_Relation of the auxilia to the legions._ It is perhaps relevant to discuss here a point affecting the auxilia as a whole, namely, their relation to the legions in the general scheme of military organization. It is generally supposed that in those frontier armies which included both classes of troops, a group of auxiliary regiments was definitely attached to each legion, and such phrases as ‘a legion with its attendant auxiliaries’ are common in writers on the military system of the Roman Empire. Evidence as to the exact nature and even the existence of such a connexion is, however, somewhat difficult to find. Tacitus does, it is true, refer to the eight Batavian cohorts, who play such an important part in the events of 69, as _auxilia quartae decimae legionis_, but no other passage can be quoted in the same sense, and the connexion in this case was obviously neither close nor durable.[140] In the comparatively detailed account of the first campaign of Bedriacum, which rests at any rate upon a good military source, there is no suggestion that the auxilia marched or manœuvred in separate groups, each connected with a particular legion. Certainly in the normal order of battle throughout the first century the available auxilia were all massed together either as a first line, or in two flanking divisions to the right and left of the legionaries, and the auxilia of the army which crossed the Rhine in 73 were not divided among the legionary _legati_, but had a commander of their own.[141] Supporters of the legionary connexion also refer to the two diplomata issued in the same year and on the same day (August 14, 99) to two different groups of auxiliary regiments stationed in Moesia Inferior, and suggest that this curious arrangement can best be explained on the supposition that each diploma refers only to the auxilia of one legion.[142] A similar explanation suggests itself for the fact that only one regiment is common to the two British diplomata of 103 and 105.[143] It seems impossible, however, to interpret all the diplomata in this manner. The British diploma of 124, for example, which was issued to men from six alae and twenty-one cohorts, can hardly be supposed to contain the auxilia of only one of the three legions then stationed in the province.[144] In Pannonia Superior also so many regiments are common to the five complete second-century diplomata which we possess that we must, on this theory, refer them all to the auxilia of one and the same legion.[145] How, then, do we account for the fact that the inscriptions of the province hardly mention any regiments but those contained in these diplomata? In other words, why should all our evidence refer to the auxilia of one legion, and those attached to the other two, then stationed in the province, have entirely disappeared?