During the Medieval Times, the power of Christendom started to deteriorate across the Roman Empire. The King and the Pope, being two separate dictators in the same Empire, ran into some conflict on control over the clergy. The result is the ultimate showdown between a political leader, and a religious leader.
The church becomes entangled in the feudal system during the 10th century. Many members of the clergy fall under control of local landlords as vassals. Landlords then had complete control over these vassals that were once bishops, abbots, and priests. Landlords often chose people from the clergy for political non-religious reasons, for they had the ability to be responsible and loyal. This results in the decline of spiritual rigor.
Lay investiture went on for a number of years before Pope Gregory VII, had something to say about it in the 11th century. Gregory VII declared the king’s role in Christendom; to establish peace and order, so the people could pursue a christian journey. If he doesn’t do that, he’s a tyrant. Gregory sent orders to King Henry IV that he should stop appointing the clergy. Henry responded with a blistering letter, and Gregory in turn issued an order telling Henry’s subjects that they were no longer required to obey him. Gregory excommunicated Henry, and also declared him deposed. Henry, faced with rebellion, must submit.
After many attempts to get back in office, Henry IV and Pope Gregory VII had a meeting and resulted in getting the excommunication lifted. This concluded in Henry getting excommunicated again, then driving Pope Gregory VII out of Rome. The new Pope Calixtus II and King Henry IV agreed on a Concordat of Worms, which ended lay investiture.
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