Out of control in Byzantium
Venice had staked its whole economy on this contract, and neglected trade for over a year while building ships, assembling supplies, and training sailors to fulfill their part. The Venetians had to be paid or be ruined, and demanded the full price agreed on. But the crusaders couldn’t raise it.
The crusade’s leader, Boniface of Montferrat, was approached by two exiled Byzantine royals, the ex-emperor Isaac II Angelos and his son Alexios. Isaac had been deposed (and blinded for good measure) by his brother, who was now Emperor Alexios III Angelos. The two exiles insisted that young Prince Alexios was the rightful emperor, loved and supported by the people of Constantinople, and they offered enormous rewards to the cash-strapped crusaders and the Venetians for taking up his cause: piles of silver, fleets of ships, hordes of soldiers, and—a boon that would hopefully calm the Pope’s wrath over attacking yet more fellow Christians—the submission of the Eastern Orthodox Church to the authority of Rome.
This offer had great appeal to the Doge of Venice, Enrico Dandolo, not only because it held out the only visible prospect of restoring the Republic’s economic health, but also because commercial relations between the Byzantine Greeks and the increasingly pushy Latins had become difficult. Not long before this, the Venetian trading community had been expelled en masse from Constantinople. They were now back in, but very uneasy about their position. Trade with the East was the foundation stone of the Venetian economy, and at this period a foothold in Constantinople was a necessary condition for it. (In addition, Dandolo, who had served on a Venetian embassy to Constantinople, seems to have had a deep personal dislike for the Byzantines.)
When the Latin forces arrived at Constantinople in June, 1203, they learned—to their apparent surprise—that Prince Alexios was not quite the people’s favorite he had claimed to be. So they besieged the city. They didn’t quite succeed in taking it, but they did breach the defenses temporarily. While inside the walls, they attempted to fend off counterattacks with a “wall of fire,” which got out of control and burned quite a bit of the city. About 20,000 people lost their homes.
A further assault scared Alexios III into running away. Prince Alexios (henceforth Alexios IV) and his father, Isaac II, were proclaimed co-emperors. The crusaders and Venetians stayed in their camp outside the city, but had free access. They were ready to collect their reward, but Alexios III had taken most of the treasury with him, and the new emperor couldn’t pay the enormous sums he had promised to the Latins. When they began to make threats, he had many of Byzantium’s treasures, including precious icons and other religious objects, melted down, but this didn’t yield enough to pay the debt, and it also cost Alexios IV whatever support he might have been able to find among the city’s people.
Street fights between Greeks and Latins became commonplace. In January of 1204, Isaac II died, and in the ensuing riot the people deposed Alexios IV. The imperial chamberlain, Alexios Doukas, had himself proclaimed Emperor Alexios V—and, lest any uncertainty linger, executed his hapless predecessor.
Alexios V fled, and the victorious Latins subjected Constantinople to three days of sacking. Its citizens suffered the atrocities usual on such occasions, and the city was plundered of far more than enough silver and gold to pay the crusaders’ debt to Venetians. They and the crusaders shared the very large remainder. Works of art handed down from Greek and Roman times were packed up and shipped west (for example, the four bronze horses from the Hippodrome, now to be seen on the façade of St. Mark’s Cathedral in Venice).
Crete was awarded to Boniface, but he was more interested in setting up the Kingdom of Thessalonica in the generous slice of Greece that was now his. (You can guess who became its king.) So he didn't mind selling Crete to the Venetians, and only charged them 100 silver marks. (As a measure of what a silver mark was worth, the Venetians’ original price for supplying transportation and military assistance to the crusaders was 85,000 of them. The total amount of wealth stolen from Constantinople has been estimated at 900,000.)
Pope Innocent, who had up to this point perhaps deserved his name, denounced the crusaders furiously at the first news of their conquest, but later became inclined to take a more positive view of the affair. Some accounts attribute this to the generous shares of booty that arrived in Rome to adorn the Vatican and add to its coffers. Others, perhaps more accurately, explain the pope’s change of mood as based on his hope that Vatican authority over the Eastern Orthodox Church was now definitively established—Innocent was the first pope who got to appoint a Patriarch of Constantinople. But that authority lasted only as long as the Latin Empire, which the Greeks reconquered in 1261.