The Fourth Crusade started in 1202, when Pope Innocent III (p.1198-1216), seeking to build on the success of the Third Crusade preached a new Crusade to recover the Holy city of Jerusalem. The kings of Europe were too involved in personal quarrels to participate, so the mantle was taken up by a group of the lesser, mostly French, nobility.
At first, the Crusade appeared to be going nowhere with the major monarchs of Europe either at war, as England and France were, or in flux as was the Holy Roman Empire, with rival claimants to the throne. Thibault of Champagne (d. 24 May 1201) persuaded several members of the minor French nobility to take the cross, the most notable of whom, were Louis of Blois and Baldwin of Flanders. These three lords decided at a council in early 1200 to send a delegation to Venice seeking transport to the Holy Land. The Doge of Venice Enrico Dandolo (1192-1205) agreed to transport the Crusaders and provide a fleet of fifty Venetian manned ships for the sum of 85,000 marks.
The Crusade leaders expected the Crusaders to help underwrite the cost of the Crusade by contributing to the costs of passage, but by June 1202, only 11,000 Crusaders had arrived, barely one third of the expected number.Â This point is where the Crusade lost its direction, because of the smaller than expected number of Crusaders the leaders could not make the full payment. The Doge of Venice proposed a solution to get the Crusaders out of their financial difficulties. The Venetians wanted the Crusaders to assist them in recovering the rebellious city of Zara on the Adriatic coast.
Zara was under papal protection but the papal legate, Cardinal Peter Capuano realized that if the Crusaders did not assist in the capture of Zara the entire enterprise would be put at risk so he chose to remain silent about papal opposition to the attack on Zara. The fleet sailed in November 1202, and the Zarans’ offered to surrender almost immediately, until counseled by Simon de Montfort the Elder (1160-1218) to fight the Venetians and assuring them the Crusaders would stand by.Â In any event, Simon removed his forces but the majority of the Crusaders took part and the Crusaders and Venetians were promptly excommunicated by Innocent III after the city capitulated. After receiving a letter, begging for forgiveness the pope absolved the Crusaders but confirmed the excommunication of the Venetians and ordered the crusaders to have no more to do with the Venetians after they reached the Holy Land.
Zara was but the first incident in the soap opera that the Fourth Crusade would become. After Zara, the crusading army found themselves short of provisions and funding, at this point the Byzantine prince Alexius Angelus (r.1203-1204) approached the Crusaders and said that if they would help him recover the Byzantine throne from his usurping uncle Alexius III Angelus (r.1195-1203), he would underwrite the continuation of the Crusade and join them providing an additional 10,000 troops.Â There was much debate among the Crusaders about whether to accept the offer, but it was eventually accepted because the Crusade leaders felt they had no choice if they wished to continue the Crusade.
The Crusaders arrived at Constantinople in the summer of 1203 and assaulted the walls on July 17 but were repulsed. The Byzantines deposed the usurper and opened the gates to the city whereupon the Crusaders placed Alexius on the throne as Alexius IV as co-emperor with his blind father Isaac II Angelus (r.1185-1195 & 1203-1204). Alexius IV immediately set about repaying the Crusaders however; he had to repay them in installments because of the amount owed. Alexius asked the Crusaders to winter in Constantinople to allow him time to raise the money they reluctantly agreed, being anxious to get on with the Crusade. Alexius housed the crusade in Galata, across the Golden Horn from the city, while he tried to come up with the money.
In the summer of 1203, a fire set by the Venetians devastated the northern part of Constantinople, which further increased the localâ€™s hatred for the invaders. Alexius had a hard time collecting the required sums over the winter and the crusaders began to pillage the countryside to pay themselves. In January 1204, Alexius was overthrown and murdered by a palace functionary, who crowned himself Alexius V Mourtzouphlus (1204).
After the overthrow of Alexius IV, the crusaders knew they would not receive payment and decided to conquer the city and place a Latin on the throne of Byzantium. They attacked the city on April 9 but were repelled; on the night of April 12, they tried again and were successful. Mourtzouphlus was overthrown by the Byzantines, and they offered the throne to Boniface of Montferrat, one of the chief crusaders but he could not accept as the crusaders had agreed to elect one of their own. After taking the city the crusaders proceeded to sack it, Constantinople was one of the richest cities in the world and the crusaders looted, pillaged, and destroyed for three days. They carried off most of the treasures of the city to the west such as the four bronze horses that adorn St. Markâ€™s Cathedral in Venice to this day.
The Crusaders elected Baldwin of Flanders (1172-1205), who took the throne as Emperor Baldwin I.Â Thus was created the Latin Empire of the East, which was to last until 1261 when the Byzantines, who had lived in exile in Nicaea would reclaim their empire. The Byzantine Empire was fatally weakened, and from the restoration in 1261, would be in a gradual decline until the final Turkish conquest of the city in 1453. The Fourth Crusade ended with very few crusaders ever reaching the Holy Land most returned home after the fall of Constantinople or carved out lands for themselves among the Greeks.
 Madden, Thomas F. The New Concise History of the Crusades. p. 100
 Madden, Thomas, F. ed. The Crusades: An Illustrated History, pp. 103-104
 Ibid., p. 106
 Madden, Concise History. p. 105
 Ibid., pp. 113-114
 Ibid., p. 119