Please protect me, they are trying to blind me and kick me out of my office!
Okay, I agree.
God made me emperor!
No he didn't! The Church did!
I have supreme authority over Church and secular leaders!
Also, only the Pope alone has the power to choose bishops!
Charlemagne was a king in Europe who wanted to establish a Christian Empire. In 799, Pope Leo III asks for Charlemagne's protection from being removed. Charlemagne agrees and is crowned Holy Roman Emperor. As a result, the Pope won power to crown emperors and this angered the Byzantine Emperor.
You are excommunicted!
Charlemagne believed that God had made him emperor so that on Earth, he could do God's work. However, the Pope believed that the Church made him emperor. Two-hundred years later, the differences ended with a fight between an emperor and the Pope.
No! Choose me!
In 1073, Pope Gregorymade a list of rules demanding his supreme authority over Church and secular leaders. He also declared that only the Pope alone had the privilage to choose bishops. King Henry IV reacted by not following the rules and named his own bishop for the city in Milan, Italy.
Yes, my king
Let's go army! We will force the Pope from office!
The conflict all started when Pope Gregory named another bishop to rival with Henry's. Then, Henry tried to remove Gregory as Pope, but then Gregory excommunicated Henry which was a big deal back then. He also freed Henry's subjects from their feudal oaths of loyalty to the emperor.
All across Europe, the clergy and secular members took the Pope or the emperor's side. Henry then went to visit the Pope in an Italian castle to stop his excommunication. Before the Pope saw and forgave him, he stood outside the castle while it was snowing for 3 days.
The conflict between them ended with the king taking his army to Rome to force the Pope from their office. The Concordat of Worms allowed the Church to appoint bishops. This was not a success because later on they still had conflicts.