Byzantine History: The Eastern Roman Empire to 1453

Constantinople became an imperial capital in 330. Its emperors continued Roman government after the western court disappeared in 476. Justinian recovered North Africa and much of Italy, but seventh-century conquests removed Syria and Egypt. Later rulers regained territory before the Fourth Crusade divided the empire in 1204. The Ottomans captured Constantinople in 1453, ending its imperial government. Roman law remained central to the state’s administration throughout these changes.

The rulers and inhabitants called themselves Romans; “Byzantine” is a later historical designation. Constantinople governed a predominantly Greek-speaking state, especially after the seventh century. Its territory changed repeatedly between Mediterranean expansion and concentration around the capital and nearby regions.

On this page8 sections

From late Roman government to an eastern empire

Diocletian responded to civil war and frontier pressure by sharing imperial responsibilities. In 293, the tetrarchy combined two senior emperors, the Augusti, with two junior Caesares. Separate courts governed different regions. Constantine later defeated rival claimants and re-established rule by one emperor.

Constantine I replaced the tetrarchic succession with a dynastic system and made the eastern city of Byzantium, refounded as Constantinople in 330, a major imperial capital. Its position between Europe and Asia, close to the Danube and the eastern frontier, made it useful for controlling communications, trade and military movements. Constantine also strengthened the currency, reorganised the army and separated civil administration from military command in the regions. The gold solidus became a stable currency, while new fortified walls and administrative centres helped the government manage the empire’s resources.

Constantine granted patronage to Christianity and supported church councils, including Nicaea in 325. Bishops acquired judicial and administrative responsibilities. Theodosius I promoted Nicene Christianity as the imperial religious standard. Subsequent doctrinal disputes repeatedly involved emperors and local churches.

Theodosius I’s sons Arcadius and Honorius took the eastern and western courts in 395. The East retained important urban centres and revenues that supported armies and fortifications. Western rule fragmented during the fifth century, and Romulus Augustulus was deposed in 476. The eastern emperor continued to claim Roman imperial authority.

Justinian and the limits of imperial restoration

The eastern government did not regard the disappearance of the western court as the end of Roman imperial authority. Under Justinian I, who ruled from 527 to 565, it attempted to recover former Roman territories. An agreement with Khosrau I, king of the Persian Sasanian dynasty, temporarily secured the eastern frontier, allowing resources to be used in the west. General Belisarius conquered the Vandal kingdom in North Africa beginning in 533, and Byzantine armies then fought a long war against the Ostrogoths in Italy. The empire also gained a foothold in southern Spain and retained territory around the western Mediterranean.

These conquests restored a wide imperial map, but they were expensive to hold. The Italian war lasted for years, local resistance continued in North Africa, and the Balkans faced incursions from Slavic groups and others. Imperial forces had to defend several distant regions at once. Justinian’s government also confronted the Nika revolt in Constantinople in 532, an urban uprising that was violently suppressed.

Justinian’s reign also shaped the empire through law and religious policy. Commissions organised Roman legal materials into the Corpus Juris Civilis, including the Code, the Pandects, the Institutes and later imperial enactments. The collection gave later governments a structured body of Roman law. At the same time, Justinian intervened in conflicts among Christian communities, including disputes involving Chalcedonian and non-Chalcedonian positions.

The sixth century ended with serious pressures. Epidemics damaged population and economic activity, warfare consumed revenue, and the Lombards occupied much of Italy after Justinian’s death. Maurice achieved military successes and stabilised parts of the Danube frontier, but his overthrow and murder in 602 led to a long war with the Sasanian Empire. The conflict exhausted both powers and left them vulnerable to a new expansion from Arabia.

The seventh-century crisis and a smaller Roman state

Heraclius became emperor in 610 during the war with the Sasanians. Persian forces subsequently captured Damascus and Jerusalem, taking the True Cross from Jerusalem in 614. Heraclius counterattacked and defeated a Sasanian army near Nineveh in 627. The ensuing settlement restored territories, although prolonged warfare had depleted both states.

Arab armies conquered Syria and Palestine, and Egypt fell by 642. Loss of those provinces removed major revenues and the Egyptian grain supply for Constantinople. Raids reached Anatolia and attacks threatened the capital, where fortifications and the incendiary weapon known as Greek fire helped its defence.

The empire’s political geography changed along with its military needs. The old urban culture declined as towns shrank, relocated to defensible sites or became partly ruralised. Constantinople itself lost much of its population and no longer received free grain from Egypt. In Asia Minor, the government developed the theme system, in which military districts were connected with civil administration and troops answered to the imperial government. The exact stages of this development were gradual, but its effect was to link defence, taxation and provincial government more closely.

The Balkans also changed. The movement of imperial troops to the eastern fronts weakened Roman control north of the mountains and the Danube. Slavic communities expanded southward, while Bulgars established a state south of the Danube after defeating Byzantine forces in 680. A treaty recognised Bulgarian power over territories previously linked to Constantinople. The empire continued to campaign in the Balkans, but its authority there was no longer the direct and comprehensive rule of the late Roman period.

Religious conflict added to the political strain. Heraclius promoted monotheletism, a proposed compromise in the dispute over Christ’s will, but it failed to reconcile the opposing Christian positions. Later emperors and church leaders also disputed the status of religious images. The first period of official iconoclasm, meaning opposition to the veneration of icons, began under Leo III in the eighth century. The policy provoked resistance from supporters of icons and was reversed at the Second Council of Nicaea in 787. A second period of iconoclasm lasted from 813 to 843, after which the public veneration of icons was restored.

The remaining state concentrated on Constantinople and Anatolia. Greek increasingly replaced Latin in official administration. The emperor retained Roman political claims and legal institutions within a smaller territorial base.

Recovery under the Macedonian emperors

From the late ninth through the eleventh centuries, the empire recovered territory, population and wealth. The Macedonian emperors benefited from more stable administration, the reduced intensity of internal religious conflict and the effectiveness of the theme-based military system. Government policy often protected smaller agricultural landholders against the expansion of aristocratic estates. Since these landholders were connected to military service and taxation, their preservation supported both the army and the fiscal base of the state.

Byzantine armies moved onto the offensive in the east. They recovered territory from Muslim rulers in northern Syria and Mesopotamia, while Byzantine control was strengthened in Cyprus and southern Italy. The empire also defeated the Bulgarians after a prolonged struggle. Basil II’s campaigns ended with the incorporation of Bulgaria into the empire by 1018 and restored a Danube frontier that had not been held since the time of Heraclius.

Muslim armies conquered Sicily between 827 and 902, while Byzantium retained parts of southern Italy. Relations with the Rus combined war, trade and religious missions. Conversion to Orthodox Christianity connected Rus rulers with Constantinople, and soldiers from the north served in imperial forces, including the Varangian Guard.

Agricultural production and settlement expanded in many regions during the middle Byzantine recovery. Constantinople’s workshops and merchants supplied silk and metalwork to wider markets. Scholars recopied Greek texts, while patrons funded churches and religious art.

Campaigns strengthened some provincial military families, and large landowners accumulated estates. Professional soldiers and foreign contingents supplied an increasing share of imperial forces. After Basil II’s death in 1025, contested successions and court rivalries placed pressure on government and military finance.

Manzikert and the Komnenian restoration

Norman conquest ended Byzantine rule at Bari in 1071. In the same year, Alp Arslan defeated and captured Romanos IV Diogenes at Manzikert. Subsequent civil war weakened resistance to Turkish settlement in Anatolia. By Alexios I’s accession in 1081, the empire had lost control of much of the interior.

Alexios I Komnenos seized power in 1081 during this crisis. He faced Seljuk forces in the east, Normans in the west and Pecheneg attacks in the Balkans. His government restored parts of the military system, negotiated when necessary and used diplomacy to exploit rivalries among neighbouring powers. The defeat of the Pechenegs at Levounion in 1091 removed one immediate Balkan danger. Alexios also recovered a number of cities and islands in western Asia Minor, although he lacked the resources to reconquer the whole plateau.

The First Crusade brought new opportunities and new dangers. Alexios had asked the western church and rulers for military assistance, but the large armies that arrived were not simply the mercenaries he had expected. Byzantine officials supplied guides and sought oaths that territories taken from the Turks would be returned to the empire. The crusaders helped recover some places, but disputes over Antioch and other conquests produced lasting mistrust between Constantinople and the Latin states.

Under John II and Manuel I Komnenos, the empire enjoyed a partial restoration from the early twelfth century. Byzantine power was extended in parts of Anatolia and the Balkans, and imperial influence was maintained over Antioch and other crusader territories. Constantinople prospered through trade with Venetian, Genoese and other Italian merchants. The same commercial links increased western influence inside the empire and gave Italian powers privileges that later weakened Byzantine control of maritime trade.

The Komnenian recovery depended on active emperors, military expenditure and careful diplomacy, so it remained vulnerable to succession disputes and aristocratic rivalry. After Manuel’s death in 1180, political violence and contested rule weakened the government. The Angeloi dynasty struggled to control provincial forces, finance defence and manage relations with the crusaders. Rebellions in the Balkans helped create the Second Bulgarian Empire, while the Normans attacked Byzantine territory in Greece.

1204 and the Byzantine successor states

The Fourth Crusade transformed the political map. Originally directed toward Egypt, the expedition became entangled in Venetian financial demands and Byzantine dynastic politics. Crusaders intervened in Constantinople, restored Isaac II and his son Alexios IV for a time, and then attacked the city when promised payments could not be made. On 13 April 1204, the crusaders captured Constantinople. The city was plundered for three days, and the victors divided Byzantine lands between the Latin Empire, Venetian interests and other western leaders.

A Latin emperor ruled Constantinople after 1204. Byzantine rulers established competing centres at Nicaea, Epirus and Trebizond. Each sought territory and legitimacy while confronting Latin and neighbouring powers. The sack also removed wealth, relics and resources from the capital.

Nicaea rebuilt an imperial administration and expanded against Latin-held territories. Michael VIII Palaiologos regained Constantinople in 1261. His government diverted resources towards European campaigns and pursued church union with Rome to seek western support. These measures provoked resistance and placed pressure on Anatolian districts.

Fragmentation and the Ottoman advance

The restored empire never recovered the territorial or financial strength it had possessed before 1204. The Palaiologan rulers controlled Constantinople and a shifting collection of territories in Greece, the Balkans and Anatolia, but rival states and foreign powers held much of the former imperial world. The decline of Seljuk authority after the Mongol invasion of Anatolia allowed Turkish principalities to emerge. One of these, founded by Osman, developed into the Ottoman Empire.

Internal conflict made the situation worse. Civil wars in 1321 to 1328 and 1341 to 1347 divided the government and allowed the Ottomans to gain ground in Anatolia. The second conflict also encouraged the use of Turkish mercenaries. In 1354, these forces seized Gallipoli after an earthquake had damaged its fortifications, giving the Ottomans a permanent base in Europe. Serbian expansion under Stefan Dušan further reduced Byzantine territory in Macedonia, Thessaly and Epirus, although Serbian power later fragmented.

By the fifteenth century, the empire was largely confined to Constantinople, parts of the Peloponnese and a few scattered possessions. The Ottoman conquest of the Balkans surrounded the capital. Byzantine emperors repeatedly appealed to western powers, but proposed military assistance was often tied to submission of the Eastern Church to Rome. Church union could be proclaimed by emperors, yet it was deeply unpopular among many Orthodox clergy and inhabitants, limiting its political usefulness.

The fall of Constantinople in 1453

Mehmed II’s army besieged Constantinople in April 1453. Estimates commonly place the attackers around 80,000 and the defenders around 7,000, including foreign troops. Ottoman artillery damaged the walls, while the defenders struggled to cover the city’s long perimeter.

Ottoman forces entered Constantinople on 29 May 1453. Constantine XI died during the final defence. The Morea remained under Byzantine rulers until 1460, and Trebizond surrendered in 1461.

The fall of the capital did not immediately end every Byzantine-ruled territory. Mystras, with its palace complex, churches and houses, remained the seat of the Morea until its surrender to the Ottomans in 1460. Its remains belong to a late Byzantine provincial centre whose political history continued beyond 1453.