Due to the struggle of supremacy during 5th-7th century, three heirs developed from the Roman Empire. The three descendants of Roman Empire which included Western Europe, byzantine, and Islamic society after the separation developed with distinctive religion, culture, and language. Due to fight for power, these heirs became rivals within a short period of time.
Byzantium civilization which occurred in 5th century emerged from the Eastern half of Romans Empire. It was facilitated by Constantinople capital that supported them economically; this flow of money enabled them to look for slaves that helped them to fight for power. Their success was a combination of the traditional governments of Roman Imperial with pursuit of the orthodox form of Christian faith. The orthodox religion moved to Eastern Europe and Russia at the time of Appanage and Kevin Rus which occurred in 1054AD-1480AD and 882AD-1240AD respectively (Avni 400).
Islamic civilization and development occurred around 7th century. It was formed by Mohammed who was understood to be the leader and the prophet of this group (Avni 700). This group spoke Arabic language. Their stability was facilitated by the government and culture which supported this vibrant group. Their empire was created in the Old Near East, around the cost of Mediterranean and moved into the subcontinent of India. The Islamic culture was so strong that it mobilized most people along the Mediterranean cost facilitating the stability of this group.
Western Europe which was formed around 6th century had different languages depending on the education level. Clergy people who were educated spoke Latin language while Laity people spoke mostly in vernacular languages (Avni 506). Their civilization was slow as compared to Byzantium and Islamic since their government economy and structure were weak. Later, it shifted towards religious and political cohesiveness based on Christianity. Through Christian religion, it emerged expansionistic, creative, and dynamic during middle ages.
Avni, Gideon. The Byzantine-Islamic Transition In Palestine: An Archaeological Approach. New York, NY: Oxford University Press, 2014. Discovery eBooks