Origins
The Roman Emperor Constantine moved the imperial capital from Rome to the small Greek city of Byzantion, on the European side of the Bosphorus, in May 330 AD. He renamed the city Constantinople (literally “City of Constantine”) and rebuilt it on a grand scale as a New Rome. The move was both a recognition of the increasing economic and military importance of the eastern provinces and a strategic decision: Constantinople sat at the only land route between Asia and Europe and at the maritime chokepoint between the Black Sea and the Mediterranean.
The Roman Empire was administratively divided into eastern and western halves by Theodosius I in 395 AD. The western half collapsed by stages over the following century, conventionally dated to the deposition of Romulus Augustulus in 476 AD. The eastern half, governed from Constantinople, did not collapse. It continued, with substantial reductions in territory but no breaks in administrative continuity, until 1453. The modern term Byzantine Empire is a 16th-century coinage; the Byzantines themselves consistently called themselves Romaioi — Romans — and their state Romania — Rome.
The Justinianic peak
The Byzantine Empire reached its greatest territorial extent under Justinian I (reigned 527–565). Justinian and his generals Belisarius and Narses reconquered substantial portions of the former western Roman Empire — North Africa from the Vandals (533–534), Italy from the Ostrogoths (535–554), and parts of southern Spain from the Visigoths (552). At Justinian’s death in 565, the Byzantine Empire encompassed the eastern Mediterranean, the Black Sea, the Balkans, North Africa, Italy, and parts of Iberia.
Justinian’s other accomplishments were: the codification of Roman law (the Corpus Juris Civilis of 529–534), which would become the foundation of all European civil-law traditions; the construction of the Hagia Sophia (532–537), the largest enclosed space in the world for nearly a thousand years; and the disastrous Plague of Justinian (541–549), the first recorded pandemic of Yersinia pestis, which killed approximately one quarter of the population of the eastern Mediterranean and weakened the empire’s military and economic capacity for generations.
The western reconquests proved unsustainable. Italy was largely lost to the Lombards within fifteen years of Justinian’s death; Spain was lost to the Visigoths in 624; North Africa was lost to the Arab conquests in 698. The empire’s seventh-century territorial losses to the Arab Caliphate were catastrophic — Egypt, Syria, Palestine, and North Africa were all lost between 634 and 698 — and reduced the empire to roughly Anatolia and Greece, the core territories it would hold for the next several centuries.
The middle Byzantine period
The period from approximately 750 to 1200 was the most intellectually productive of Byzantine history. The Iconoclastic Controversy (726–842) — the dispute over whether religious images were permissible in Christian worship — produced the longest sustained theological debate of the medieval period and ended in the affirmation of Orthodox icon veneration. The Macedonian dynasty (867–1056) presided over a substantial military recovery, the Christianization of the Bulgars and the Rus’ (the conversion of Vladimir of Kiev to Byzantine Orthodoxy in 988 created the eastern Slavic Orthodox world that survives to the present), and the most important Greek classical-revival in medieval scholarship.
The Byzantine intellectual tradition preserved Greek learning that had been lost almost entirely in the Latin West. Most of what survives of Greek philosophy, mathematics, astronomy, and medicine — including the work of Hypatia, of Hipparchus and Ptolemy, of Archimedes, of Plato, Aristotle, and the Hellenistic schools — survived through Byzantine copyists. The 9th-century scholar-patriarch Photius produced the Bibliotheca, the largest single classical-bibliographic survey of late antiquity. The 11th-century scholar Michael Psellos restored Platonic philosophy to the Byzantine intellectual mainstream.
The Crusader catastrophe
The Byzantine Empire’s relations with the Latin West deteriorated through the 11th and 12th centuries. The Great Schism of 1054 formally divided the Catholic and Orthodox churches. The First Crusade (1096–1099) had been originally requested by the Byzantine emperor Alexios I Komnenos as Western mercenary support; the actual Crusader armies were uncontrollable, established their own independent Crusader states in territories the Byzantines had hoped to reincorporate, and were openly hostile to the Byzantines they had come to assist.
The Fourth Crusade (1202–1204) was the catastrophe. The Crusader army, diverted from Egypt by Venetian financial pressure, sacked Constantinople in April 1204. The city was systematically looted for three days; the imperial collections, libraries, and treasury were dispersed; the Empire itself was dismembered into a series of Latin Crusader states. The Byzantine government in exile, the Empire of Nicaea, eventually recovered Constantinople in 1261, but the Byzantine state that emerged from the 1261 reconquest was a small, fragile remnant of its pre-1204 self.
Fall
The Palaiologan dynasty (1259–1453) governed the diminished post-1204 Byzantine state through two centuries of progressive territorial loss. The empire lost most of its Anatolian territories to the Ottoman Turks through the 14th century. By 1450 the Byzantine state consisted of little more than the city of Constantinople and a small enclave in the Peloponnese.
The Ottoman Sultan Mehmed II besieged Constantinople in April 1453 with an army of approximately 80,000 and the largest siege artillery train in history to that date, including the great Hungarian cannon Orban (the second-largest siege gun ever built; the bronze barrel was 27 feet long and could fire a stone ball weighing 600 pounds). The siege lasted 53 days. The walls of Constantinople, which had repelled every previous siege since 717, were breached on the night of 28–29 May 1453.
The last Byzantine emperor, Constantine XI Palaiologos, died fighting at the Theodosian Walls on the morning of 29 May. His body was never identified. He had reigned for four years and three months.
Legacy
The fall of Constantinople in 1453 ended the Roman political tradition that had begun a continuous line of governance in 27 BC. It also produced an immediate intellectual diaspora: Byzantine scholars who had been preserving Greek classical learning fled to Italy and gave the Italian Renaissance its primary access to ancient Greek texts. The 15th-century rediscovery of Plato, Plutarch, and Ptolemy in Western Europe was substantially the work of refugee Byzantines.
The Orthodox religious tradition continued, with Moscow declaring itself the Third Rome by the late 15th century, the institutional and theological successor to fallen Constantinople. The Ottoman Empire, which had inherited the Byzantine capital and many of its administrative practices, ruled the Byzantine territorial core until 1922.
Modern Istanbul — the largest city in Turkey, with approximately 16 million inhabitants — sits on the same site as Byzantion, Constantinople, and the Ottoman capital. The walls Constantine built, the Hagia Sophia Justinian commissioned, and the city plan the Theodosian dynasty established remain visible in the modern city.