There was once a devout Christian ruler named Charlemagne wanted to make the church stronger to thank God. Pope Leo III had fled his home due to rivals and Charlemagne gave him a place to stay.
During this time, Popes could crown emperors so Pope Leo crowned Charlemagne and this effected two consequences. It strengthened the power of the church in Western Europe by establishing the principle that only the pope could crown emperor.
However, this idea created conflict in Eastern Europe of the pope deciding who is crowned emperor.200 years later after Charlemagne's coronation, these different views lead to a dramatic clash between an emperor and the pope
In 1073, Pope Gregory declared that the pope alone had the power to choose bishops and to have the power to remove emperors from the throne.
Pope Gregory and King Henry both wanted different things and thought as this new idea to be opposites from each other. Pope Gregory thought it was okay but King Henry didn't like it. This caused the people across Europe to end up taking sides.
Later, the Holy Roman Empire reached an agreement called the Concordat of Worms. This gave the church the sole authority to appoint bishops but also allowed emperors to give fiefs or grants of land to bishops to win their loyalty. Despite the agreement, popes and rulers continued to have conflicts.