The numbering of the legions and their titles

The legions were originally named according to the order in which they were raised. Thus in the early part of the second Punic war, we hear of the fourth legion (to tetarton stratopedon), being hard pressed by the Boii (Polyb. iii.40); the tenth legion plays a conspicuous part in the history of Caesar as his favourite corps (Dion Cass. xxxviii.17), and the cabinets of numismatologists present us with an assemblage of denarii struck by M. Antonius in honour of the legions which he commanded, exhibiting a regular series of numbers from 1 up to 30, with only four blanks (25, 27, 28, 29). As the legions became permanent, the same numbers remained attached to the same corps, which were moreover distinguished by various epithets of which we have early examples in the Legio Martia (Cic. Philip. v.2; Vell. Pat. ii.61; Dion Cass. xlv.13; Appian, B. C. iv.115), and the Legio Quinta Alauda [ ALAUDA ]. Dion Cassius, who flourished under Alexander Severus, tells us (lv.23) that the military establishment of Augustus consisted of twenty-three or twenty-five legions (we know from Tac. Ann. iv.5, that twenty-five was the real number), of which nineteen still existed when he wrote, the rest having been destroyed, or incorporated by Augustus or his successors in other legions. He gives the names of nineteen, and the localities where they were stationed in his own day, adding the designations of those which had been raised by subsequent emperors. This list has been considerably enlarged from inscriptions and other authorities, which supply also several additional titles. We give the catalogue as it stands in the pages of the historian, and refer those who desire more complete information to the collections of Roman inscriptions by Gruter and Orelli, to the fifth book of the Comment. Reip. Rom. of Wolfgang Lazius, fol. Francf. 1598, and to Eckhel, Doctrina Numm. Vet. vol. vi p50, vol. viii p488. In the following table an asterisk is subjoined to the nineteen legions of Augustus, to the remainder the name of the prince by whom they were first levied; the epithets included within brackets are not given by Dion, but have been derived from various sources:— List of the Legions in the Reign of Alexander Severus.

On this we may remark:—

1. That several legions bore the same number: thus there were four Firsts, five Seconds, and five Thirds.

2. The titles were derived from various circumstances; some indicated the deity under whose patronage the legions were placed, such as Minervia and Apollinaris; some the country in which they had been levied or recruited, as Italica, Macedonica, Gallica; or the scene of their most brilliant achievement, as Parthica, Scythica; some the emperor under whom they had served or by whom they had been created, as Augusta, Flavia, Ulpia; some a special service, as Claudiana Pia Felix, applied to the 7th and 11th, which had remained true to their allegiance during the rebellion of Camillus, prefect of Dalmatia, in the reign of Claudius (Dion Cass. lx.15); some, the fact that another legion had been incorporated with them; at least, this is the explanation given by Dion Cassius of the epithet Gemina (Diduma), and there seems little doubt that he is correct (see Eckhel, vol. iv p472).

3. The same legions appear in certain cases to have been quartered in the same districts for centuries. Thus the Secunda Augusta, the Sexta Victrix, and the Vicesima Victrix, which were stationed in Britain when Dion drew up his statement, were there in the age of the Antonines, as we learn from Ptolemy (ii.31), and the first of them as early as the reign of Claudius (Tac. Hist. iii. 22, 24).

4. The six legions of Augustus which had disappeared when Dion wrote, were probably the following, whose existence in the early years of the empire can be demonstrated: Prima Germanica; Quarta Macedonica; Quinta Alauda; Nona Hispana; Decima Sexta Gallica; Vigesima Prima Rapax; besides these, it would seem that there was a second fifteenth and a twenty-second, both named Primigenia, and one of these ought, perhaps, to be substituted for the second twentieth in the above table, since the words of Dion with regard to the latter are very obscure and apparently corrupt.

5. We find notices also of a Prima Macriana Liberatrix raised in Africa, after the death of Nero, by Clodius Macer; of a Decima Sexta Flavia Firma raised by Vespasian; and of a Vigesima Secunda Deiotariana, apparently originally a foreign corps, raised by Deiotarus, which, eventually, like the Alauda of Caesar, was admitted to the name and privileges of a Roman legion.

6. It will be seen that the numbers XVII, XVIII, XIX are altogether wanting in the above lists. We know that the XVIII and XIX were two of the legions commanded by Varus, and hence it is probable that the XVII was the third in that ill-fated host.

7. The total number of legions under Augustus was twenty-five, under Alexander Severus thirty-two, but during the civil wars the number was far greater. Thus, when the second triumvirate was formed the forces of the confederates were calculated at forty-three legions, which, after the battle at Philippi, had dwindled down to 28 (Appian, B. C. v.6); but a few years afterwards, when war between Octavianus and M. Antonius was imminent, the former alone had upwards of forty legions, and his adversaries nearly the same (Appian, B. C. v.53). In order that we may be able to form some idea of the magnitude of these and other armies, we must next consider the number of soldiers in a legion.

   William Smith, A Dictionary of Greek and Roman Antiquities, John Murray, London, 1875. pp489-511.