120 THE ROMAN DOMINION ascendency over the others. Later still he could even resign the Imperial authority altogether with a certainty that he could re- sume it to the universal satisfaction if he should see fit to do so. Diocletian in fact saw that an empire having so vast a line of Partition frontier open to attack by vast and ever-increasing of the Empire, masses of foes could not possibly be administered effectively by one man. He parted the empire into four great divisions : the eastern, which included Rome and Asia and Egypt, with the Thracian portion of the eastern European peninsula; two central divisions, which included the rest of Greece, Illyria, Italy, and North Africa; and a western division, which comprised Britain, Gaul, and Spain. The eastern division he took into his own charge, while retaining only a very general supremacy over the colleagues to whom the other three divisions were entrusted. Diocletian and his senior colleague bore the title of Augustus, while the two juniors were called Caesars. Each had his own capital; all the four men were Illyrians. The western Caesar was Constantius, whose son Constantine ultimately became sole emperor. The four emperors were all capable rulers and able soldiers, and for the time the new machinery worked effectively. After nearly twenty years, all with the exception of Constantius, joined in a fierce persecution of the Christians. In this, how- ever, Constantius himself refused to participate. Helena, the Rise of mother of his son Constantine, was actually a Chris- Constantine. t j an# At the end of twenty years the two Augusti resigned. Constantius died, and was succeeded by Constantine as western Caesar. Before long, however, acute rivalries arose 4 The Chris- amon § various claimants to the titles of Augustus tian Empire, and Caesar. This led to a war between Constantine 312 a.d. an( j Qne f the claimants Maxentius, which was terminated by the decisive battle of the Milvian Bridge in the neighbourhood of Rome. According to his own statement Constantine himself had seen in the heavens a flaming cross bearing the legend, ' Under this standard thou shalt conquer.' It is doubtful whether it can be properly said that Constantine became Christian. But a year after the victory which had made him*acknowledged master of the western half of the empire, he
