[147] Studies in Roman History, Second Series, p. 112.
[148] What exactly this amounted to is difficult to make out. It would be natural to suppose a system of military districts within the province. In Britain, for instance, the line between Tyne and Solway, with the auxilia upon it, might have been divided between Legio VI Victrix from York and Legio XX Valeria Victrix from Chester. Unfortunately the epigraphical evidence does not support the idea that the activity of the two legions was localized in this way. The point is obscure and would not have been worth such a detailed discussion but for the unwarrantable facility with which it is usually disposed of.
[149] Tac. Ann. iv. 5 ‘At apud idonea provinciarum sociae triremes alaeque et auxilia cohortium, neque multo secus in iis virium: sed persequi incertum fuit, cum ex usu temporis huc illuc mearent, gliscerent numero et aliquando minuerentur’. The sociae triremes, i.e. the Rhine fleet, &c., counterbalance the Italian fleets at Ravenna and Misenum.
[150] Velleius, ii. 113.
[151] The number of legions existing at this date is not absolutely certain, but it seems most probable that there were twenty-eight. Cf. von Domaszewski in the Römisch-germanisches Korrespondenzblatt, 1910, on the date of the creation of legions XXI and XXII.
[152] Tac. Hist. ii. 58.
[153] Josephus, Bell. Iud. iii. 4. 66. Twenty-three cohorts (of which ten, an unusually high proportion, were miliariae) and six alae, of unspecified size. That the auxilia had been very largely drawn on is shown by the fact that Titus in 70, although he had a whole additional legion and detachments from two others, had only twenty cohorts and eight alae; Tac. Hist. v. i.
[154] Tac. Hist. iii. 2. The garrison of Noricum is probably not included.
[155] This is on the supposition that the auxilia would have been drawn upon in the same proportion as the legions. Some of the regiments which remained behind seem to have been very much weakened, others such as the Ala Picentiana and the Ala Batavorum probably remained fairly intact. Tac. Hist. ii. 89, iv. 15, 18, 62. Vitellius may have had some of the British auxilia with him (cf. Tac. Hist. ii. 100, iii. 41), but these are more than counterbalanced by the eight Batavian cohorts which had been sent back.
[156] For the provenance of these regiments, particularly the large levies made by Trajan in the Eastern provinces, see the following section.