 7th Gemina.

Four legions created in the changes of 31–30 B.C.—the 14th Gemina, the 20th Valeria, the 21st Rapax, and the 22nd Deiotariana—bore titles as well numbers from that time. This was because Augustus gave the old Martia Legion, one of the most celebrated of its day, the number 20 when he discharged the Italian legionaries of the 20th in 31 B.C. and allowed the legion to keep its famous old name in addition to its new number. Likewise, the equally famous Valeria Legion, raised by Pompey, took the number 20. That legion’s second title, Victrix, was added a few years later. And when the Galatian legion called the Deiotariana was given the number 22, it also retained its title, until the reign of Claudius, in deference to the memory of King Deiotarus of Galatia, the legion’s founder. The 21st Rapax also seems to have taken a pre-30 B.C. title with it.

Early in his reign, Augustus bestowed titles on legions as a reward, or to celebrate their land of origin, no doubt an honor and a reward to the province concerned. Later emperors granted titles to legions for varying reasons. Some, like the 15th, were never granted a title, despite having played important roles in major campaigns. And the 12th Legion wasn’t granted its title of Fulminata until A.D. 174.

There was one blip in the Augustan numbering system. After three legions were wiped out in Germany in A.D. 9, Augustus retired their numbers. One, we know, was the 19th. There are good reasons to believe that the others were the 25th and the 26th. Augustus never replaced the annihilated legions and never used their numbers again, a step respected by every subsequent Roman emperor, none of whom used the numbers retired by Augustus, even though many of them raised new legions. For the next twenty-five years the Roman army consisted of twenty-five legions, still bearing the numbers 1 through 28 but minus 19, 25, and 26.

Nero raised a new legion in Italy, the 1st Italica, in A.D. 66–67, setting the scene for the overuse of the number 1 in coming years. In A.D. 68, Nero created the 1st Legion of the Fleet as one of his last, desperate acts as emperor. That same year, Servius Galba, Governor of Farther Spain, built an army to challenge Nero. Galba levied new legions in the traditional recruiting grounds of established Spanish legions. Within a few months he had created second the 4th, 5th, 6th, 7th, and 10th Legions in Spain.

There was a logic of a kind to his system, but the numbering of some subsequent new legions applied a logic all their own. For example, in A.D. 68, the city of Vienne in southern France created a 1st Adiutrix Legion to “support” the 1st Italica Legion, which was stationed nearby, to prove the town’s loyalty and to discourage the 1st Italica from sacking their city. When the 1st Adiutrix subsequently fought on the losing side, the people of Vienne hurriedly raised a 2nd Adiutrix to prove their loyalty to the new emperor—the original 2nd, the Augusta, was also raised in their province, hence the duplication of its number, as a “supporter” to the original 2nd.

The 3rd Gallica Legion takes its name and number from the fact that it was the third new legion raised in Gaul at that time, after the 1st Adiutrix and the 2nd Adiutrix. There are in fact explanations for the numbering of all but one of the many legions created in 68–69. The exception is the 3rd Cyrenaica. There is no obvious reason for the new legion raised in Cyrenaica to be yet another 3rd Legion. It is possible that Syrian veterans of the 3rd Augusta Legion discharged eight years before had settled in Cyrenaica and formed the basis of the new legion hurriedly recruited in A.D. 68, but there is no proof of this.

Vespasian consolidated the army once he came to power at the end of A.D. 69, abolishing some of these new legions created during the civil war and merging others, in the first major reorganization of the Roman army since the time of Augustus. Occasionally Vespasian’s successors raised new legions, and almost always they chose to keep the numbers they allocated these new units within the bottom end of the existing number range, so that we find several new legions taking the numerals 1, 2, or 3 over the next 150 years.

The reasoning behind the numbering of these later legions varies. Domitian raised one legion and called it his 1st—the 1st Minervia, named after his patron deity. Severus Alexander founded the 1st, 2nd, and 3rd Parthicae Legions for operations against the Parthians. Marcus Aurelius raised two new legions in Italy, so they naturally became the 2nd and 3rd Italica, since Nero had raised the 1st Italica.

Yet Trajan complicated matters with the numbers he gave the four new legions he raised in A.D. 100 for his campaigns in Dacia. Only two of the these lasted into the third century—the 2nd Traiana and the 30th Ulpia, both named after Trajan. Their numeration means there were also at one time a 1st Traiana and a 29th Ulpia Legion.

A full listing of the legions of the late first century B.C. to the early second century A.D. is given in Appendix A.

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