The document discusses the Fourth Crusade from 1201-1204. It was intended to strike at Egypt but instead attacked and sacked Constantinople, the largest Christian city, after the Crusaders grew angry that the Constantinople rulers could not pay the promised rewards. This caused a major rift between the Roman Catholic and Greek Orthodox churches. A fifth crusade from 1217-1221 followed but also failed to achieve long-term success, capturing the city of Damietta in Egypt but ultimately being defeated by Muslim forces.