Diocletian, properly Gaius Aurelius Valerius Diocletianus AD245-313
Roman emperor

He was born of humble parentage near Salona, Dalmatia. He served under Probus, Aurelian and Carus, and was proclaimed Emperor by the army (AD284). To aid him against barbarian attacks he made Maximian his co-Emperor over the Western Empire (286), and also pronounced Constantius Chlorus and Galerius Caesars (292). Diocletian ruled the East from Nicomedia, Maximian ruled Italy and Africa, Constantius Britain, Gaul and Spain, and Galerius Illyricum and the valley of the Danube. Britain, after maintaining independence under Marcus Aurelius Carausius and Allectus, was restored to the empire (296), the Persians were defeated (298), and the Marcomanni and other northern barbarians were driven beyond the Roman frontier. Diocletian's domestic reforms displayed his genius for administration. He strengthened the frontiers, increased the size of the army, revised legal codes, instituted new taxes and restored a sound coinage. A conservative, he attempted to preserve the ancient Roman virtues, but this led to severe persecution of the Christians (303). Diocletian and Maximian abdicated (305), and Diocletian retired to Salona (now Split) to philosophy and gardening.

Bibliography: Stephen Williams, Diocletian and the Roman Recovery (1985)