The eleventh century is nearing its end. Jerusalem, a place where people of different faiths had once lived peacefully together, is a city holy to Jews, Christians and Muslims. Since 638, when Caliph Omar (Muhammad's successor) captured the city for the Muslims, it has been under Islamic rule.
Pope Gregory VII is concerned about continued Muslim control (the link depicts Omar’s code/covenant) over Christianity’s most sacred sites and relics. In a 1074 letter, the pope issues the
first call for what would later be known as a crusade:
He [a visitor to the pontiff] repeated what we had heard from many others, that a pagan race had overcome the Christians and with horrible cruelty had devastated everything almost to the walls of Constantinople ... we should lay down our lives to liberate them.