DIOCLETIANUS (Caius Valerianus), at first named Diocles, a native of Diocles, in Dalmatia, the town from which he took his surname.--Born A.D. 254, of an obscure family, that circumstance did not, when he had obtained the empire, deter him from pretending to have descended from Claudius II. He had become an able general, and commanded the legions in Maesia, under Probus. Having risen to the highest military dignities, he followed Carus, in that emperor 's Persian campaign, A.D. 283; and was made consul suffectus, the same year. After the death of Carus, he was of the number of those who attached themselves to Numerianus. In 284 he was declared Augustus at Chalcedon, by the army of the East, after the assasination of Numerianus; and he slew with his own hand Arrius Aper, prefect of the pretorians, who had taken part in the murder of that good young prince, which happened the following year. In possesion of the purple, he immediately created Maximianus Caesar; and towards the close of the year, set out for the East. [Here commences the celebrated era of Diocletian, also called the era of martyrs].--The same year he prepared to wage war against Carinus.--A.D. 285, Diocletian was consul for the second time; same year he gave battle to Carinus, near Widdin, in Bulgaria (Viminacium, in upper Maesia). At the first encounter, Diocletian had the worst of it; but Carinus having been killed by his own people, Diocletian gained a victory, thus become, and found himself sole master of the Roman world.--In 286 of aera, being at Nicomedia, in Bythina, he proclaimed as Augustus, and associated with himself in the empire, Maximianus, afterwards surnamed Herculius, to whom he assigned the government of the Wastern provinces, reserving for himself the administration of affairs in the East. The new Augustus entered actively upon his duties, by proceeding into Gaul, and suppressing an insurrection raised there by AElianus and Amandus--Diocletian served the consulate for the third time, 287. Maximianus defeated the Germans, who had invaded Gaul, and drove them back beyond the Danube (288).
After vain efforts made against Carausius, who had proclaimed himself Emperor in Britain, the two Augusti gave that island to the successful usurper. In 290, Diocletian served his fourth consulship. In 291, he regulated affairs in those provinces of the empire which he had retained to him self. In addition to the old dangers of barbarian incursions, new perils had vegun to manifest themselves--namely, in the East, on the part of the Persians: in Africa, on the part of the Manritanians, called Quinquegentari; in Egypt, from a pretender to the purple named Achilleus: Diocletian, therefore, being at Nicomedia, March 1, A.D. 292, declared caesars Constantius Chlorus and Galerius Maximianus, and decided that he, Diocletianus Hovius, should govern the East, and that his colleague Maximianus Herculius should govern Italy, Africa, and the Isles, whilst Thrace and Illyria were assigned to Galerius, and the Gallic provinces together with Britain, Spain, and Mauritania, with Costantius Chlorus. In 293 Diocletian was consul for the fifth time, and Allectus slain, the province of Britain returned under the yoke of the emperors. In 297, Diocletian sent Galerius against Narses, King of the Persians, who was at first victorious, but the war ended triumphantly for Galerius. The seventh and eighth consulates of Diocletian took place in 198 and 303. At the commencement of the latter year, at the instigation of Galerius, Diocletian ordered at Nicomedia a persecution against the Christians. Soon afterwards he departed for Rome, where he and Maximianus Herculins jointly enjoyed the honors of a triumph for victories over the enemy gained since their accession to the empire.--A.D. 304. Diocletian, vonsul for the ninth time, returned to Nicomedia, disordered in body and wretched in mind. In 305, advised or compelled by Galerius Maximian, Diocletian, enfeebled perhaps by sickness, and tired of power and its increasing anxieties, abdicated the government, at Nicomedia. The same day, following his senior colleague 's example, Maimianus Herculius laid down the purple at Milan. Galerius and Constantius Chorus were declared Augusti; Severus and Maximinus Daza, Caesars.