There were originally no standing forces, but the citizens performed military service like any other civic duty when summoned by the magistrates. The gradual development of a military profession and standing army culminated in the admission of the poorest class to the ranks by Marius (about 107 BC). Henceforth the Roman army was made up of a body of men whose character was essentially that of mercenaries, and whose term of continuous service varied in different divisions from 16 to 26 years.
The forces which composed the Roman army under the Empire may be divided into the following five groups: (1) the imperial guard and garrison of the capital, (2) the legions, (3) the auxilia, (4) the numeri, (5) the fleet. We shall discuss their organization in the order mentioned.
1. The Imperial Guard:
The imperial guard consisted of the cohortes praetoriae, which together with the cohortes urbanae and vigiles made up the garrison of Rome. In the military system as established by Augustus there were nine cohorts of the praetorian guard, three of the urban troops, and seven of the vigiles. Each cohort numbered 1,000 men, and was commanded by a tribune of equestrian rank. The praetorian prefects (praefecti praetorii), of whom there were usually two, were commanders of the entire garrison of the capital, and stood at the highest point of distinction and authority in the equestrian career.
2. The Legions:
There were 25 legions in 23 AD (Tacitus Annals 4, 5), which had been increased to 30 at the time of the reign of Marcus Aurelius, 160-180 AD (CIL, VI, 3492 a-b) and to 33 under Septimius Severus (Dio Cassius, iv. 23-24). Each legion was made up, ordinarily, of 6,000 men, who were divided into 10 cohorts, each cohort containing 3 maniples, and each maniple in turn 2 centuries.
The legatus Augustus pro praetore, or governor of each imperial province, was chief commander of all the troops within the province. An officer of senatorial rank known as legatus Augusti legionis was entrusted with the command of each legion, together with the bodies of auxilia which were associated with it. Besides, there were six tribuni militum, officers of equestrian rank (usually sons of senators who had not yet held the quaestorship) in each legion. The centurions who commanded the centuries belonged to the plebeian class. Between the rank of common soldier and centurion there were a large number of subalterns, called principales, who correspond roughly to the non-commissioned officers and men detailed from the ranks for special duties in modern armies.
3. The "Auxilia":
The auxilia were organized as infantry in cohortes, as cavalry in alae, or as mixed bodies, cohortes equitatae. Some of these divisions contained approximately 1,000 men (cohortes or alae miliariae), but the greater number about 500 (cohortes or alae quingenariae). They were commanded by tribuni and praefecti of equestrian rank. The importance of the auxilia consisted originally in the diversity of their equipment and manner of fighting, since each group adhered to the customs of the nation in whose midst it had been recruited. But with the gradual Romanization of the Empire they were assimilated more and more to the character of the legionaries.
4. The "Numeri":
The numeri developed out of the provincial militia and began to appear in the 2nd century AD. They maintained their local manner of warfare. Some were bodies of infantry, others of cavalry, and they varied in strength from 300 to 90 (Mommsen, Hermes, XIX, 219 f, and XXII, 547 f). Their commanders were praepositi, praefecti or tribuni, all men of equestrian rank.
5. The Fleet:
The fleet was under the command of prefects (praefecti classis), who took rank among the highest officials of the equestrian class. The principal naval stations were at Misenum and Ravenna.
6. Defensive Arrangements:
Augustus established the northern boundary of the Empire at the Rhine and at the Danube, throughout the greater part of its course, and bequeathed to his successors the advice that they should not extend their sovereignty beyond the limits which he had set (Tacitus Annals i.11; Agricola 13); and although this policy was departed from in many instances, such as the annexation of Thrace, Cappadocia, Mauretania, Britain, and Dacia, not to mention the more ephemeral acquisitions of Trajan, yet the military system of the Empire was arranged primarily with the view of providing for the defense of the provinces and not for carrying on aggressive warfare on a large scale. Nearly all the forces, with the exception of the imperial guard, were distributed among the provinces on the border of the Empire, and the essential feature of the disposition of the troops in these provinces was the permanent fortress in which each unit was stationed. The combination of large camps for the legions with a series of smaller forts for the alae, cohorts, and numeri is the characteristic arrangement on all the frontiers. The immediate protection of the frontier was regularly entrusted to the auxiliary troops, while the legions were usually stationed some distance to the rear of the actual boundary. Thus the army as a whole was so scattered that it was a difficult undertaking to assemble sufficient forces for carrying out any considerable project of foreign conquest, or even to cope at once with a serious invasion, yet the system was generally satisfactory in view of the conditions which prevailed, and secured for the millions of subjects of the Roman Empire the longest period of undisturbed tranquillity known to European history.
7. Recruiting System:
In accordance with the arrangements of Augustus, the cohortes praetoriae and cohortes urbanae were recruited from Latium, Etruria, Umbria, and the older Roman colonies (Tacitus Annals 4, 5), the legions from the remaining portions of Italy, and the auxilia from the subject communities of the Empire (Seeck, Rheinisches Museum, XLVIII, 616).
But in course of time the natives of Italy disappeared, first from the legions, and later from the garrison of the capital. Antoninus Plus established the rule that each body of troops should draw its recruits from the district where it was stationed. Henceforth the previous possession of Roman citizenship was no longer required for enlistment in the legions. The legionary was granted the privilege of citizenship upon entering the service, the auxiliary soldier upon being discharged (Seeck, Untergang der antiken Welt, I, 250).
II. Allusions in the New Testament to the Roman Military Establishment.
Such references relate chiefly to the bodies of troops which were stationed in Judea. Agrippa I left a military establishment of one ala and five cohorts at his death in 44 AD (Josephus, Ant, XIX, ix, 2; BJ, III, iv, 2), which he had doubtless received from the earlier Roman administration. These divisions were composed of local recruits, chiefly Samaritans (Hirschfeld, Verwaltungsbeamte, 395; Mommsen, Hermes, XIX, 217, note 1).
The Ala I gemina Sebastenorum was stationed at Caesarea (Josephus, Ant, XX, 122; BJ, II, xii, 5; CIL, VIII, 9359).
1. Augustan Band:
Julius, the centurion to whom Paul and other prisoners were delivered to be escorted to Rome (Ac 27:1), belonged to one of the five cohorts which was stationed at or near Caesarea. This Speira Sebaste (Westcott-Hort), "Augustus' Band" (the Revised Version (British and American) "Augustan band"; the Revised Version, margin "cohort"), was probably the same body of troops which is mentioned in inscriptions as Cohors I Augusta (CIL, Supp, 6687) and Speira Augouste (Lebas-Waddington 2112). Its official title may have been Cohors Augusta Sebastenorum (GVN). It will be observed that all divisions of the Roman army were divided into companies of about 100 men, each of which, in the infantry, was commanded by a centurion, in the cavalry, by a decurion.
2. Italian Band:
There was another cohort in Caesarea, the "Italian band" (Cohors Italica, Vulgate) of which Cornelius was centurion (Ac 10:1: ek speires tes kaloumenes Italikes). The cohortes Italicae (civium Romanorum) were made up of Roman citizens (Marquardt, Romische Staatsverwaltung, II, 467).
3. Praetorian Guard:
One of the five cohorts was stationed in Jerusalem (Mt 27:27; Mr 15:16), the "chief captain" of which was Claudius Lysias. His title, chiliarchos in the Greek (Ac 23:10,15,17,19,22,26; 24:7 the King James Version), meaning "leader of a thousand men" (tribunus, Vulgate), indicates that this body of soldiers was a cohors miliaria. Claudius Lysias sent Paul to Felix at Caesarea under escort of 200 soldiers, 70 horsemen, and 200 spearmen (Ac 23:23). The latter (dexiolaboi, Westcott and Hort, The New Testament in Greek) are thought to have been a party of provincial militia. Several centurions of the cohort at Jerusalem appear during the riot and subsequent rescue and arrest of Paul (Ac 21:32; 22:25-26; 23:17,23). The cohortes miliariae (of 1,000 men) contained ten centurions. A centurion, doubtless of the same cohort, was in charge of the execution of the Saviour (Mt 27:54; Mr 15:39,44-45; Lu 23:47). It was customary for centurions to be entrusted with the execution of capital penalties (Tacitus Ann. i.6; xvi.9; xvi.15; Hist. ii.85).
The the King James Version contains the passage in Ac 28:16: "The centurion delivered the prisoners to the captain of the guard" (stratopedarches), which the Revised Version (British and American) omits. It has commonly been held that the expression stratopedarches was equivalent to praetorian prefect (praefectus praetorius), and that the employment of the word in the singular was proof that Paul arrived in Rome within the period 51-62 AD when Sex. Afranius Burrus was sole praetorian prefect. Mommsen (Sitzungsberichte der Berliner Akademie (1895), 491-503) believes that the sentence in question embodies an ancient tradition, but that the term stratopedarches could not mean praefectus praetorius, which is never rendered in this way in Greek. He suggests that it stands for princeps castrorum peregrinorum, who was a centurion in command of the frumentarii at Rome. These were detachments of legionary soldiers who took rank as principales. They served as military couriers between the capital and provinces, political spies, and an imperial police. It was probably customary, at least when the tradition under discussion arose, for the frumentarii to take charge of persons who were sent to Rome for trial (Marquardt, Romische Staatsverwaltung, II, 491-94).
LITERATURE.
Comprehensive discussions of the Roman military system will be found in Marquardt, Romische Staatsverwaltung, II, 319-612, and in Pauly-Wissowa, Realencyclopadie, article "Exercitus."
George H. Allen