They knew little about the Byzantine Empire or its religion, Eastern Orthodox Christianity. Few Crusaders understood or had much sympathy for the Eastern Orthodox religion, which did not recognize the pope, used the Greek language rather than Latin, and had very different forms of art and architecture. They knew even less about Islam or Muslim life. For some the First Crusade became an excuse to unleash savage attacks in the name of Christianity on Jewish communities along the Rhine.[12]

wars undertaken in pursuance of a vow, and directed against infidels, i.e. against Mohammedans, pagans, heretics, or those under the ban of excommunication.[13]

For you must hasten to carry aid to your brethren dwelling in the East, who need your help, which they have often asked. For the Turks, a Persian people, have attacked them I exhort you with earnest prayer - not I, but God - that, as heralds of Christ, you urge men by frequent exhortation, men of all ranks, knights as well as foot soldiers, rich as well as poor, to hasten to exterminate this vile race from the lands of your brethren Christ commands it. And if those who set out thither should lose their lives on the way by land, or in crossing the sea, or in fighting the pagans, their sins shall be remitted. Oh what a disgrace, if a race so despised, base, and the instrument of demons, should so overcome a people endowed with faith in the all-powerful God, and resplendent with the name of Christ. Let those who have been accustomed to make private war against the faithful carry on to a successful issue a war against the infidels. Let those who for a long time have been robbers now become soldiers of Christ. Let those who fought against brothers and relatives now fight against these barbarians. Let them zealously undertake the journey under the guidance of the Lord.[14]

It was the Crusaders’ task to defeat and defend against them. That was all. Muslims who lived in Crusader-won territories were generally allowed to retain their property and livelihood, and always their religion.

The scenes of carnage which followed belong to the many dark pages of Jerusalem's history and showed how, in the quality of mercy, the crusading knight was far below the ideal of Christian perfection. The streets were choked with the bodies of the slain. The Jews were burnt with their synagogues.... As if to enhance the spectacle of pitiless barbarity, Saracen (i.e. Muslims) prisoners were forced to clear the streets of the dead bodies and blood to save the city from pestilence. "They wept and transported the dead bodies out of Jerusalem," is the heartless statement of Robert the Monk. ... "They cut down with the sword," said William [archbishop] of Tyre, "every one whom they found in Jerusalem, and spared no one. The victors were covered with blood from head to foot." In the next breath, speaking of the devotion of the Crusaders, the archbishop adds, "It was a most affecting sight which filled the heart with holy joy to see the people tread the holy places in the fervor of an excellent devotion."[15]

The illegitimate offspring of the Crusaders by Moslem women, called pullani, were a degenerate race, marked by avarice, faithlessness, and debauchery.[16]

And, if you desire to know what was done about the enemy whom we found there, know that in the portico of Solomon and his Temple, our men rode in the blood of the Saracens (i.e. Muslims) up to the knees of the horses.[17]

...there [in front of Solomon's temple] was such a carnage that our people were wading ankle-deep in the blood of our foes, and after that "happily and crying for joy" our people marched to our Saviour's tomb, to honour it and to pay off our debt of gratitude.

It was impossible to look upon the vast numbers of the slain without horror; everywhere lay fragments of human bodies, and the very ground was covered with the blood of the slain. It was not alone the spectacle of headless bodies and mutilated limbs strewn in all directions that roused the horror of all who looked upon them. Still more dreadful was it to gaze upon the victors themselves, dripping with blood from head to foot, an ominous sight which brought terror to all who met them. It is reported that within the Temple enclosure alone about ten thousand infidels perished.[18]

The Christian occupation of Palestine did not bring with it a reign of peace. The kingdom was torn by the bitter intrigues of barons and ecclesiastics, while it was being constantly threatened from without. The inner strife was the chief source of weakness.[19]

The great Muslim sanctuaries became Christian churches, and in 1149 the Church of the Holy Sepulchre as it exists today was consecrated. Muslims and Jews were barred from living in the city.[20]

God aroused the spirit of the prince of the Ishmaelites [Saladin], a prudent and courageous man, who came with his entire army, besieged Jerusalem, took it and had it proclaimed throughout the country that he would receive and accept the entire race of Ephraim, wherever they came from. And so we came from all comers of the world to take up residence here. We now live here in the shadow of peace.[22]

On 2 October 1187 Saladin and his army entered Jerusalem as conquerors and for the next 800 years Jerusalem would remain a Muslim city... Saladin kept his word, and conquered the city according to the highest Islamic ideals. He did not take revenge for the 1099 massacre, as the Koran advised (16:127), and now that hostilities had ceased he ended the killing (2:193-194). Not a single Christian was killed and there was no plunder. The ransoms were deliberately very low...[23]

The Crusades were fascinated by a Muslim leader who possessed virtues they assumed were Christian. To them to his Muslim contemporaries and to us, it still remains remarkable that in times as harsh and bloody as these a man of great power should have been so little corrupted by it."[24]