[32] For the Helvetii see Tac. _Hist._ i. 67 ‘castelli quod olim Helvetii suis militibus ac stipendiis tuebantur’. The Raetian militia are mentioned in the following chapter: ‘Raeticae alae cohortesque et ipsorum Raetorum iuventus, sueta armis et more militiae exercita.’ It is quite clear that there were in the province (_a_) regular auxiliary regiments; (_b_) a native militia. I do not understand Professor Reid’s statement (_The Municipalities of the Roman Empire_, p. 203) that ‘the troops maintained there were not Roman legions with regular auxiliaries but contingents of allied forces’. [33] Tac. _Hist._ ii. 69 ‘reddita civitatibus Gallorum auxilia, ingens numerus et prima statim defectione inter inania belli adsumptus’. THE AUXILIA DURING THE FIRST TWO CENTURIES A.D. SECTION I THE STRENGTH AND ORGANIZATION OF THE AUXILIARY REGIMENTS From the death of Augustus to the period when the frontier defences first began to collapse under the strain of the barbarian invasions, more than two centuries later, the imperial army presents a picture of military conservatism unrivalled in history. Not only does the original distinction between the legions of _cives Romani_ and the auxilia of _peregrini_ remain throughout the basis of its organization, but even individual corps show a marvellous power of vitality. Dio Cassius, writing at the beginning of the third century, notes that, of the twenty-five legions in existence in 14, eighteen still survived in his own day, and epigraphical evidence shows that scores even of the more easily destructible auxiliary regiments could claim as long a record. In appearance, indeed, the only considerable change introduced into the organization of the auxilia during this period was the addition of the _numeri_ in the second century to the _alae_ and _cohortes_ which had previously been the only units employed. It is true, of course, that this conservatism was in some respects rather superficial, and that, while administrative forms and nomenclature remained unaltered, in more essential matters the army had been deeply affected by the tendencies of the age. It is still, however, possible, while paying due attention to these changes, to treat the two centuries which follow the death of Augustus as a single period in the history of the auxilia; it is only amid the confusion caused by the barbarian invasions of the third century and the subsequent attempts at reorganization that we definitely lose sight of our old landmarks. Leaving out of account for the moment the _numeri_, which, as late creations with a special significance, are reserved for future discussion, let us commence with the _alae_ and _cohortes_, which remained throughout this period the units of auxiliary cavalry and infantry respectively.