Scenes from the Crusades - Illustrations by Gustave Dore
The Fourth Crusade was meant to retake the Holy Land from the Moslems, but instead the Venetians steered it against Constantinople, their great economic rival. Constantinople (now Instanbul) was the capital of the Byzantine Empire, a Christian kingdom. So instead of fighting the Muslims, the Christian crusaders fought against fellow Christians. They captured Constantinople and greatly weakened the Byzantine Empire, thus paving the way for the Moslem conquest of all of Turkey and the Balkans.