The crusade had been raised to attack Muslim-held Egypt, but debts to Venice and an alliance with a Byzantine pretender diverted it to Constantinople. After breaching the sea walls on April 12, the crusaders sacked the city, looting churches, killing civilians and destroying works of art, including ancient bronze statues melted down for coin. Venice took the four bronze horses that now stand at St Mark's Basilica. The crusaders set up a Latin Empire, and Byzantium never fully recovered.
The Fourth Crusade was undone by its finances. Its leaders had contracted Venice to build a fleet for some 33,500 men, but only about a third that number arrived, and they could not pay. The aged, nearly blind Venetian doge Enrico Dandolo offered a deal: the crusaders would first capture the Christian city of Zara for Venice. Then a Byzantine prince, Alexios Angelos, promised enormous rewards if they restored his deposed father to the throne in Constantinople.
They did so in 1203, but the promised money never came, and the new emperors were overthrown. Early in 1204, the crusaders and Venetians resolved to take the city for themselves. After a failed assault on April 9, they broke through the harbour walls on April 12, and the city fell.
The plunder that began on April 13 lasted three days. Crusaders stripped Hagia Sophia, where a prostitute was reportedly seated on the patriarch's throne. The historian Niketas Choniates, who fled the city, wrote that even the Saracens would have been more merciful. Relics were carried off across Western Europe. A Latin Empire ruled the city until the Byzantines retook it in 1261.
Key people: Enrico Dandolo, Boniface of Montferrat, Baldwin I of Constantinople, Alexios V Doukas