The question arises as to why the Romans allowed their citizen cavalry to lapse in this way, given its record as a highly effective and useful force. The main reason is probably the limited pool of available equites and First Class members. The equites had long since become exclusively an officer class (a role they retained throughout the Principate), as the empire had become simply too large and complex for aristocrats to serve as ordinary troopers. At the same time, many of the First Class of commoners had developed major business interests and had little time for military service. Although commoners of the lower classes could, of course, have been recruited and trained as cavalrymen in larger numbers, that must have seemed costly and unnecessary when subject countries such as Gaul, Spain, Thrace and Numidia contained large numbers of excellent native cavalry which could be employed at much lower pay than citizens.
