Our knowledge of the different ranks and functions in the Roman imperial army derives, in large part, from Alfred von Domaszewski's study of the Rangordnung ('hierarchy'). When he came to study the a/ae, or cavalry squadrons, he noted that the hierarchy of command was similar to that of the equites singulares Augusti (see AW XI11.3). In fact, the only difference, as far as he could see, was that musicians, present in the emperor's horse guard, were unknown in the regular cavalry units - an odd state of affairs, given that the horse guard was modelled on the auxiliary alae. But, in fact, this was just another reminder of the vagaries of the archaeological record, for we now know of several cavalry musicians (and see also AW XIV.1).
Cavalry command
Domaszewski's doctoral thesis in 1881 had been a study of Hyginus' of a Camp, so he was well aware of the command structure of the ala, since
