Details of Troops.—(A) The legion of the Empire was what Marius had left it-6,000 heavy infantry divided into ten cohorts: Augustus added only i 20 horsemen to serve as despatch-riders and the like. The supreme command was no longer in the hands of the six tribunes. According to a practice which had sprung up in the latest Republic it was in the hands of a legatus legionis, deputy of the general (now of the emperor, commander-in-chief of the whole army) and a man usually of senatorial rank and position. The six tribunes assisted him in theory; in practice they were now little more than young men of good birth learning their business or wast ing their time. The real officers of the legion were the 6o centu rions, men who (at least in the early Empire) generally rose from the ranks, and who knew their work. The senior centurion, Primus pilus, was an especially important officer, and on retirement fre quently became praefectus castrorum, "camp adjutant," or ob tained other promotion. Below the centurions were under-officers, standard-bearers, options, clerks and the like. The men them selves were recruited from the body of Roman citizens (though we may believe that birth-certificates were not always demanded). During the 1st century Italy, and particularly north Italy, pro vided the bulk of the recruits. After A.D. 7o, recruiting in Italy for the legions practically ceased and men were drawn from the Ro manized towns of the provinces. After Hadrian, each province seems to have supplied most of the men for the legion (if any) stationed in it, and so many sons of soldiers born during service (castrenses) flocked to the army that a military caste almost grew up. The term of service was, in full, 20 years, at least in theory, but recruiting was voluntary and when men were short discharges were often withheld. On discharge the ex-legionary received a bounty or land : many coloniae (municipalities) were established in the provinces by certain emperors for the special purpose of tak ing discharged veterans—according to a custom of which the first instances occur in the late Republican age. On the whole, the legionary was still the typical "Roman" soldier. If he was no longer Italian, he was generally of citizen birth, and always of citi zen rank, and his connection with the Empire and the Government was real. Each legion bore a number and a title (e.g., II. Augusta,
III. Gallica). The custom of using such titles and numbers can be detected sporadically in the late Republic, and many titles and numbers then borne by legions passed on into the Empire with the legions themselves. As Augustus gradually became master of the world, he found himself with three armies, his own and those of Lepidus and Antony; from the three he chose certain legions to form his new standing army, and he left these with the titles and numbers which they had previously borne, although that conces sion resulted in three legions numbered III. and two numbered IV., V., VI. and X. respectively. Similar titles and numbers were given to legions raised afterwards either to fill up gaps caused by disas ter or to increase the army.
(B) Besides the legions Augustus developed a new order of auxilia. Auxiliaries (as is said above) had served occasionally in the Republican armies since about 250 B.C., and in the later Re public large bodies of them had been enlisted in the armies of con tending generals. Thus Caesar in Gaul enrolled a division of native Gauls, free men but not citizens of Rome, which ranked from the first in all but legal status as a legion, the "Alaudae," and in due course was formally admitted to the legionary list (legio V.). But this use of non-citizens had been limited in extent and confined in normal circumstances to special troops such as slingers or bow men. This casual practice Augustus reduced, or rather extended, to system, following in many details the scheme of the Republican socii and veiling the novelty under old titles. Henceforward, regi ments of infantry (coliortes) or cavalry (alae), 500 or r,000 strong, were regularly raised (apparently, by voluntary recruiting) from the non-citizen populations of the provinces and formed a force almost equal in numbers (and ultimately much more than equal) to the legions. The men who served in these units were less well paid and served longer than the legionaries ; on their discharge they received a bounty and the Roman franchise for themselves, their wives and children. They were commanded by Roman prae f ecti or tribuni, and were no doubt required to understand Roman orders; they must have generally become Romanized and fit for the citizenship, but they were occasionally (at least in the 1st cen tury A.D.) permitted to retain tribal weapons and methods of fight ing and to serve under the command of tribal leaders, who were at once their chiefs and Roman officers. These auxiliaries provided both the whole of the archers, etc., and nearly the whole of the cavalry of the army; they also included many foot regiments. A peculiar arrangement (to which no exact parallel seems to occur in any other army) was that a cohort of Soo men might include 38o foot and r 20 horse and a cohort of i,000 men or 76o foot and 240 horse (cohors equitata), and an ala might similarly include a proportion of foot (ala peditata). Each regiment bore a number and a title, the latter often derived from the officer who had raised the corps (ala Indiana, raised by one Julius Indus), or, still more often, from the tribe which supplied the first recruits (colzors VII. Gallorum, cohors II. IIispanorum and the like). To what extent recruiting remained territorial is uncertain : after the i st century, probably, the territorial names meant in most cases very little.