Later Roman Empire

In historiography, the Late or Later Roman Empire, traditionally covering the period from 284 CE to 641 CE, was a time of significant transformation in Roman governance, society, and religion. Diocletian's reforms, including the establishment of the tetrarchy, aimed to address the vastness of the empire and internal instability. The rise of Christianity, legalized by Constantine the Great in 313 CE, profoundly changed the religious landscape, becoming a central force in Roman life. Simultaneously, barbarian invasions, particularly by the Goths and the Huns, weakened the Western Roman Empire, which collapsed in 476 CE. In contrast, the Eastern Roman Empire endured, evolving into the Byzantine Empire and laying the foundations for medieval Europe.

This article ends with the Arab conquest of Egypt in 641 CE and the beginning of the Byzantine Dark Ages.

In comparison with previous periods, studies on Later Roman history are based on diverse but mainly biased written sources. Completed around 314, Lactantius's work about the Diocletianic Persecution, titled On the Death of the Persecutors, is an early example of prejudiced narrative. Hagiographies—Christian martyrs' and ascetics' biographies—form the period's most distinctive literary genre. The Martyrs of Palestine by Eusebius, Bishop of Caesarea, introduced it in the early 4th century, but a later work, the Life of Anthony about the Egyptian hermit, Anthony the Great set a template for further works. Eusebius' Life of Constantine about the first Christian emperor is a useful collection of letters and official documents. In contrast with classical literature, Hagiographic works regularly presented women as leading characters. Examples include the Life of Macrina about a wealthy and pious aristocrat Macrina the Younger.

With his Church History, Eusebius originated another new literary genre with the focus on Christian missionaries, church leaders, martyrs and heretics. This first church history was revised and resumed by Rufinus in 402. Books written by Socrates of Constantinople, Sozomen and Theodoret are the principal sources of ecclesiastic life until the mid-5th century. Orosius was the first scholar to integrate elements of classical and church history in the 420s. With his History against the Pagans, he wanted to demonstrate that recent calamities cannot be regarded as a punishment for the suppression of traditional Roman religion. Only three church historians' works survived from the 6th century: Zacharias Rhetor, John of Ephesus and Evagrius Scholasticus focus on theological debates. Later church histories, primarily destined to demonstrate the effects of divine providence on human life, seldom provide sufficient information for a deeper analysis of secular history. The Chronicon Paschale is of the utmost importance for the study of the otherwise poorly documented early 7th century. A late source, Theophanes the Confessor's 9th-century Chronographia, is invaluable for the military history of the 620s.

Most information about military and political history has been preserved in secular historians' works. When writing of events familiar to them or their acquaintances, they are mostly reliable. Aurelius Victor and an unknown author completed short imperial biographies in the second half of the 4th century, allegedly using a common source. Around 370 two imperial secretaries, Eutropius and Festus, completed concise accounts of Roman history. Pagan Greek officer Ammianus Marcellinus "has a claim to be the finest Latin historian of any period", according to historian Stephen Mitchell, although only fragments of his Histories survived. Likewise only fragments are known from the works of Ammianus' continuator, Sulpicius Alexander. Scholars studying 5th-century Roman history can primarily rely on a 10th-century collection of fragments from earlier Greek authors' works. One of them, Priscus, wrote a detailed report of his visit at Attila the Hun's court in 449. The pagan Zosimus, the sole prominent Later Roman historian whose full work survived, blames Christianity for the quick decline of the Roman Empire. The last outstanding Roman historian, Procopius completed detailed accounts of Emperor Justinian I's rule. His Wars covers military actions. His Buildings provides a list of the achievements of Justinian's building program, but archaeological evidence sometimes contradicts it. He summarizes his true views of Justinian and Justinian's inner circle in the Secret History, describing him as a wicked and unscrupulous figure surrounded by intrigues and scandals. The events of the second half of the 6th century are best known from the fragmentary works of Agathias and Menander the Guardsman. Agathias emphasizes the effect of unexpected events on history, Menander mainly cover diplomacy. The early-7th-century Theophylact Simocatta is the least reliable Later Roman historian: both his chronology and topography are chaotic.

The systematic collection of legal texts commenced in the Late Roman period. The Code of Theodosius contains about 2,500 entries and covers the period between 335 and 437. The Code of Justinian expands the Code of Theodosius with rulings issued by emperors between 437 and 529. Both legal compilations are important sources of state administration, although their actual application is unproven. The early 5th-century Notitia Dignitatum is a useful source of the empire's civil and military administration even if it likely contains exaggerated data: both military commanders and high-ranking civil servants tended to emphasize the importance of their office by giving overestimated numbers to official data collectors. In comparison with the classical age, Late Roman inscriptions are available in lesser quantity. Although collective ovations for dignitaries were still regularly commemorated in public places, in this period they were made mainly in honor of imperial officials instead of local leaders as it had been common in the previous centuries.

Archaeological finds also abound, although "they remain understudied" (as Mitchell emphasizes it in 2015). The systematic study of archaeological evidence intensified after the dating system of Late Roman pottery stabilized.

Looking back from the early 3rd century, the Roman historian Cassius Dio concluded that the Roman Empire had descended "from a kingdom of gold to one of iron and rust" after Emperor Marcus Aurelius' death in 180 AD. Cassius' words obviously reflect the Roman senators' aversion to the Severan emperors, because other written sources and archaeological evidence indicate that the empire recovered during their reign between 193 and 235. As a surviving element of Roman republican traditions, Roman emperors had been in theory no more than principes senatus, or first among the senators during the first centuries of the monarchy. This notion of equality was manifest at the relatively high level of informality in the imperial court. Distance between emperors and Roman citizens increased and the ceremony of prostration was first documented during the Severans' reign. In 212, Emperor Caracalla granted full Roman citizenship to his all free subjects except for the dediticii, that is aliens who had been forced into submission or admitted to the empire.