The armies of the First Crusade (1096-1099)—under the principal leaders Raymond of Toulouse, Robert of Normandy, and Godfrey of Bouillon— crossed Europe to Constantinople, assembling there in the spring of 1097. They proceeded across the Bosporus in May of that year and entered the domain of Kilij Arslan, Seljuk sultan of Rum. The crusaders first forced him to surrender Nicaea, his capital city, on June 19, after a siege of more than seven weeks. The anonymous author of Gesta Francorum ( Deeds of the Franks ), reputedly a follower of Bohemund of Taranto, paid tribute to the fighting qualities of the Turks:

What man is so learned and wise that he can describe the prudence and warlike skill and courage of the Turks? Certainly if they had always been firm in Christianity and had been...