Total number of the auxilia. This section should naturally conclude with some statement of the total number of auxilia in the imperial service. Unfortunately, no clear and direct evidence can be obtained on this point either from literary or epigraphical sources. Tacitus, in his survey of the military resources of the Empire in the reign of Tiberius, after enumerating the legions in detail, contents himself with a vague sentence suggesting that the auxiliaries were as numerous as the legionaries and Household Troops.[149] This phrase is perhaps accurate enough for the period to which he is referring, but it is obviously not meant to be precise, and must certainly not be taken to express any principle habitually followed in the composition of the imperial army. If we endeavour to check the statement from other sources we have the remark of Velleius that in 6, at the time of the great Pannonian revolt, the ten legions concentrated under Tiberius’s command were accompanied by 70 cohorts and 14 alae.[150] If we allow for a few regiments being miliariae, this would represent a little over 50,000 men, a number about equivalent to that of the legionaries. If we may assume a similar ratio in other provinces, the total for the auxilia at this period would amount to 150,000 men.[151] It must be remembered, however, that at this date and throughout the whole pre-Flavian period the government relied upon the troops of the client kingdoms and levies of border militia to supplement the imperial troops. With the gradual elimination of these secondary forces, which has already been described, the number of regular units was proportionately increased. More than twenty regiments were raised in the old kingdom of Thrace after its annexation in 46, and five alae and nineteen cohorts are found in 69 garrisoning the two provinces which had been formed from the kingdom of Mauretania.[152] We need not, then, be surprised if the figures supplied by Tacitus and Josephus show that so early as 69 the number of the auxiliaries considerably exceeds the figure suggested for the end of the reign of Augustus. According to Josephus, Vespasian entered Judaea in 67 with at least 20,000 auxiliaries, which probably represents two-thirds of the total number available in the Eastern provinces.[153] In the Danubian provinces in 69 there were, according to Tacitus, sixteen alae.[154] On the basis of the information given in the diplomata, we can safely reckon that there would be at least three cohorts to every ala, and that one regiment in four would be miliaria. Some 40,000 auxiliaries, therefore, must have been stationed in the Danubian provinces at this period. In the same year Vitellius entered Rome with twelve alae and thirty-four cohorts, that is to say some 30,000 men, which represented probably two-thirds of the auxilia in the Rhine armies and Raetia.[155] The garrison of the two Mauretanias, to which allusion has already been made, would amount to about 15,000 men. We thus arrive at the following totals for the auxilia at this period:
| The Eastern provinces | 30,000 | men |
| The Danubian provinces | 40,000 | „ |
| Germany and Raetia | 45,000 | „ |
| The two Mauretanias | 15,000 | „ |
| 130,000 | „ |
To this at least another 50,000 men must be added for the auxilia of Britain, Spain, Africa, Noricum, and the small garrisons of the inland provinces, making a grand total of 180,000 men. The next forty years saw the figure mount even higher. The remaining client kingdoms in the East, which were still strong enough to furnish 15,000 men for the Jewish war in 67, were annexed, and the appearance of several new units with the titles Flavia or Ulpia shows that more than this number of regular auxilia was raised in their place.[156] Even Hadrian seems to have made a few additions to the list, since his foreign policy, though essentially pacific, was based upon a system of frontier defence to which the auxilia were more than ever essential.[157] In Appendix I, where the evidence as to the strength and distribution of the auxilia in the second century is discussed in detail, it is suggested that by the middle of the second century the force may have amounted to some 220,000 men, and that even this figure was probably exceeded sixty years later.
FOOTNOTES:
[34] De Bell. Afr. 78.
[35] Cicero, De Off. ii. 13. 45.
[36] In a note to the French translation of Mommsen and Marquardt (xi. 105) von Domaszewski declares decidedly against the possibility that the equites sociorum were organized in alae. Writing in Pauly-Wissowa (s.v. Auxilia), he seems to consider that the auxiliary cavalry had adopted the formation before the close of the Republic, although the passages to which he refers, those from Cicero and the author of the Bell. Afr. which are given above, seem at least to be susceptible of a different interpretation.
[37] For praefecti equitum cf. Caesar, Bell. Gall. iii. 26; iv. 11. They are not to be thought of as merely commanding turmae, since we have a decurion mentioned in Bell. Gall. i. 23.