 By the late 4th century, the Empire had become chronically deficient in raising sufficient troops from amongst its own population. As an alternative, taxation raised internally was increasingly used to subsidise growing numbers of barbarian recruits. The Romans had, for some time, recruited individual non-Roman soldiers into regular military units. In 358 AD, this practice was accelerated by the wholescale adoption of the entire Salian Franks people into the Empire, providing a ready pool of such recruits. In return for being allowed to settle as foederatii in northern Gallia on the near side of the Rhine, the Franks were expected to defend the Empire's borders in their territory and provide troops to serve in Roman units.
