Charlemagne and Pope Leo III formed the Holy Roman Empire in order to unify the empire that was once ravaged by barbarians. The Pope had helped in defending the lands against the savages, and now he has crowned an emperor.
After both of those men died, their successors could not carry on the dream. While the Romans valued unity, the Teutons liked to divide their inheritance among their sons. First, Louis the Pious succeeded his father Charlemagne. Then, he had two sons: Louis and Lothair. He then divided the empire among them, and then he had another son, Charles the Bald. After the father's death, Louis owned the western empire, Charles inherited the east, and Lothair had everything else and was declared emperor.
Louis and Charles met in Strasbourg in 842 and took an oath to be loyal to each other until they defeated Lothair. Lothair threw up the white flag, and they formed the Treaty of Verdun in 843. They no longer shared the continent. Charles the Bald controlled what is now France, Louis controlled what is now Germany, and Lothair took Italy and everything else. This is why they are separate countries today.
The practice of dividing land among people became the trend. After the Roman Empire got so big, it could not take care of everybody anymore. "Feudalism in one form or another always arises when a central government becomes weak and can no longer exercise effective authority over the areas under its control," (Cairns, 192). People had to make their own living off of the land, and they divided the land between men who owned the land. They pretty much had their own private states. The lords who owned the land let vassals and serfs live on the land in exchange for helping on the farm. This was a mini-communism. The government owned the land and provided for the serfs. The serfs had all things distributed among them and they were basically slaves. They were loosely united until William the Conqueror solidified the feudal pyramid.
At some point, some people donated their land to the Pope in order to pay for some indulgence. The Roman Church now owned a lot of real estate. It was influenced by the feudal system. The abbots and bishops tended the land, and clergy were like the serfs. They were also peaceful.
The bad news: this began to secularize the church. The good news: it did help them reach out to the people some. They would open sanctuaries, monasteries, and convents for refugees who needed homes.
The bad news again: the lords could gain land and prestige through service in the church. Since they gave the biggest donations, they could have a say getting bishoprics and abbeys for their relatives who had little interest in spiritual matters. It was just a job to them.
An investiture controversy arose: could the feudal lord or the pope grant these feudal church leaders the symbols of authority? This made relations between Church and state rocky. The Church did have an influence in social activism. They made the Peace of God, an agreement to ban private quarrels between lords. They also enacted the Truce of God, saying that the lords could not fight each other except on Tuesdays. This prevented much bloodshed. And, of course, there were homes for the destitute.
At the same time, Slavs, Vikings, and Magyars continued to attack the empire, dividing attentions between homeland security and batting off the invaders. Many of the invaders settled in England and Normandy: the Anglo-Saxons and Vikings respectively. Slavs and Magyars occupied south-central Europe. They posed a threat to the Papal power and broke the Eastern empire.