Excerpts from Books and Wikipedia
"Pope Urban II addressed a throng of bishops, nobles, and citizens and called on the knights of western Christendom to stop fighting each other. Rather, he said, they should turn their swords to God's service by freeing Jerusalem from the Muslims. . . . Urban was responding to an appeal from the Byzantine emperor Alexius II for military aid from the West. . . . Since then reports of Muslim attacks on Christian pilgrims had aroused a new mood of religious fervor in the West, and the pope's call met with enthusiasm. By 1096, thousands of people, mostly from France, the Low Countries and Germany, had taken a solemn oath to make the long and dangerous journey to the Middle East." [1001 Days] "Alexius needed mercenaries--but Urban II transformed it into something new. . . In November of 1095, at Clermont in Western Francia, Urban II announced that it was not only time to help Byzantium in its battles against the Turks . . . But also time to recapture Jerusalem from the hands of Muslims . . . 'All who die by the way, whether by land or sea, or in battle against the pagans, shall have immediate remission of sins,' Urban promised."