In the middle of the XI century. Pope Gregory VII with an iron hand brought order in the Catholic Church. He resolutely demanded that kings and big feudal lords should not interfere in church affairs, and that the popes and bishops should choose the clergy. The pope claimed that monarchs should be his vassals and pay the church a lot of money. In the XII century. the pope and royalty made concessions to each other – divided among themselves the right to appoint and dismiss bishops.
At the end of the XI century. The popes have already acquired such an influence in society that they raised Europe to war against Muslims. They reasoned like this.
The feudal lords will still fight against each other. Is it not better to direct their military zeal against the Gentiles and thus strengthen the Catholic Church?
The... occasion for inciting religious war turned out to be excellent. At the end of the XI century. Byzantium appealed to the European kings and the pope for military assistance against the belligerent Seljuk Turks. Kings hesitated, but Pope Urban II urged Christian Europe to free the Seljuks from the Holy Sepulcher – the largest Christian shrine. The pope promised all participants of the campaign against Jerusalem a free remission of sins, and the souls of those who perish in the campaign – paradise. But the most tempting was another promise Urban II: “He who is here woeful and poor, there will be cheerful and rich.” Who did not want to be “cheerful and rich”? Many knights, townspeople, clerics and peasants immediately swore to save the Holy Sepulcher and sew on their clothes a cross – the then symbol of victory.