While the first three Crusades were launched in an effort to reclaim Jerusalem from Muslims, the Fourth Crusade, begun in 1202, pitted Christians against Christians: Roman Catholics against Orthodox.
On the Conquest of Constantinople is one of the most important historical sources on the Fourth Crusade and the Sack of Constantinople.
The Fourth Crusade was meant to strike Egypt, but a financial crisis and a disastrous miscalculation left the crusaders trapped in debt. When a Byzantine prince promised gold, soldiers, and supplies ...