Foss, an independent historian, absorbingly tells the strange tale of Christendom's First Crusade (1097-99) to liberate Jerusalem and the Holy Land from Muslim rule. In an attempt to unify Latin Christendom and defuse the threat of a Muslim invasion from the East, Pope Urban II, in a speech at Clermont, France, in 1095, urged military leaders to form an army of liberation and free the Holy Land from Muslim control. The pope's speech sparked an excess of pious idealism that outstripped common sense: Invoking the protection of Jesus and the Virgin Mary, popular leaders like Peter the Hermit led the first Crusaders, unmilitary mobs of peasants, who indulged in a series of brutal atrocities (a sanguinary pogrom against the Jewish community of Mainz was only the most spectacular) before being scattered by Turkish forces. Knights like Stephen of Blois and Godfrey of Bouillon assembled a more professional but still motley Christian army, notable from the first for its violence and lack of discipline. Driven by an intense religious fervor, the Christian army conducted total war against Muslims and Jews, showing no mercy to the elderly, women, or children. They defeated the forces sent against them, captured the cities of Antioch and Nicaea, and concluded the campaign with a successful assault on the Holy City of Jerusalem. In each case, a wanton slaughter of the inhabitants followed. Through three years of costly struggle, faith that sometimes was little more than superstition sustained the Crusaders: After the fall of Antioch, a seer named Peter Bartholomew claimed to have uncovered the lance that pierced Jesus' side, which was believed to ensure the ultimate victory of the Crusaders. Foss's account points up the irony of this war, in which religion was pressed into the cause of violence and brigandry, and concludes that ""God--Allah--is not best served, if at all, by fighting."" A sobering narrative, well told, of a shameful episode that epitomized religious bigotry and intolerance.