Discuss the impact of the Crusades on the Byzantine Empire.

The question requires that candidates offer a considered and balanced review of the impact of the Crusades on the Byzantine Empire. Candidates may approach the question in a variety of ways, adopting a chronological approach or a thematic approach. For example, they could categorize the impact as positive and negative. Pressures on the Byzantine Empire due to the expansion of Islam were relieved by the First Crusade and the establishment of the Crusader states. However, the treaty between Constantinople and Saladin (Salah ad-Din) in 1187, through which the Byzantines agreed not to help the Crusaders, indicated the extent to which the Byzantines now regarded the Crusades as a negative force. The Fourth Crusade sacked Constantinople in 1204 and this was arguably the greatest impact of all the Crusades, as it dramatically weakened the Byzantines and contributed to their ultimate collapse in 1453.