§ 2. Military Organisation
The principal features in which the military establishment of the fourth century31 differed from that of the Principate were the existence of a mobile field army, the organisation of the cavalry in bodies independent of the infantry, and the smaller size of the legionary units.
Diocletian had created, and Constantine had developed, a field army in which the Emperor could move to any part of his dominion that happened to be threatened, while at the same time all the frontiers were defended by troops permanently stationed in the frontier provinces. The military forces, therefore, consisted of two main classes: the mobile troops or comitatenses, which accompanied the Emperor in his movements and formed a “sacred retinue” (comitatus); and the frontier troops or limitanei.
The strength of the old Roman legion was 6000 men. The legion of this type was retained in the case of the limitanei; but it is broken up into detachments of about 1000 (corresponding to the old cohort), which are stationed in different quarters, sometimes in different provinces. And these detachments are no longer associated with a number of foot-cohorts and squadrons of horse, as of old, when the legatus of a legion commanded a body of about 10,000 men. The cavalry and the cohorts are under separate commanders.32
The field army consisted of two classes of troops, the simple comitatenses and the palatini.33 The palatini, who took the place of the old Praetorian guards, were a privileged section of the comitatenses and retained the special character of Imperial guards, in so far as most of them were stationed in the neighbourhood of Constantinople or in Italy.34 The infantry of the field army was composed of small legions of 1000, and bodies of light infantry known as auxilia which were now mainly recruited from Gauls, and from Franks and other Germans. The cavalry, under a separate command, consisted of squadrons, called vexillationes, 500 strong.
Each of these units,— the legion, the auxilium, the vexillatio of the comitatenses, the legionary detachment, the cohort of the limitanei,— was as a rule under the command of a tribune, in some cases of a praepositus.35 The tribune corresponded roughly to the modern colonel.
All these armies were under the supreme command of Masters of Soldiers, magistri militum. The organisation of this command in the east, as it was finally ordered by Theodosius I, differed fundamentally from that in the west. In the east there were five Masters of Horse and Foot. Two of these, distinguished as Masters in Presence (in praesenti, in immediate attendance on the Emperor), resided at Constantinople, and each of them commanded half of the Palatine troops. The three others exercised independent authority over the armies stationed in three large districts, the West, Thrace, and Illyricum.36
It was otherwise in the west. Here instead of five co-ordinate commanders we find two masters in praesenti, one of infantry and one of cavalry. The Master of Foot was the immediate commander of the infantry in Italy and had superior authority over all the infantry of the field army in all the dioceses, and also over the commanders of the limitanei. In the dioceses the commanders of the comitatenses had the title of military counts.37
According to this scheme the Master of Horse in praesenti was co-ordinate with the Master of Foot. But this arrangement was modified by investing the Master of Foot with authority over both cavalry and infantry; he was then called Master of Horse and Foot, or Master of Both Services, magister utriusque militiae, and had a superior authority over the Master of Horse. In the last years of Theodosius the command of the western armies was thus centralised in the hands of Stilicho, and throughout the fifth century this centralisation, giving enormous power and responsibility to one man, was, as we shall see, the rule.
The limitanei were under the command of dukes, the successors of the old legati pro praetore of the Augustan system. In the west the duke was subordinate to the Master of Foot; in the east to the Master of Soldiers in the military district to which his province belonged.38
The Palatine legions were the successors of the old Praetorian guards, but Constantine or one of his predecessors organised guard troops who were more closely attached to the Imperial person.39 These were the Scholae, destined to have a long history. We associate the name of School with the ancient Greek philosophers, who gave leisurely instruction to their schools of disciples in Athenian porticoes. It was applied to Constantine’s guards because a portico was assigned to them in the Palace40 where they could spend idle hours waiting for Imperial orders. The Scholarians were all picked men, and till the middle of the fifth century chiefly Germans; mounted, better equipped and better paid than the ordinary cavalry of the army. There were seven schools at Constantinople, each 500 strong41 and commanded by a tribune who was generally a count of the first rank.42 We have already seen that the whole guard was under the control of the Master of Offices. Closely associated with the Scholarians was a special body of guards, called candidati from the white uniforms which they wore.
While the Scholarians and Candidates were in a strict sense bodyguards of the Imperial person and never left the Court except to accompany the Emperor, there was another body of guards, the Domestici, consisting both of horse and foot, who as a rule were stationed at the Imperial Court, but might be sent elsewhere for special purposes.43 They were under the command of Counts (comites domesticorum) who were independent of the Master of Soldiers.44 It will be observed that most of the new military creations of the third and fourth centuries had names indicating their close relation to the autocrat, comitatenses, soldiers of the retinue; palatines, soldiers of the palace; domestics, soldiers of the household.
The army of this age had a large admixture of men of foreign birth, and for the historian this perhaps is its most important feature. In the early Empire the foreigner was excluded from military service; the legions were composed of Roman citizens, the auxilia of Roman subjects. Every able-bodied citizen and subject was liable to serve. Under the autocracy both these principles were reversed. The auxilia were largely recruited from the barbarians outside the Roman borders; new troops were formed, designated by foreign names; and the less civilised these soldiers were the more they were prized.45 Some customs and words46 illustrate the influence which the Germans exercised in the military world. The old German battle-noise, the barritus, was adopted as the cry of the Imperial troops when they went into battle. The custom of elevating a newly-proclaimed Emperor on a shield was introduced by German troops in the fourth century. It would be interesting to know how many Germans there were in the army. The fact that most of the soldiers whom we know to have held the highest posts of command in the last quarter of the fourth century were of German origin speaks for itself.
The legions continued to be formed from Roman citizens; but the distinction between citizens and subjects had disappeared since the citizenship had been bestowed, early in the third century, upon all the provincials, and it was from the least civilised districts of the Empire, from the highlands of Illyricum, Thrace, and Isauria, from Galatia and Batavia, that the mass of the citizen soldiers were drawn. From a military point of view highly civilised provinces like Italy and Greece no longer counted. The legions and citizen cavalry ceased to have a privileged position. For instance, the auxilia on the Danube frontier, who were chiefly of barbarian race, were superior in rank to the legionary troops under the same command.
It was a natural consequence of this new policy, in which military considerations triumphed over the political principle of excluding foreigners, that the other political principle of universal liability to service should also be relinquished. It was allowed to drop. In the fifth century