The Catholic religion and its administration survived the collapse of the Roman Empire and remained an organized institution within the new barbarian realms. Bishops, who were principally implanted in the towns and often originated from the Roman aristocracy, played a central role in the fusion between the new conquerors and the submitted populations. The bishops and the pope (who originally was merely the bishop of Rome) asserted their spiritual authority as God’s representatives by opposing heretic and derivative faiths. They also enjoyed a large temporal power, thanks to the riches and organization of the Church. More or less successfully, the bishops and the clergy spread the Gospel, stimulated the reconstruction of towns (which over the long term meant the rebirth of commercial activities), tried to oppose violence, helped the poor and sick, and participated in political life by giving their support to the Germanic kings and warlords who became Christians (e. g. Clovis, later Pepin the Short, Charlemagne and Hugh Capet). The barbarian Germanic kings rapidly understood that nothing on an economic, political, social, or spiritual level could be done without the Church’s support, and most of them converted to Christianity.
In the troubled post-Roman time, amid the chaos resulting from the invasions, many Christians recoiled from the world and sought the isolation of religious communities, living as monks in monasteries under the authority of abbots. As early as 529, Benedict of Nurcia founded an abbey on Monte Cassino in Italy and created rules for observing vows of chastity, poverty and obedience with prayer and work. Monasteries multiplied and became spiritual and cultural nuclei in a world of disorder and violence.
Irish monks were particularly active in European evangelization in the 7th and 8th centuries, and after 663, Benedictine monks played an important role by giving Europe a united religion. However, theological disputes and political quarrels between the two great Christian poles, Rome and Constantinople, led to a schism in 1054. Christianity was then divided into two parts: the Roman Catholic Church under the authority of the pope in Rome, and the Greek Oriental Orthodox Church headed by the patriarch of Constantinople.
In spite of its severe faults, the Church prevented the disappearance of the Latin civilization and greatly participated in the creation of the medieval world and the rebirth of Europe.