On 12 April 1204, the Crusaders of the Fourth Crusade captured Constantinople, the capital of the Byzantine Empire and would establish the short lived Latin Empire which lasted until 1261.
The crusaders had sailed from Venice on 24 June 1202 with the intent to attack Cairo. They had been explicitly banned by Pope Innocent III from attacking any Christian states. However, when the crusaders began assembling, they had requested from Venice far more ships to be constructed than they would eventually need. Venice built ships for 33,500 crusaders but when the crusade set sail there were only 12,000 soldiers. Despite not needing the additional boats, Venice required that the crusaders pay for all ships constructed. This reduced many of the crusaders to poverty and placed a severe economic strain on the Venetians. When Byzantine prince Alexius Angelus approached the Crusaders with an offer to provide them with money, men and ships in exchange for helping him to overthrow Emperor Alexius III and restore Isaac II, the father of Prince Alexis, to the throne – the Crusaders saw an opportunity to recoup their losses.
While the initial motive of the crusader attack on Constantinople was to restore Isaac II to the throne, after the Crusaders overthrew Alexius III, prince Alexius – now Alexius IV, was unable to deliver the promised wealth to the Crusaders. Moreover, Alexius IV became extremely unpopular in Constantinople and was eventually strangled to death and replaced by one of his courtiers who would become Alexius V. The Crusaders then demanded that Alexius V honor Alexius IV’s agreement, but Alexius V refused. Therefore, the Crusaders continued their attack on Constantinople to get they money they believed they were owed.
It should be noted that Pope Innocent III had sent explicit letters forbidding an attack on Constantinople but these letters were kept hidden by the clergy participating in the siege of Constantinople.
When the Crusaders finally took Constantinople, the destruction was enormous. Fires in the city would leave 15,000 homeless. The sack of the city lasted three days, during which the Crusaders violated churches and destroyed the Library of Constantinople. One account writes:
the French and others destroyed indiscriminately, halting to refresh themselves with wine, violation of nuns, and murder of Orthodox clerics. The Crusaders vented their hatred for the Greeks most spectacularly in the desecration of the greatest Church in Christendom. They smashed the silver iconostasis, the icons and the holy books of Hagia Sophia, and seated upon the patriarchal throne a whore who sang coarse songs as they drank wine from the Church’s holy vessels… The Greeks were convinced that even the Turks, had they taken the city, would not have been as cruel as the Latin Christians.
When Pope Innocent III heard about what the Crusaders had done, he was furious and asked:
How, indeed, will the church of the Greeks, no matter how severely she is beset with afflictions and persecutions, return into ecclesiastical union and to a devotion for the Apostolic See, when she has seen in the Latins only an example of perdition and the works of darkness, so that she now, and with reason, detests the Latins more than dogs? As for those who were supposed to be seeking the ends of Jesus Christ, not their own ends, who made their swords, which they were supposed to use against the pagans, drip with Christian blood, they have spared neither religion, nor age, nor sex. They have committed incest, adultery, and fornication before the eyes of men. They have exposed both matrons and virgins, even those dedicated to God, to the sordid lusts of boys.
Although the Byzantines would eventually recover Constantinople, the Empire was permanently weakened and the destruction of the Fourth Crusade would contribute to the eventual fall of the Empire in 1453. Furthermore, while the schism between East and West could be said to have begun in 1054, it was the sack of Constantinople that made that rupture permanent.
The memory of the sack of Constantinople is still strong among the Orthodox. Twice, Pope John Paul II issued an apology for what the Catholic West had done. In April 2004, Orthodox Ecumenical Patriarch Bartholomew I formally accepted Pope John Paul II’s apology.