Pope Urban II (1088-99), who next took up the idea, was animated not so much by the political considerations of Gregory as by actual religious impulse. From the Church should come the impelling force; on the secular powers rested the actual execution of the plan. Before this, Norman knights had engaged in conflict with the infidel, and the conception of a crusade against the Saracen was therefore no absolute novelty to the nations of the West.
The Byzantine emperor Alexius I was quite aware of this when he turned to Urban for aid against the Turks in 1094, and met with a ready response from the general religious enthusiasm, from the ambitions of the Church, and from the lust for adventure and conquest. When the Greek ambassadors arrived Urban was preparing for the Council of Clermont; and there before great throngs the pope first reached the crusade, November 26, 1095, in words which have not come down, but which stirred the mighty multitudes to frenzied enthusiasm.
The number of those who assumed the crusader's cross increased daily, and the movement, soon passing beyond papal restraint, seized upon the lower classes. The peasant exchanged his plow for arms and was joined by the dissatisfied, the oppressed, and the outcast; members of the lower clergy, runaway monks, women, children gave to this advance-guard of the crusading army the character of a mob, recognizing no leadership but that of God.
This undercurrent of opposition to the pope gave rise to the legend, which is still current, that not Urban, but Peter the Hermit (Peter of Amiens) was the true representative of the crusading idea. Peter was one of the leaders of the fanatical bands, whose contribution to the enterprise was a story of an alleged personal appearance of Jesus, giving him commission to acquaint Christendom with the sad condition of the Holy Land. After the wildest excesses, in which the Jews appear as the principal sufferers at their hands, these tumultuous hosts found a pitiful end in Hungary and beyond the Bosporus.
The real crusading armies set out in 1096. The main contingents were men of Lorraine under the brothers Godfrey of Bouillon and Eustace and Baldwin of Boulogne; Flemings under Count Robert II of Flanders; northern French under Robert of Normandy (older brother of King [[William II of England), Stephen of Blois, and Hugh of Vermandois (younger brother of King Philip I of France); Provencals under Raymond of Toulouse; and Normans of Italy under Bohemund of Taranto and Tancred. The Christian cause suffered from dissensions among the leaders, and it had to contend against the machinations of Alexius I, who was roused to a sense of danger to his realm by the presence of the Western armies.
Nicaea, capital of the Seljuk "Sultan of Rum" Kilij Arslan I,was taken in early 1097, and Kilij Arslan himself was defeated at Dorylaeum. The Crusaders then marched across Asia Minor. At this point Baldwin of Boulogne set off on his own, and conquered Armenian lands around the Euphrates, which became the County of Edessa. The main Crusader army, meanwhile, marched on to Antioch, which was captured after a long siege on June 3, 1098. On June 28 Antioch was successfully defended against the army of the Atabeg of Mosul, thanks largely to the efforts of Bohemond, who claimed the city for himself as Prince of Antioch. After a break, the rest of the Crusader army marched on to Jerusalem, which had, in the meanwhile, been recaptured by the Fatimids of Egypt. After a siege, Jerusalem was taken on July 15, 1099. The Crusaders massacred the whole Muslim and Jewish population, men, women and children. The Jews were burned alive in their main synagogue where they had fled. In the days following the massacre, Godfrey of Bouillon was made Protector of the Holy Sepulcher. In the last action of the Crusade, he led an army which defeated an invading Fatimid army at Ascalon. Godfrey died in July, 1100, and was succeeded by his brother, Baldwin I of Edessa, who took the title of "King of Jerusalem. Baldwin and his successors, Baldwin II (d. 1131), and Fulk (d. 1143), extended the boundaries of the Kingdom of Jerusalem through successful warfare.
The kingdom drew strength from the influx of new crusading forces, from the presence of the Italian merchants who established themselves in the Syrian ports, and from the religious and military orders of the Knights Templars and the Knights of St. John.