This chapter argues that the military and political history and prosopography of the early fifth century cannot be reconciled with the existence of the Notitia system. Specifically, the military challenges the east Roman empire faced during this period, most notably Alaric’s depredations in the Balkans, Gaïnas’ revolt in Asia Minor, and attempts to prop up the struggling western empire, all point to a systemic under-militarization in the east that forced Constantinople to rely heavily on barbarian manpower, often with calamitous results. By the 420s, we find evidence for a gradual remilitarization taking place in the east, which set the stage for the major reforms of the 440s.