The First Crusade may be considered the only really successful crusade in that it achieved its stated goal, but it demanded great courage and stamina of its participants in their journey to the Holy City of Jerusalem, fighting their way through an unforgiving hostile territory. But courage and stamina by themselves were not sufficient to guarantee any manner of success. The additional quality that the crusaders needed, and which was to be the most valuable to them, was faith: faith in their God, who would deliver the Holy City to them despite the horror and hardship that they suffered. Their courage and strength of the natural world lent them much of the determination to persevere through heat and thirst, cold and hunger, battle and bloodshed; but what they accepted as God's will gave them a perception of the power of the supernatural. And without the supernatural the First Crusade would have disintegrated long before it reached Jerusalem.

The origin of the First Crusade lay in the appeal for help from Alexius I, emperor of Byzantium and head of the Greek Christian Church, to Pope Urban...