Charlemagne was a Christian ruler in Europe and the King of the Franks. His goal was to rule a Christian empire in Europe. He was known for his integrity and often lead his empire personally.
200 years later...
I don't think so, bub!
I hereby declare that I rule all people and not King Henry.
Pope Leo III came to him begging for protection. His own people were threatening to blind him and ban him from office. Charlemagne agreed and sent him back to his office with the protection of the king this marked the beginning of popes and kings working together.
Grrr!! Well then, excomunicate him!
I appoint a bishop to that city!
Sir, I don't think that will work very well for you. Oh, there are his armies approaching the castle right now.
Sir, I'm afraid King Henry has already appointed a bishop there.
However, Charlemagne believed he had more power than the Pope. Of course the Pope thought the opposite, which started a conflict. 200 years later, after Charlemagne and Pope Leo had both died, the pope and the emperor continued to fight each other for power.
In 1073, Pope Gregory issued a list of rules declaring his supreme power over both secular and non-secular rulers. King Henry was opposed to these rules because he thought it was an attack on his power. So he decided to ignore them and appointed a bishop which then started a conflict.
The conflict between Pope Gregory and King Henry was very snappy. King Henry appointed a bishop and then the Pope appointed a different bishop. People across Europe reacted by taking a side and listening to the bishop that their favored ruler appointed.
The conflict ended when King Henry took revenge and stormed the Pope's castle. he forced the Pope out of office which ultimately ended the conflict. Shortly after, The Concordat of worms was passed which gave the power of appointing bishops to the church. This was not a success. Popes and emperors still continued to argue after this event.