The later Roman Empire

The later Roman Empire (also known as the Dominate, from dominus, “lord”) emerged with the reign of Diocletian in 284, after the great third- century crisis (235-84). Although Diocletian’s attitude was in some sense conservative, he broke away from the republican tradition; he destroyed the institutional facade of the Principate, becoming the founder of a new political order.

During the later Roman Empire, political institutions of the city of Rome lost political leadership. Diocletian lived mainly in Nicomedia, the metro­polis of Bithynia (in Asia Minor), which was made the capital of the eastern part of the empire in 286. After becoming the sole ruler of both the West and the East, in 330 Constantine established Constantinople (ancient Byzantium) as the capital of the empire: the New Rome. Western emperors lived in different cities (Treves, Milan, and Ravenna). Beginning with Emperor Constantius II, there were two imperial senates: one at Rome and one at Constantinople.

The later Roman Empire also witnessed the geographic division of power among several emperors to make it more effective and prevent problems of succession.

The imperial administration rested on an enormous, well-organized, and hierarchical bureaucracy entirely disconnected from the military command. The distinction between public (or senatorial) and imperial provinces dis­appeared completely. At the top of this administrative structure were four praefecti praetorio, two for the West and two for the East. These were the chiefs of the four administrative prefectures into which Diocletian divided the empire: the two Eastern prefectures, Oriens (Egypt and the provinces of Asia and Thrace) and Illyricum (Macedonia and Dacia), and the two Western prefectures of Italy (including Africa) and Gaul (including Spain and Britain). The prefectures were divided into dioceses governed by vicars, and these into provinces governed by presidents (praesides).

The Christianization of the empire occurred during the later Roman Empire. The Edict of Toleration by Emperor Galerius, issued in Serdica (now Sofia) in 311, attempted to put an end to the official persecution of Christians throughout the empire. Very controversial is the so-called Edict of Milan (313), issued by emperors Constantine and Licinius. The term Edict of Milan is a modern construct used to describe a document preserved in divergent forms by two contemporaries of Emperor Constantine: Lactantius (De mortibus persecutorum 48.2-12) and Eusebius of Caesarea (Historia Ecclesiastica 10.5.2-14). The original intent of the document, its nature, and its provenance are still contentious questions. The Edict of Milan seems to have been the out­come of a political agreement concluded in Milan between Constantine and Licinius in early February 313, with the aim of granting liberty of worship to all religions, including Christianity, and the restoration of properties con­fiscated from Christians during the persecutions beginning in 303.

On February 27, 380, Emperors Theodosius, Gratian, and Valentinian II issued the imperial constitution Cunctos populos, also known as the Edict of Thessalonica (C.Th. 16.1.2). This edict marked the end of a great fourth­century religious controversy by declaring Nicene Trinitarian Christianity to be the only established imperial religion and the only one that could be called Catholic as such.

On the death of Emperor Theodosius in 395, the empire was formally divided into two parts. Theodosius left the East to his son Arcadius, who was about eighteen years old, and the West to his son Honorius, who was about ten. This partition of the mainly Greek-speaking East from the Latin West was to have far-reaching repercussions in later centuries. The Roman Empire was never reunited, and the destinies of the two halves of the empire were vastly different. Great hordes of Germans invaded the Western Empire. In 410 the Goths sacked Rome, and in 476 the last Western emperor, Romulus Augustulus, was deposed by the Germanic Odoacer, who became the first king of Italy. In the Eastern Empire, the conception of a Roman Empire embracing the whole Mediterranean area, both eastern and western, endured until the death of Emperor Justinian, in 565. The Eastern Empire persisted through Late Antiquity and the Middle Ages in the form of the Byzantine Empire, until it fell to the Ottoman Turks in 1453 at the beginning of the modern era.