Diocletian (Docles, Diocles, Caius Valerius Diocletianus Jovius), 284-305. The acts that make the reign of this emperor memorable in the history of the church belong to its closing years. Had he died before 303 he would have taken his place among the rulers whose general tolerance helped Christianity to obtain its victory. As it is, his name is identified with the most terrible of its persecutions. For three centuries men reckoned from the commencement of his reign as from the era of martyrs; and the date is still recognized in the Coptic Church as the basis of its chronology.
The earlier years of Diocletian concern us only in connexion with the struggle
which came to a head when his work seemed nearly over. Elected by the soldiers in Bithynia at the age of 39, after the murder of Numerian, he was formally installed at Nicomedia. In 286 he chose Maximian as his colleague, gave him the title first of Caesar and then of
Augustus, and sent him to command in the West, while he remained in the East, chiefly at Nicomedia, which he tried to make, by lavish outlay on its buildings, a new capital for the empire. It indicates his intention to uphold the religion of the state that he assumed the surname of Jovius, and gave to his colleague that of Herculius. Among the buildings with which he embellished the various provinces were temples of Zeus, Apollo, Nemesis, Hecate, at Antioch, of Isis and Serapis at Rome, of Isis at Phylae, of Mithras at Vindobona. He consulted haruspices and augurs as to the success of his enterprises, and in more difficult emergencies the oracle of the Milesian Apollo at Branchidae (Lactant. de Mort. Pers. cc. 10, 11).
