The Byzantine Empire was the eastern half of the Roman Empire, ruled from Constantinople (modern Istanbul) from 330, when Constantine made the city his capital, until the Ottoman conquest in 1453. Its emperors governed a state whose people called themselves Romans and wrote mostly in Greek. It reached its greatest extent under Justinian I (r. 527–565); estimates of its peak area run from 2.7 million km² around 555 to 2.8 million km² for around 450, and Justinian’s empire stretched from Italy and the western Mediterranean coast to the Balkans, Anatolia, Syria and Egypt, and as many as 27 million people lived in it around 540. It mattered because it carried Roman law, Greek learning and Orthodox Christianity through the Middle Ages, and because Constantinople remained the largest and wealthiest city in Europe until the 13th century. How do historians know where its borders ran, how many people it held and what it traded? From a handful of very different kinds of evidence, each with its own blind spots.
Procopius and Hierocles: Justinian’s Empire on Paper
For the empire at its peak, the main narrative source is Procopius of Caesarea (c. 500–565). He served on the staff of the general Belisarius, saw the Nika riots of January 532, joined the expedition that took Carthage from the Vandals in 533, and lived through the Gothic siege of Rome that ended in March 538. His History of the Wars, in eight books brought up to 553, is the backbone of what is known about Justinian’s reconquests in North Africa and Italy. His Buildings praises the emperor’s fortifications and churches across the provinces, which makes it a gazetteer of places Justinian wanted to be seen protecting. His Secret History, probably written around 550 and only rediscovered in the Vatican Library in 1623, attacks the same rulers he praised elsewhere. Read together, the three show why historians treat any single Byzantine author with caution.
A drier document gives the administrative map. The Synecdemus, attributed to Hierocles and dated to Justinian’s reign before 535, lists 912 cities divided among 64 provinces, or eparchies. It is essentially a register, and that is its value: it records which towns the government counted, province by province, early in Justinian’s reign. Four centuries later it was one of the main sources for Constantine VII’s own book on the provinces, De Thematibus.
The Madaba Map: A 6th-Century Mosaic of the Holy Land
Some geography survives as a picture. In the floor of the Byzantine church of Saint George in Madaba, Jordan, a mosaic maps the land from Lebanon to the Nile Delta and from the Mediterranean to the Eastern Desert. It is the oldest surviving original map of the Holy Land and of Jerusalem. Its date comes from what it shows and what it leaves out: it includes the New Church of the Theotokos in Jerusalem, dedicated on 20 November 542, but no Jerusalem buildings put up after 570, so it was laid between those years. The mosaic also records later history in its damage. Madaba fell to the Sasanian Persians in 614, figural motifs were removed under the Umayyad Caliphate in the 8th century, and an earthquake largely destroyed the town in 746. Remnants turned up in 1884 and 1886 while a new Greek Orthodox church was being prepared on the site, but the full map was only noticed in October 1896, during clearing work for the new church’s floor.
De Administrando Imperio: An Emperor’s Guide to the Neighbours
The best view of the empire’s frontiers in the 10th century comes from an emperor writing to his son. Constantine VII (sole ruler 945–959) compiled De Administrando Imperio as a policy manual for Romanos II, probably between about 948 and 952. It describes the peoples around the empire, including the Hungarians, Pechenegs, Kievan Rus’, Serbs, Croats, Arabs, Lombards, Armenians and Georgians, how each came to occupy its land, and how Constantinople should deal with them. Chapters 1–8 set out imperial policy toward the Pechenegs and the advantages of keeping peace with them, and chapters 49–52 give practical guidance on taxing new provinces and running the navy. Much of the book mixes legend with fact, but it shows how the court in Constantinople understood the map around it.
The imperial family also wrote history. Anna Komnene (1083–1153), daughter of Emperor Alexios I Komnenos, wrote the Alexiad, an account of her father’s reign that is the most important primary source for Byzantine history in the late 11th and early 12th centuries and for the arrival of the First Crusade. It is a daughter’s defence of her father, written by a princess who had herself tried to depose her brother John II in favour of her husband, so historians read its account of the Crusaders alongside the Latin chronicles written by the Crusaders themselves.
Liutprand of Cremona and Benjamin of Tudela: Outsiders in Constantinople
Foreign visitors recorded what insiders took for granted. Liutprand of Cremona (c. 920–972) went to Constantinople on a goodwill mission in 949 and may even have supplied material for chapter 26 of Constantine VII’s book. He returned in 968 to ask Nikephoros II Phokas for a Byzantine princess as a bride for the future Otto II. His Relatio de Legatione Constantinopolitana is an important source for the 10th-century court, and openly hostile: when officials confiscated the purple silks he had bought, he retorted that at home prostitutes and conjurers wore purple. Its value lies partly in the bias, which shows how the Latin West saw the empire it called “Greek”.
Benjamin of Tudela, a Jewish traveller from Navarre, passed through Constantinople on a journey of about 1165–1173 that took him on to Baghdad, Persia and Egypt. He counted the Jewish communities in each town he visited and described occupations and trade, making his itinerary a source for the empire’s cities in the Komnenian period. Nearly two centuries later the Moroccan traveller Ibn Battuta reached the city in late 1332 or 1334, met Emperor Andronikos III Palaiologos and visited Hagia Sophia. By then the state was a shadow of Justinian’s: the population had fallen to about 2 million by 1312.
Gold Solidi and 40,000 Lead Seals
Coins carry information no chronicler bothered to write down. Constantine the Great struck the gold solidus, or nomisma, at 72 to the Roman pound, about 4.5 g of nearly pure gold, and the empire kept that standard for some 700 years. Its fineness is therefore a direct measure of state finances. Under Michael IV (1034–1041) debasement began, and it sped up after the defeat at Manzikert in 1071, until under Nikephoros III (1078–1081) the coin held only about a third gold. Alexios I replaced it in 1092 with the hyperpyron, about 85 percent gold.
Lead seals fill gaps left by lost archives. Officials closed letters and documents with stamped lead discs naming the sender and his office, and more than 40,000 survive, far more than the documents they once sealed. The study of them, sigillography, lets historians trace who held which post in which province and when, and the first international colloquium devoted to Byzantine seals met at Dumbarton Oaks in 1986. A seal of Michael Keroularios, patriarch from 1043 to 1059, survives from the churchman whose disputes with Pope Leo IX played a role in the events that led to the schism of 1054.
Yenikapı and Yassı Ada: What the Shipwrecks Add
Trade is where archaeology says most. In 2004 excavations at Yenikapı in Istanbul uncovered the Harbour of Theodosius, Constantinople’s commercial port from the 5th to the 10th century, an alternative to the older berths on the Golden Horn. Excavators found 34 sunken ships dating from the 7th to the 11th century, one of the largest such finds in Europe. The hulls record a change in shipbuilding: by around 900 builders had replaced unpegged mortise-and-tenon joints with coaks, and the round cargo ships are flat-floored with inline framing, a break from the classical wine-glass hull. The ships have been conserved at Istanbul University and the Institute of Nautical Archaeology in Bodrum.
Off Yassı Ada, a tiny island near Bodrum on the Turkish coast, the archaeologist George Bass excavated a 4th-century Byzantine wreck and a 7th-century one. The 7th-century ship, published by Bass and Frederick van Doorninck in 1982, is a rare close look at a merchant vessel from the century in which the empire lost Syria and Egypt to the Arab conquests, a period when, despite the losses, trade continued.
Plague DNA and Population Estimates from 27 Million to 50,000
The newest evidence comes from laboratories. Writers such as Procopius described the plague that began around 541, but its cause was only confirmed in 2013, when DNA of Yersinia pestis, the bacterium behind the later Black Death, was recovered from skeletons of victims buried in 6th-century graves in Germany. Comparison with living strains points east: the most basal modern relatives of the 6th-century strain are found in the Tian Shan mountains of Central Asia. Population estimates built from all these sources are rough: as many as 27 million people around 540, about 12 million by 800 after plague and the Arab conquests, perhaps 18 million around 1025, near the end of the Macedonian dynasty, and about 2 million by 1312. When the Ottomans took Constantinople in 1453, only about 50,000 people lived in the city, a tenth of its peak.
No single source tells the whole story, and each must be checked against the others: the chronicles for events, the registers and manuals for the administrative map, the travellers for daily life, and coins, seals, wrecks and bones for what nobody wrote down. Much of the physical city still stands, from the walls to Hagia Sophia; the empire’s story picks up from the Roman Empire before it and continues in the Ottoman Empire that replaced it.