The period to be studied in this chapter extends roughly from the middle of the third century to the middle of the fifth century A.D. Looked at from the point of view of the history of the Roman Empire it can be divided into several stages. The first extends from the death of Alexander Severus in 235 to the proclamation of Diocletian as emperor in 284. This was a half-century of chaos and disorder throughout the empire. The delicate balance of political power broke down, and legitimacy was no longer conferred upon emperors by a consensus, however formal, of Senate, people and army, and sustained by the general consent of the ruling classes of the cities in both east and west. Local interest groups began to proclaim their own candidates for imperial power. The most effective of these were the provincial armies and to a lesser degree the Praetorian Guard at Rome. The half-century of disorder was begun by the assassination of Alexander Severus at Moguntiacum (Mainz) and the proclamation by the army there of Maximinus, a Thracian officer who had risen from the ranks. Soon the influential land-owning class of Africa proclaimed their candidate, Gordian. The powerless Senate vacillated between the two claimants and for a time put forward its own candidates, Balbinus and Pupienus. And so it went on. The situation was one of almost permanent civil war, marked not only by several pitched battles between Roman armies, but also by a break-down of civil administration and legality and the growth of arbitrary rule by military commanders, who could maintain their armies in being only by letting them live directly on the produce of the citizens they were supposed to defend.