The Auxilia of the Roman Imperial Army

by George Leonard Cheesman

It has already been noted that the frontier system adopted in the second century had obvious defects.

It can easily be seen that if the strongly guarded frontier line were broken through at any point the internal provinces were exposed to the greatest danger. In themselves they possessed no means of making a stand against an invader. Their garrisons were small, cut down in fact to the minimum quantity required for police duty, and the provincial militia, which we hear of during the first century, seems no longer to have existed except in Mauretania. In fact, now that the army was recruited almost entirely in the frontier provinces, the profession of arms must have been more unfamiliar to the inhabitants of Western Europe and Asia Minor than it has ever been since, and many a citizen of the prosperous little towns of Gaul, Africa, or the Hellenized districts of the East can never have set eyes on the imperial uniform. The situation was clearly a dangerous one, and the lesson of the Marcomannian War must have made it clear that this system could only continue if the frontier troops were supported by a strong and mobile striking force, ready to move at a moment’s notice to any threatened point.

In the second century the only available regiments not occupied in frontier defence or police duty consisted of the Household Troops at Rome, i.e. the ten Praetorian cohorts and the Equites Singulares. The Guards were in fact employed by Domitian, Trajan, and Marcus on the Danube frontier, but their numbers were small, their duties were not calculated to increase their military efficiency, and they were rightly looked down upon by the trained veterans of the frontiers.[414] The gravity of the situation was grasped by Septimius Severus, who took advantage of the discredit in which the Praetorians were involved by their support of Didius Julianus to disband the old cohorts, which had been recruited in Italy and the ‘civilized’ provinces of Noricum, Macedonia, and Spain, and replace them by a corps d’élite selected from the legions.[415]

This force, still too small to be effective, was further strengthened by an increase in the number of the Equites Singulares,[416] and the addition of one of Severus’s new legions, the Secunda Parthica, which was henceforth stationed at Alba.[417] His successors continued the same policy: under Severus Alexander we find an officer of the Household Troops bearing the title praepositus equitum itemque peditum iuniorum Maurorum,[418] a title which implies the existence of at least two regiments of this character, and the Osroeni sagittarii, who were among this emperor’s following at the time of his murder, were so numerous that they attempted to set up a rival to Maximin and were temporarily disbanded.[419]

Had the construction of a field army on these lines proceeded in time of peace, it would necessarily have involved a reorganization of the whole system to meet the increase in expenditure. As it was, the fifty years of civil war and barbarian invasion which followed the accession of Maximin saw the old order irreparably ruined. The great Illyrian emperors who saved civilization for another century, and spent themselves in marching ceaselessly from province to province, cutting down the hydra heads of revolt and striving to repel the recurring assaults of Goth or Persian, could neither hope to maintain the old frontier lines nor spare time to collect vexillations after the second-century manner when each new danger threatened. Sweeping together Household Troops and fragments of the broken frontier armies and enlisting thousands of barbarian mercenaries, they strove to keep a concentrated force at their disposal which they moved constantly backwards and forwards across the Empire as each internal or external crisis demanded. It was this field army which shared in the imperial triumphs and received such rewards as the exhausted finances could bestow. In comparison with it such units of the old frontier troops, legions and auxilia alike, as maintained their old positions (and we shall see that many did so) sank steadily in prestige and importance. When finally the barbarian fury had temporarily spent its force, and a cessation of internal warfare granted Diocletian and Constantine breathing space in which to reorganize the civil and military administration of the Empire, the provisional reconstruction brought into being by these fifty years of stress and disaster was formally recognized and incorporated in the new order. The distinction between first and second class troops is no longer between legions and auxilia as in the days of Augustus, but between the Palatini and Comitatenses on the one hand, who followed in war the emperor himself and the new heads of the military hierarchy, the magistri peditum and equitum, and were kept concentrated at strategic points within the Empire in time of peace, and on the other the Limitanei or Ripenses, who formed, under the duces limitum, a territorial frontier guard, membership in which was now hereditary in law as well as practice.[420]

At this point we might legitimately take leave of our subject, for although the names of many of the old auxiliary regiments still appear in the fourth and fifth centuries among the Limitanei, there is nothing in either character or status to distinguish them from such of the old legions as had survived in a similar capacity. The title ‘auxilia’, on the other hand, is now applied to corps of new creation and barbarian origin which figure on the roll of the field army.

But the very fact that so many of the old corps still figure on the army list tempts us to consider the circumstances under which they survived and to take a brief survey of the changed conditions under which they continued their existence. It is fortunate that for the history of the Roman army during the fourth century we possess two authorities of considerable merit, the historian Ammianus Marcellinus and the Notitia Dignitatum. Ammianus, himself a soldier, is practically the first historian of the Empire since Josephus to give us a first-hand account of military operations.[421] The Notitia Dignitatum purports to give us, what we do not possess for any earlier period, a complete list of the regiments composing the imperial army. It is true that this list appears to be a compilation drawing from evidence of very different dates, but there can be no doubt that it represents for most provinces the general state of things prevailing in the fourth century.

The most significant fact which strikes us in these authorities is the barbaric character of both troops and officers. The majority of the officers mentioned by Ammianus, even those of highest rank, are of Teutonic origin, many being drawn even from the Franks, who are usually reckoned among the more uncivilized of the Empire’s assailants. The same picture is presented by the Notitia. Corps which must at any rate have been originally raised from barbarian tribes, who normally dwelt beyond the frontier, abound among the Palatini and Comitatenses, and are to be found in smaller number among the Limitanei. Thus barbarian Atecotti from Caledonia figure as auxilia palatina in the field armies of Illyricum, Italy, and Gaul;[422] cavalry drawn from the Alani appear as a vexillatio palatina in Italy,[423] and Marcomanni as a vexillatio comitatensis among the troops assigned to the comes Africae.[424] Among the troops of the second class we find in the garrison of Egypt Vandals, Iuthungi, and Quadi from the Danube, Franks and Chamavi from the Lower Rhine, Tzanni and Abasgi from the Caucasus,[425] and much the same elements appear in the garrison of Phoenicia.[426] In regard to these troops it may be urged that, since they are organized in cohorts and alae after the old model, they seem to have been incorporated at latest towards the end of the third century, and that such corps, since they can hardly have obtained fresh drafts from their original recruiting-grounds, may have undergone the same transformation as the regiments of Spaniards and Gauls which were sent to Egypt and Syria in the first century. In the case in question this argument may possibly hold good,[427] but in other parts of the Empire it was no longer necessary to send recruiting agents beyond the borders to find barbarian troops. In recording the presence of a praefectus Sarmatarum gentilium in almost every considerable town in North Italy,[428] and of similar officers commanding German laeti in all the provinces of Gaul, the Notitia[429] is but confirming the abundant evidence of other authorities as to the settlement of barbarians within the Empire during the third and fourth centuries.[430]

This wholesale use of barbarians was largely due to the hasty constructive measures which the stress of the third-century invasions demanded. The normal recruiting-grounds of the army were the first to be desolated, and after a costly campaign it was easier to fill the depleted ranks by enlisting barbarian prisoners than to raise and train levies from the unwarlike provinces of the interior. In the same way it seemed statesmanlike to settle other prisoners on the deserted fields, who, secure themselves in their tenure, might aid in repelling their successors. Thus the number of barbarian contingents was constantly increasing, and behind the banners of Aurelian or Probus the Teutonic war-band marched side by side with regiments which could claim a record extending back to the reign of Augustus. The only considerable levies made within the Empire after 250 were carried out in the Illyrian provinces of which most of the emperors were natives, and are represented by the fifty or sixty regiments of Dalmatian cavalry which appear in the Notitia stationed in almost every province.[431]

But side by side with the new creations, such as the Felices Honoriani and the Comites Taifali, the names of many of the old corps still figure on the fourth-century army list. The legions had naturally come off best; the most determined barbarian raid seldom took a legionary fortress, and if it did, a detachment serving with the field army would probably survive to keep the name of the corps in existence. It is not surprising, therefore, to find that of the thirty legions which existed before the reign of Severus, twenty-seven still appear in the Notitia.[432] From the way in which they are mentioned, however, we can gather many evidences of the storm through which the army had passed. Many detachments, severed from the main body on some special service, were never able to regain it, and are found where the fortunes of war had stranded them. Thus Legio VII Gemina not only appears in its proper place, divided between the field army and the territorial forces of Spain, but is also mentioned as a Legio Comitatensis in the field army of the East, and a Legio Pseudo-comitatensis in Gaul.[433] The old Dacian legion, XIII Gemina, is represented by several detachments guarding that part of the Danube which was allotted to the new province of Dacia Ripensis, but appears also in Egypt.[434] Legio II Italica, which had guarded Noricum since the days of Marcus, is included also as a Legio Comitatensis in the field army of Africa.[435]