The First Crusade was an extreme and explosive upheaval of religious euphoria that reached a state of perfection in a brilliant military feat. Pope Urban II, in his call for crusade at Clermont in late 1095, touched a sensitive point in Western Christianity, unleashing a power that far exceeded the results of his desires and proved difficult to control. Both honorable and selfish motivation drove multitudes of crusaders to travel east. Despite considerable obstacles, most of these military powers managed to arrive in the Holy Land; in mid-1099 they broke the walls of Jerusalem and in a paroxysm of madness prevailed over the Muslims and conquered the Holy City. But in this essay I focus on why so many Western Europeans joined this movement. The popularity of the First Crusade is demonstrated by the fact that people from all socio-economic backgrounds responded to the Pope's call. The poor joined the First Crusade through movements such as the People's Crusade led by Peter the Hermit. However, figures at the top of the social ladder such as Godfrey of Bouillon or...