The first tetrarchy had ended on May 1, 305; the second did not last long. After Constantius died at Eboracum in 306, the armies of Britain and Gaul, without observing the rules of the tetrarchic system, had hastened to proclaim Constantine, the young son of Constantius, as Augustus. Young Maxentius, the son of Maximian (who had never wanted to retire), thereupon had himself proclaimed in Rome, recalled his father into service, and got rid of Severus. Thus, in 307–308 there was great confusion. Seven emperors had, or pretended to have, the title of Augustus: Maximian, Galerius, Constantine, Maxentius, Maximinus Daia, Licinius (who had been promoted Augustus in 308 by Galerius against Constantine), and, in Africa, the usurper Domitius Alexander.
This situation was clarified by successive eliminations. In 310, after numerous intrigues, old Maximian was killed by his son-in-law Constantine, and in the following year Alexander was slain by one of Maxentius’ praetorian prefects. In 311 Galerius died of illness a few days after having admitted the failure of his persecutions by proclaiming an edict of tolerance. There remained, in the West, Constantine and Maxentius and in the East, Licinius and Maximinus Daia. Constantine, the best general, invaded Italy with a strong army of faithful Gauls and defeated Maxentius near the Milvian Bridge, not far from Rome. While attempting to escape, Maxentius drowned. Constantine then made an agreement with Licinius, and the two rallied the Eastern Christians to their side by guaranteeing them religious tolerance in the Edict of Milan (313). This left Maximinus Daia, now isolated and regarded as a persecutor, in a weak position; attacked by Licinius near Adrianople, he fell ill and died soon afterward, in 313. This left the empire with two leaders, Constantine and Licinius, allied in outward appearances and now brothers-in-law as a result of Licinius’ marriage to Constantine’s sister. The reign of Constantine
Constantine and Licinius soon disputed among themselves for the empire. Constantine attacked his adversary for the first time in 316, taking the dioceses of Pannonia and Moesia from him. A truce between them lasted 10 years. In 316 Diocletian died in Salona, which he had never felt a desire to leave despite the collapse of his political creation. Constantine and Licinius then reverted to the principles of heredity, designating three potential Caesars from among their respective sons, all still infants, with the intention of securing their dynasties (two sons of Constantine and one of Licinius). The dynastic concept, however, required the existence of only a single emperor, who imposed his own descendance. Although Constantine favoured the Christians, Licinius resumed the persecutions, and in 324 war erupted once again. Licinius, defeated first at Adrianople and then in Anatolia, was obliged to surrender and, together with his son, was executed. Next, Constantine’s third son, Constantius, was in turn named Caesar, as his two elder brothers, Crispus and Constantine the Younger, had been some time before. The second Flavian dynasty was thus founded, and Constantine let it be believed that his father, Flavius Constantius (Chlorus), was descended from Claudius Gothicus.
Constantine’s conversion to Christianity had a far-reaching effect. Like his father, he had originally been a votary of the Sun; worshiping at the Grand Temple of the Sun in the Vosges Mountains of Gaul, he had had his first vision—albeit a pagan one. During his campaign against Maxentius, he had had a second vision—a lighted cross in the sky—after which he had painted on his men’s shields a figure that was perhaps Christ’s monogram (although he probably had Christ confused with the Sun in his manifestation as summa divinitas [“the highest divinity”]). After his victory he declared himself Christian. His conversion remains somewhat mysterious and his contemporaries—Lactantius and Eusebius of Caesarea—are scarcely enlightening and even rather contradictory on the subject. But it was doubtless a sincere conversion, for Constantine had a religious turn of mind. He was also progressive and greatly influenced by the capable bishops who surrounded him from the very beginning.
Until 320–322 solar symbols appeared on Constantine’s monuments and coins, and he was never a great theologian. Yet his favourable policy toward the Christians never faltered. Christianity was still a minority religion in the empire, especially in the West and in the countryside (and consequently within his own army), thus excluding the possibility of any political calculation on his part. But it was enthusiastically welcomed in the East, and thanks to Constantine the new religion triumphed more rapidly; his official support led to the conversion of numerous pagans, although with doubtful sincerity because they were indifferent in their moral conviction.
The church, so recently persecuted, was now suddenly showered with favours: the construction of magnificent churches (Rome, Constantinople), donations and grants, exemptions from decurial duties for the clergy, juridical competences for the bishops, and exceptional promotions for Christian officials. Pagans were not persecuted, however, and Constantine retained the title of pontifex maximus. But he spoke of the pagan gods with contempt and forbade certain types of worship, principally nocturnal sacrifices. In 331 he ordered an inventory of pagan property, despoiled the temples of their treasure, and finally destroyed a few Eastern sanctuaries on the pretext of immorality.
The churches were soon to feel the burden of imperial solicitude: the “secular arm” (i.e., the government) was placed at the service of a fluctuating orthodoxy, for the emperor was impressionable to arguments of various coteries and became quite lost in theological subtleties. In 314 the Council of Arles had tried in vain to stop the Donatist schism (a nationalistic heretical movement questioning the worthiness of certain church officials) that arose in Africa after Diocletian’s persecutions. The Arian heresy raised even more difficulties: Arius, an Alexandrian priest and disciple of Lucian of Antioch, questioned the dogma of the Trinity and of the Godhead of Christ, and his asceticism, as well as the sharpness of his dialectics, brought him many followers; he was convicted several times, but the disorders continued. Constantine, solicited by both sides and untroubled by doctrinal nuances that were, moreover, foreign to most believers in the West, wished to institute a universal creed; with this in mind he convened the general Council of Nicaea, or Nicene Council, in 325. He condemned Arius and declared, in spite of the Easterners, that Jesus was “of one substance” with God the Father. Nevertheless, the heresy continued to exist, for Constantine changed his mind several times; he was influenced by Arian or semi-Arian bishops and was even baptized on his deathbed, in 337, by one of them, Eusebius of Nicomedia.