The Auxilia of the Roman Imperial Army

by George Leonard Cheesman

The course of the second century saw the auxilia still more firmly established as an essential part of the republican military system. Before its close the Roman and Italian cavalry had entirely disappeared; the changes in the condition of military service, in particular the tedious and unprofitable Spanish campaigns, made the members of the upper classes, among whom the cavalry had been recruited, increasingly reluctant to take their places in the ranks as private soldiers. After the reforms of Marius the legion had no cavalry attached to it, and if the Italian contingents still existed they must likewise have disappeared when, in consequence of the extension of the franchise in 90 and 89 B.C., the former socii were all enrolled in the legions. From this moment the Roman generals depended for their cavalry upon the auxilia alone.[6] In the case of the light-armed troops the same process took place, although here military rather than political reasons probably predominated. The last recorded use of the velites, the old national light infantry, is during the war against Iugurtha, and they were probably abolished by Marius.[7] There is certainly no instance of any but auxiliaries being employed as light troops during the following century. From these considerations it necessarily follows that when, during the last fifty years of the Republic, a standing army came into existence, a number of auxiliary regiments formed part of it. When Caesar mentions that he had Cretan archers, Balearic slingers, and Numidian cavalry under his command so early as the beginning of his second campaign, we can hardly doubt that these regiments had formed part of the regular troops which he found in the province.[8]

Thus before the end of the Republic we have the chief feature of the military system of the Empire, the division of the army into the legions of cives Romani and the auxiliary light troops and cavalry supplied by the unenfranchised provincials, already in existence. Even the practice of conferring the civitas upon troops of this class as a reward for military service was resorted to by the Republic, although probably only under exceptional conditions. We possess a document recording a grant of this nature to some Spanish auxiliaries, members of a turma Salluitana which had distinguished itself at the siege of Asculum in 89 B.C.[9]

There is no evidence, however, that this branch of the service escaped the effects of the inefficiency in administration which characterized the last generation of the republican régime. Certainly too few regiments of this class were kept on a permanent footing, and a general of the period either had to take the field with far too small a proportion of cavalry and light infantry, or make up the deficiency by hasty levies called out in the districts nearest to the scene of operations. Caesar, for example, started the campaign of 58 B.C. with a totally insufficient number of regular auxiliaries, and during the following years was forced to make up his deficiency in cavalry by demanding contingents, which were often of more than doubtful fidelity, from the Gallic tribes which successively submitted to his arms. To supplement these he also raised a corps of German mercenaries and largely increased it later after the defection of the majority of the Gallic contingents to Vercingetorix.[10]

The civil wars saw a large increase in the numbers of the auxilia. Caesar set the example by leading off thousands of his Gallic cavalry, with the object, doubtless, of using them as hostages for their compatriots’ fidelity as well as of increasing his army. Pompeius followed suit and endeavoured to make up for the loss of the Italian recruiting ground by enrolling auxilia from the Eastern provinces in large numbers. The Gallic cavalry proved a great success; in the campaign of Thapsus they showed marked superiority to the African light horse, previously accounted supreme in cavalry warfare,[11] and the death of Caesar found them still serving in large numbers in every part of the Empire. At least those who are found, together with Lusitanians and Spaniards, in the army of Brutus and Cassius during the Philippi campaign must have been stationed either in Macedonia or the East before hostilities began.[12]

We can thus see that when the battle of Actium in 31 B.C. placed the forces of the Roman world in the hands of Augustus, the main lines on which the military system of the Empire was based were already clearly marked, and his great work of reorganization, while importing everywhere order and principle into existing practice, involved no breach with the military traditions of the past. To say this is in no sense to minimize his achievement. It must be remembered that while individual generals, such as Lucullus, Pompeius, or Caesar, had brought their armies to a high pitch of efficiency, the general military administration of the late republic had been chaotic in the extreme. Here, as elsewhere, the real issues were resolutely evaded, and in case of need a crisis had to be met by hasty and inefficient improvisation. Although a standing army had existed in practice for fifty years it was never accepted in principle, and no attempt was made to assess the military requirements of the state and see that an efficient force of the proper strength was maintained. With similar lack of foresight the Senate refused to admit the principle of granting a donative on discharge, while repeatedly granting it under pressure, thus weakening the control of the central government over troops in the field and increasing the chances of a military pronunciamento. In consequence, the wars of this period almost invariably begin with disasters in the field, owing to the inadequacy of the standing army both in numbers and efficiency,[13] and end with a political crisis of greater or less magnitude over the donative grievance, which naturally gave an ambitious general an opportunity of using the support of his troops to further his own ends. The work of Augustus in bringing order out of this chaos, providing forces adequate to the needs of the state, and re-establishing over them the control of the central government, is not the least of his administrative triumphs.

As a preliminary he accepted, as was perhaps inevitable, the principle of a standing army of professional soldiers. This step has of late been severely criticized, especially by admirers of the Continental system, but it is difficult to see how short-service levies could have proved adequate to the defence of frontiers which were, for all practical purposes, more distant from Rome than Peshawur is from Aldershot. The other alternative, to entrust the provincials with the defence of their own borders, was not in harmony with his general policy, nor, it may be said, was the time ripe for such a step. The words which the third-century historian and administrator, Dio Cassius, puts into the mouth of Maecenas in dealing with this question were written doubtless with reference to the conditions of his own time, but they may certainly be applied to the earlier period, and in essence they still hold good to-day.

‘You will be wise to maintain a permanent force (στρατιώτας ἀθανάτους) raised from the citizens, the subjects, and the allies distributed throughout all the provinces in larger or smaller bodies, as necessity requires. These troops must always remain in arms and be drilled constantly; at the most suitable points they must prepare themselves winter quarters, and they must serve for a fixed period calculated to allow them a little freedom after their discharge before old age comes on. For we can no longer rely upon forces called out for the occasion, owing to the distance which separates us from the borders of our Empire and the enemies which we have upon every side. If we allow all our subjects who are of military age to possess arms and undergo a military training, there will be a continual series of riots and civil wars, while if, on the other hand, we check all military activity on their part, we shall run the risk of finding nothing but raw and untrained troops when we need a contingent for our assistance.’[14]

The solution which Augustus found for this problem was then to revise the military system so that, while using as much as possible of the available material, he did not disturb the political conditions on which the equilibrium of the State depended. For it was no part of his intention materially to alter the structure of the Empire as an aggregate of states possessed of greater or less powers of self-government, held together by their subordination to Rome and withheld by their position from any independent external policy. Whatever possibilities he may have contemplated for the future he made himself few attempts to further the process of unification either by reducing the inhabitants of the privileged states to a lower grade or by the more generous policy of making wide extensions of the franchise and creating by this means a new imperial citizenship. This difference of status among the inhabitants of the Empire was naturally reflected in the military system. The cives Romani—that is to say, the inhabitants of Italy and of the few enfranchised communities among the provinces—furnished the new Household Troops, and the greater part, at any rate, of the recruits for the legions, and paid for their superior position as the ruling race by contributing much more heavily in proportion to their numbers than any other class in the population. The nominally independent monarchs of the client kingdoms were allowed and encouraged to maintain armies, often of considerable size, under their own control, and frequently led in person the contingents which they were called upon to bring to the aid of the regular troops when hostilities were taking place near their borders. These contingents were often numerous and capable of rendering valuable service. Thus Rhoemetalces of Thrace assisted in the suppression of the dangerous Pannonian revolt of 6-9, and Ptolemaeus of Mauretania was publicly honoured for his loyal co-operation against the African rebel Tacfarinas.[15] Along the eastern frontier, kingdoms of this type, the wreckage of the old Hellenistic system, were more numerous and played a more important part. Thus Antiochus III of Commagene, Agrippa II, Sohaemus of Emesa, and Malchus of Damascus contributed 15,000 men to the army which Vespasian led into Palestine in the spring of 67.[16] Even the more autonomous city states seem to have retained a militia which was occasionally made use of. So late as the reign of Hadrian, in the army which Arrian led against the Alani, we find a contingent from the ‘free’ city of Trapezus, which is reckoned among the σύμμαχοι as opposed to the regular imperial troops.[17] A similar freedom from the direct control of Roman officers was permitted to the chiefs of some of the border tribes, who were allowed to lead their own clansmen to battle. To this type of militia belong the tumultuariae catervae Germanorum cis Rhenum colentium, including the Batavians under their dux Chariovalda, who serve in the campaigns of Germanicus,[18] and the levies of the Dalmatian clans who started the rebellion of 6.[19]

Last come the permanently embodied regiments raised from the subject communities, the auxilia properly so called, who form the subject of this treatise. Here, probably more than in any other department of the military system of the Empire, we can trace the results of Augustus’s own activity. Regiments of this kind had, as we have seen, existed under the Republic, but they had probably been few in number and the incidence of the levy had been uneven and capricious. Under Augustus not only was the number of regiments largely increased—we hear of no less than fourteen alae and seventy cohorts taking part in the Pannonian War of 6-9[20]—but the inscriptions show us that, with the exception of Greece, always the spoiled child of Roman sentiment, every quarter of the Empire contributed its quota. Details respecting the incidence of this levy on different provinces, and the methods of organization and recruiting, will be found in later sections. It will be sufficient to say here that while the subject communities had probably more reason than any other class to complain of the military demands of the state, the burden was at least more equitably distributed than under the Republic and the total contribution required, in most cases at any rate, not excessive. It is natural to suppose that the fixing of the quota supplied by each community was connected with the drawing up of the census, which placed the taxation of the Empire for the first time on an organized basis, and it seems probable that more evidence might show a reciprocal variation between the two forms of contribution required. We know, for instance, that the Batavians were altogether excused from the payment of tribute on account of the size and value of their contingent, and this case was probably not exceptional.[21]

In all this it is easy to see how much Augustus owes to the institutions of the Republic, and when we come to consider details his debt becomes even more apparent. A standing army consisting of legions of cives Romani and smaller units of peregrini, supported in the field by contingents from allied and nominally independent states, was already in existence. His task was merely to introduce such changes as might obviate the mistakes and failures of the past, and to establish principles which should make for permanence and stability. For in accepting the principle of maintaining a standing army Augustus could not have been blind to the political dangers which this institution brought with it. He endeavoured to meet them by fixing the conditions of service, in particular the sum which a soldier might claim at his discharge, and by establishing a special treasury from which those claims might be satisfied, thus accustoming the troops to look to the central government, not to their generals, for rewards due to them. Moreover, in this department of the state even Augustus allowed no respect for constitutional forms to veil or weaken his authority. When in 69 the legions on the Upper Rhine tore down the imagines of Galba and swore allegiance to the oblitterata iam nomina senatus populique Romani it was a manifest sign that after a century of peace a new period of anarchy had begun.[22]