The size of the auxiliary cohorts is a matter of even greater difficulty. Hyginus states, and there seems no reason to doubt his statement, that a cohors miliaria was divided into ten centuries, a cohors quingenaria into six.[52] Archaeological evidence supports this statement and suggests further that the centuries were in each case of the same size, since the centurial barracks in the fort at Housesteads, in Northumberland, which was occupied by a cohors miliaria, offer almost precisely the same accommodation as those in the Scottish fort at Newstead, which are clearly designed to accommodate two cohortes quingenariae. The question to be decided is whether these centuries contained 80 or 100 men each. In either case, one of the titles must be a misnomer, since six centuries of 100 would make a cohors quingenaria consist of 600 men, while ten centuries of 80 would only give 800 men for a cohors miliaria. On the whole, although Hyginus suggests the higher figure, the lower is probably to be preferred. Certainly the Coptos inscription cited above, which is probably the most valuable evidence which we possess, clearly indicates centuries of 80. The most important evidence on the other side is that of Josephus, who describes some cohorts which belonged to the Syrian army in 67 A.D. as containing ἀνὰ χιλίους πεζούς.[53] His succeeding statement, however, that other cohorts, by which cohortes equitatae quingenariae are apparently meant, contained 600 infantry and 120 cavalry, suggests that he may be basing his reckoning simply on the number of centuries. Few would defend his calculation in the second instance, and he may be equally wrong in the first. On the whole, therefore, it seems safer to assume establishments of 480 and 800 men for cohortes quingenariae and miliariae respectively, although it remains, of course, possible that the size of the cohorts was altered between the Jewish war of 66-70 and the period of the erection of those frontier forts upon which we have been relying for our evidence.
The last question to be settled in this connexion is that of the cohortes equitatae, in which a proportion of the men were mounted, which form a peculiar and interesting feature of the imperial army. Corps in which infantry and cavalry fought together had of course always been common,[54] but the idea was probably revived by the Romans from observing the practice of the German tribes, from whom Julius obtained a contingent accustomed to fight in this manner.[55] It is certainly significant that one of the earliest of these regiments known to us from inscriptions is a cohors Ubiorum.[56] There is, however, no later evidence for the employment of these tactics, and the continued use of cohortes equitatae is due rather to the necessity of having detachments of mounted men at as many frontier stations as possible. The equites cohortales should be reckoned rather as mounted infantry than cavalry, since we learn from a fragment of Hadrian’s address to the army in Africa that they were worse mounted than the equites alares, and less skilled in cavalry manœuvres.[57] As regards the strength of these regiments and the proportion of mounted to unmounted men, Hyginus states that the cohors miliaria equitata contained 760 infantry and 240 cavalry, while the cohors quingenaria contained six centuries, and in other respects, ‘in dimidio eandem rationem continet’—that is to say, it apparently had 380 infantry and 120 cavalry.[58] The figures for the mounted men are probably correct, and, since we learn from an inscription that there were four decurions to a cohors quingenaria, we may presume that the turmae were 30 strong.[59] This agrees very well with the Egyptian vexillation cited above, which included 61 equites cohortales—that is to say, 2 turmae. On the other hand, there is considerable reason for supposing that the figures for the infantry are schematic and incorrect. It is sufficient here to remark that centuries of 76 could not be divided into contubernia of either 8 or 10, and that the 380 men of Hyginus’s cohors quingenaria could not even be divided evenly among six centuries. The question cannot be settled with certainty until forts occupied by regiments of this class have been planned, but it seems probable that while the number of the centuries remained unaltered the complement of each was reduced from 80 to 60, or possibly to 64, if it was thought desirable to retain the division into contubernia of 8.[60]
Having endeavoured to determine the theoretical establishment of the auxiliary regiments, it remains to discover how far this corresponded to the actual strength at which they were maintained, and here our evidence is scanty, and likely to remain so. Fortunately, the discovery in Egypt of some of the official papers of the Cohors I Augusta Praetoria Lusitanorum has thrown some light on the question. On January 1, 156, this regiment had on its books 6 centurions, 3 decurions, 114 mounted infantry, 19 camel-riders (dromedarii), and 363 infantry, making, with the praefectus, a total of 506 men. Between January and May, 18 recruits were enrolled, 15 infantry, an eques, a dromedarius, and a decurion.[61] These figures agree fairly well with the arrangement suggested above, although the dromedarii are an additional complication, and the regiment appears even to have exceeded its ‘paper-strength’. This, however, may be easily accounted for if we imagine that a number of men had served their term and were about to be discharged. Unfortunately, this document remains isolated, and further evidence is not likely to be forthcoming.
Conditions of service. Questions concerning the method of enlistment for the auxiliary regiments are reserved, on account of their connexion with the broader issues raised by the whole recruiting system, for discussion in a later section. For the present it will be sufficient to discuss the conditions of service in this branch of the army, as they are laid down in the so-called diplomata militaria.[62] These documents, of which we possess some 70 or 80 examples dealing with the auxilia, are small bronze tablets, issued originally to individual soldiers, recording the privileges granted to them either after their discharge or after they had completed a term of 25 years. The reason for this variation seems to be that while the praemia militiae were always conferred after the regulation number of years had been served, it was often the practice to retain the men with the colours for some years longer before finally discharging them. This practice, which we hear of in the early empire as a standing grievance of the legionaries,[63] seems to have prevailed also among the auxilia during the first century.[64] After 107, however, we have no instances of the praemia unpreceded by discharge, a change which is probably due to the perfection of organization, and can be traced also in the legions.
Previous to the reign of Antoninus Pius, the privileges granted to the recipient of a diploma include citizenship for himself, the full legalization of any matrimonial union into which he has entered or shall enter in the future (conubium), and civic rights for his wife, children, and descendants. If he already possessed a family, the names of his wife and children follow his own on the diploma, and the frequency of this occurrence shows the extent to which the military authorities permitted the soldiers to form family ties while on active service.[65] The significance of this fact and its effect on the character of the army will be discussed in a later section.
At the beginning of the reign of Antoninus Pius, a change takes place in that part of the formula which concerns the grant of citizenship. In place of the words ipsis liberis posterisque eorum civitatem dedit et conubium cum uxoribus, &c., we read in all the later examples, civitatem Romanam, qui eorum non haberent, dedit et conubium cum uxoribus, &c.[66] The first inference to be drawn from this alteration is that there now existed a numerous group of auxiliary soldiers who possessed the civitas before their discharge, and we are probably justified in the further inference that many actually possessed it when they were enrolled. It has been noted, for example, that on a document dating from the reign of Trajan, six recruits accepted for the Cohors III Ituraeorum all have the tria nomina.[67] In this change, then, we have a clear instance of the extent to which the franchise was now diffused throughout the Empire.
The omission of the phrase liberis posterisque eorum, on the other hand, suggests the opposite tendency. It cannot, of course, mean that children born after their father’s discharge would not be cives, for their status would be secured by the grant of conubium, but it seems clear that those born before it no longer acquired the citizenship with him. This is supported not only by the absence of all mention of children on the later diplomata,[68] but by the phraseology of an Egyptian document dealing with an ἐπίκρισις of the year 148 which distinguishes two classes of veterans, ἔνειοι μὲν ἐπιτυχόντες σὺν τέκνοις καὶ ἐγγόνοις, ἕτεροι μόνοι τῆς Ῥωμαίων ποτειτείας (sic) καὶ ἐπιγαμίας πρὸς γυναῖκας ἃς τότε εἶχον, ὅτε τούτοις ἡ πολιτεία ἐδόθη,[69] &c. Clearly we have here a translation of both types of formula, and the translator gave to the second the same meaning as that suggested above. Clearly, too, the change was considered an important one since the veterans discharged before and after it are thus divided into two groups. In view of the prevailing policy of the imperial government with respect to the extension of the civitas this step has a curiously retrograde appearance, and it is difficult to see the motives which suggested it. Possibly it was merely desired to get rid of an anomalous situation by which the auxiliaries had previously occupied a more privileged position than the Household Troops.[70] In any case, even after this restriction, there can be little doubt that the grant of the civitas with the improvement in civil status which it brought to the recipient, and the increased possibilities which it offered to his children, must have done much to popularize the service. We have seen that the idea of such a reward did not originate with the Empire, but it was probably not until the reorganization of the army by Augustus that it was regularly conferred and the years of service required to earn it definitely fixed.[71]
We do not know whether at the time of their discharge the auxiliaries also received, like the legionaries, a grant of money or land in lieu of a pension. It seems certain that their status excluded them from a share in the donativa, which the emperors distributed among the troops at their accession, and on other special occasions, and that they could only receive the dona militaria after a special preliminary grant of the civitas.[72] That such grants were made, even to whole regiments at a time, is shown by the number of cohorts which commemorate the receipt of this honour by employing the title civium Romanorum.
On the still more important matter of the ordinary pay of the auxiliary regiments an almost equal uncertainty prevails. Our only two pieces of evidence on the subject, a passage in Tacitus and a phrase in Hadrian’s address to the garrison of Africa,[73] tell us nothing more than that the equites cohortales were paid on a higher scale than the infantry, but received in their turn less than the equites alares, a preference in favour of the mounted men, which is not so great as appears at first sight, since it is clear that they were responsible for the upkeep of their own horses. The chief defect of these passages is that they do not mention the amount of the pay in any of the three cases. Our only basis for calculation is the fact that a legionary considered it promotion to be made duplicarius alae; hence the pay of an ordinary cavalryman must have been more than half that of a legionary. On a priori considerations it can hardly have been less, if, as Hadrian’s speech suggests, he paid for his own arms and mount, and if he also, like the legionaries, had the cost of his rations deducted from his pay. On the whole, however, it seems best to defer speculation until further evidence is forthcoming.[74]
Internal organization. As is only natural in the case of a professional army with so long a term of service, the internal organization of the auxiliary regiments reveals a far more complicated system of grades and promotions than anything which the ancient world had yet known. The epigraphical evidence is abundant, and the efforts of modern scholars, particularly von Domaszewski in his monumental treatise, Die Rangordnung des römischen Heeres, have done much to make the main lines of the system clear. Difficulties in detail still remain, but we may hope for their ultimate solution.