In a sermon at the Council of Clermont on 26 November 1095, Pope Urban II painted a gruesome image of the Muslim occupation of Jerusalem and promised remission of sins for all those who would go on a crusade to liberate the Holy Land. Thousands of knights responded to this call to arms, and the result was the First Crusade (1095-1099).

From the confines of Jerusalem and the city of Constantinople a horrible tale has gone forth and very frequently has been brought to our ears, namely, that a race from the kingdom of the Persians [that is, the Seljuk Turks], an accursed race, a race utterly alienated from God, a generation forsooth which has not directed its heart and has not entrusted its spirit to God, has invaded the lands of those Christians and has depopulated them by the sword...