Europe in the medieval period had Christians and Muslims as their citizens. There was a small Jewish community too. Paganism was practised and there were few other minor religions. When it is mentioned as Europe the countries close to Europe and under the control of the European countries are also taken into consideration. As in most other aspects of historical importance it was the fall of the Roman Empire that brought about the changes in the religious influence over the people. The fall of the Roman Empire brought an end to formal Christian religion. Anglo Saxon invaders dominated the island of England.
It was only in the late sixth and seventh centuries that Christianity began to exert its power and by the end of the seventh century the missionaries of Pope Gregory I managed to convert most back to Christianity. The Scots-Irish monks still had control over the north of England. All these changes confused the people as they could not let go of their native religious ceremonies and local practises. When the Vikings invaded in the eighth and ninth centuries they brought back paganism in North East England. So it was again another wave of conversions. The Church had a great influence on the English State when Christianity was at its peak. The Pope and the bishops played an important role in governance. They supported kings who favoured the church and tried to dethrone ones who were not supportive.
The period in discussion also saw the rise of Islam. Prophet Mohammed was born and formulated the new order called Muslims and over a period of few years Islam spread widely and even entered Europe. It was in 732 AD that the massive progress of Muslims into Europe was stopped by Franks in the Battle of Tours. All was not fine for the Muslims after the death of Prophet Mohammed. There was split amongst the followers of the Prophet, on who should be the successor. Initially it was a political rift but later theological and juridical changes were brought about in the two factions. One was the Sunni faction and the other was the Shia faction. They became warring communities and the Umayyad dynasty was driven off from the Muslim lands and they created a base in Europe. In the Muslim community it was the Caliph who had control over the people. Be it Christians or Muslims, the clergy had great influence on the state.