Two catastrophes ended the Byzantine Empire. The first came from fellow Christians, the second from the rising power of the Ottoman Turks.

The Fourth Crusade

In 1202, a new crusade gathered in Venice, intending to attack Egypt. The crusaders could not pay the Venetians for the ships they had ordered. To work off the debt, they first attacked the Christian city of Zara on the Adriatic for Venice. Then a Byzantine prince, Alexios, son of a deposed emperor, offered them money and help if they would restore his father to the throne in Constantinople. The crusaders, led in practice by the elderly, blind Venetian doge Enrico Dandolo, sailed to Constantinople.

They restored the prince and his father, but the new rulers could not pay what they had promised and were soon overthrown. In April 1204, the crusaders stormed the city. For three days they looted and killed, stripping churches, palaces and tombs. Holy relics, artworks and treasures were carried to the West. The four bronze horses that now stand in St. Mark's Basilica in Venice were taken from the Hippodrome. Pope Innocent III, who had forbidden attacks on Christians, condemned the sack, though he also accepted the new Latin rule in the East as a chance to reunite the churches.

The Latin Empire and the exiles

The crusaders set up a Latin Empire in Constantinople, ruled by Western nobles, while Venice took valuable ports and islands. Byzantine nobles fled and founded successor states, the most important at Nicaea in western Anatolia. In 1261, the Nicaean ruler Michael VIII Palaiologos recaptured Constantinople. But the restored empire was a shadow of its former self: impoverished, surrounded by rivals and divided by civil wars. The memory of 1204 poisoned relations between Orthodox and Catholic Christians for centuries. In 2001, Pope John Paul II apologized for the sack.

The Ottoman rise

In the fourteenth century, a small Turkish state in northwest Anatolia, led by a family descended from a leader named Osman, grew rapidly. The Ottomans crossed into Europe in the 1350s and conquered much of the Balkans. By the early fifteenth century, the Byzantine Empire consisted of little more than Constantinople and a few scattered territories, surrounded by Ottoman lands. Its emperors traveled to the West seeking help. At the Council of Florence in 1439, Byzantine leaders agreed to reunite with the Roman church in exchange for aid, but most Orthodox clergy and people back home rejected the union, and help never came on the scale needed.

The siege of 1453

In 1451, a young and ambitious sultan, Mehmed II, came to the Ottoman throne, determined to take Constantinople. He built a fortress on the Bosporus to cut off supplies from the Black Sea. He hired a Hungarian engineer, Orban, who cast enormous cannons capable of hurling huge stone balls against the ancient walls.

The siege began in April 1453. The emperor, Constantine XI Palaiologos, had perhaps seven or eight thousand defenders, including Genoese soldiers led by Giovanni Giustiniani, against an Ottoman army many times larger. A great chain across the entrance to the Golden Horn kept Ottoman ships out of the harbor, until Mehmed had about seventy ships dragged overland on greased logs behind the Genoese suburb of Galata and launched into the Golden Horn.

The cannons battered the walls for weeks, but the defenders repaired the damage each night. In the early hours of 29 May 1453, the Ottomans launched a final assault. Giustiniani was badly wounded and carried away, and the defense in his sector faltered. Ottoman troops broke through. Constantine XI threw off his imperial regalia and died fighting; his body was never identified with certainty. The city was sacked. Mehmed entered and ordered Hagia Sophia converted into a mosque.

After the fall

Mehmed made Constantinople the Ottoman capital. He repopulated the city, brought in people of many faiths, and allowed the Orthodox Church to continue under a patriarch he appointed. He even took the title of Kayser-i Rum, Caesar of Rome, seeing himself as heir to the Roman emperors. The city, gradually known as Istanbul, became one of the great capitals of the world again. The last Byzantine territories fell within a few years: Mistra in Greece in 1460 and the Empire of Trebizond on the Black Sea in 1461.

Worked example: two sacks compared

Compare the sacks of 1204 and 1453.

• Who attacked. In 1204, Western Christians on a crusade nominally aimed at Muslim Egypt. In 1453, the Ottoman sultan, a Muslim ruler openly seeking to conquer the city.
• What followed. In 1204, a weak Latin Empire that lasted fifty-seven years and drained the city. In 1453, a powerful new empire that made the city its capital and rebuilt it.
• Memory. For Orthodox Christians, 1204 was a betrayal by fellow Christians; some later said they preferred the sultan's turban to the cardinal's hat. For Greeks, 1453 became a national tragedy; for Turks, a great victory.

The comparison shows that religious labels alone do not predict how people treat each other, and that the same event can carry very different meanings for different communities. Understanding a conflict requires listening to how each side remembers it.