The First Crusade began when Pope Urban II and a preacher named Peter the Hermit convinced the European people that all the evil in the world was due to the fact that Muslim people had control over the Holy Land. Pope Urban II offered absolution or indulgences to any participants.
In 1054, the Greek Orthodox Church and the Roman Catholic Church cut ties. Soon after, the Greek Orthodox Church came under attack from Muslims in Turkey, Albania and Bulgaria. They made a treaty with the Roman Catholic Church to receive an army to help them fight the Muslims. Pope Urban II hoped to reconcile the two churches and raise an army under the command of the papacy. He decided to first defeat the Muslims in Turkey and then move to Jerusalem to claim Palestine as a Christian country.
Europe was in a constant state of war and many errant knights were terrorizing Europe. The Pope believed the Crusade was the appropriate answer to whet their appetites for battle. To win the people, Peter the Hermit began to spread the idea that the world would finally be a peaceful place if the Holy Land was rescued from the hands of the Muslims and converted to a Christian beacon. When this tactic was not as successful as planned, Pope Urban decided to provide the pardoning of sin to any who participated in the Crusade, so they would not be eternally damned, which attracted many immoral and corrupt people to join the cause.