Abdication, 305 A. D. On 1 May, 305 A. D., Diocletian and Maximian, after a joint rule of twenty years, formally abdicated their authority and retired into private life. Diocletian withdrew to his palace near Salona in Dalmatia, and Maximian, much against his will, to an estate in Lucania. Galerius and Constantius succeeded them as Augusti.
II. Constantine I, the Great: 306–337 a. d.
Constantine Caesar, 306 A. D. Diocletian’s plan for securing an orderly succession of rulers for the empire had neglected to take into account individual ambitions and the strength of dynastic loyalty among the soldiers. Its failure was forecast in the appointment of the new Caesars. Galerius, who was the more influential of the new Augusti, disregarded the claims of Constantine, the son of Constantius, and nominated two of his own favorites, Severus and Maximinus Daia. In this Constantius acquiesced but when he died in Britain in 306 A. D., his army acclaimed Constantine as his successor. Galerius was forced to acknowledge him as Caesar.
The revolt of Maxentius, 306 A. D. In the same year Maxentius, the son of Maximian, took advantage of the opposition aroused in Rome by the attempt of Galerius to make the city subject to taxation, and caused himself to be proclaimed Caesar. He was supported by his father, who emerged from his enforced retirement, and defeated and brought about the death of Severus, whom Galerius had made Augustus, and sent to subdue him. Maxentius then took the title of Augustus for himself. The same rank was accorded to Constantine by Maximian, who made an alliance with him and gave him his daughter, Fausta, in marriage. Upon the failure of an attempt by Galerius to overthrow Maxentius, an appeal was made to Diocletian to return to power and put an end to the rivalries of his successors (307 A. D.). He refused to do so, but induced Maximian, who had quarrelled with his son, to withdraw a second time from public life. Licinius, who had been made Caesar by Galerius in place of Severus, became an Augustus, while Daia and Constantine each received the title of Son of Augustus (filius Augusti), a distinction which Constantine, from the beginning, and Daia, soon after[pg 322]wards, ignored. Thus, by 310 A. D., there were five Augusti (including Maxentius), in the empire and no Caesars. It was not long before the ambitions of the rival emperors led to a renewal of civil war.
The rival Augusti, 310–312 A. D. In 310 Maximian tried to win over the army of Constantine, but his attempt failed and cost him his life. The following year Galerius died, after having, in concert with Constantine and Licinius, issued an edict which put an end to the persecution of the Christians and granted them the right to practice their religion; an admission that the state had failed in its plan to stamp out the religion of Christ. The empire was then divided as follows: Constantine held Britain, Gaul and Raetia, Maxentius Spain, Italy and Africa, Licinius the Illyrian and Balkan provinces, and Maximinus Daia the lands to the east of the Aegean, including Egypt. The attempt of Maxentius to add Raetia to his dominions brought him into conflict with Constantine. Constantine allied himself with Licinius, and Maxentius found a supporter in Maximinus. Without delay Constantine invaded Italy, and routed the troops of Maxentius at Verona. He then pressed on to Rome and won a final victory not far from the Milvian bridge (312 A. D.). Maxentius perished in the rout. It was in this campaign, as a result of a vision, that Constantine adopted as his standard the labarum, a cross combined with the Christian monogram formed of the first two letters of the Greek word Christos (Christ).
Constantine and Licinius, 313–324 A. D. In 313 Constantine and Licinius met at Milan, where they issued a joint edict of toleration, which placed Christianity upon an equal footing with the pagan cults of the state. Although this edict enunciated the principle of religious toleration for the empire, it was issued with a view to win the political support of the Christians and pointed unmistakably to Christianity as the future state religion. Shortly after the publication of the Edict of Milan, Maximinus Daia crossed the Bosphorus and invaded the territory of Licinius. He was defeated by the latter, who followed up his advantage and occupied Asia Minor. Upon the death of Maximinus, which followed within a short time, Licinius fell heir to the remaining eastern provinces. These now received the religious toleration previously extended to the rest of the empire.
However, the concord between the surviving Augusti was soon broken by the ambitions of Constantine, who felt aggrieved since Licinius controlled a larger share of the empire than himself. A brief war ensued, which was terminated by an agreement whereby [pg 323]Licinius ceded to Constantine the dioceses of Moesia and Pannonia (314 A. D.). In 317 they jointly nominated as Caesars and their successors, Crispus and Constantine, the younger sons of Constantine, and Licinianus, the son of Licinius. However, although they continued to act in harmony for some years longer, it was evident that they still regarded one another with jealous suspicion. This came clearly to light in the difference of their policies towards the Christians. The more Constantine courted their support by granting them special privileges, the more Licinius tended to regard them with disfavor and restrict their religious liberty. Finally, in 322 A. D., when repelling a Gothic inroad, Constantine led his forces into the territory of Licinius, who treated the trespass as an act of war. Constantine won a signal victory at Adrianople and his son Crispus destroyed the fleet of Licinius at the Hellespont. These disasters induced Licinius to withdraw to Asia Minor. There he was completely defeated by Constantine near Chrysopolis (18 September, 324 A. D.). Licinius surrendered upon assurance of his life, but the following year he was executed on a charge of treason. Constantine was now sole emperor.
Constantine sole emperor, 324–337 A. D. Constantine’s administrative policy followed in the steps of Diocletian, whose organization he elaborated and perfected in many respects. The praetorian prefecture was deprived of its military authority, which was conferred upon the newly-created military offices of master of the horse and the foot (magister equitum and peditum). This completed the separation between the military and civil offices. Diocletian’s field force was strengthened by the creation of new mobile units, and his efficient army enabled Constantine to defend the empire against all barbarian attacks. Upon waste lands within the frontiers he settled Sarmatians and Vandals, while he greatly increased the barbarian element in the army as a whole, but particularly among the officers of higher rank.
Constantinople, 330 A. D. Of special importance for the future history of the empire was the founding of a new capital, called Constantinople, on the site of ancient Byzantium. After four years’ preparation, the new city was formally dedicated on 11 May, 330 A. D. The choice of the site of the new capital of the empire was determined by its strategic importance. It was conveniently situated with respect to the eastern and Danubian frontiers, and well adapted as a link between the European and Asiatic parts of the empire. The aim of the emperor was to make Constantinople a new Rome, and he gave [pg 324]it the organization and the institutions of Rome on the Tiber. A new Senate was established there; likewise the public festivals and free bread for the populace. For the latter purpose the grain of Egypt was diverted from Rome to Constantinople.