The Byzantine Empire was centered around the eastern end of the Mediterranean between the Nile Valley and the Black Sea

The Byzantine Empire was centered around the eastern end of the Mediterranean between the Nile Valley and the Black Sea. Its territory included the remaining of eastern Roman Empire the fell in 450 AD. The government had a concern about how to maintain the empire using an army and an administration. The Christian Church was the solution as they had money through the system of tithes and had a sense of unity that helped expand the empire. Emperors based their ideas and claims of leadership on Roman Empire. On the other side, Islam started in Mecca and Medina by Muhammad in 610 A.D. after he experienced an angelic visitation. Muhammad made it his life mission to spread and teach what was dictated on the Qur’an. After his death, the Muslim community had no leader as Muhammed died without naming his successor. This is when caliphs were born, which were the leader of caliphates. Caliphates grew rapidly through conquest and used religion to further expand and govern (Jones).
Although the Islamic Caliphate and Byzantine Empire had substantially different legal systems, they were quite similar when using religion to govern during the post-classical period. Both empires appointed their religious leaders as the political leader, united people through religion to justify expansion, and gained public support for embracing religion which made it easier to govern.
To begin with, the Byzantine Empire and the Islamic Caliphates appointed their religious leaders as political leaders too. The Byzantine Empire used a system of Caesaropapism, where the Emperor is also the head of the Church, therefore, the state and church are intertwined (Jones). The church was viewed and treated as a department of state or as part of the government. The Byzantine government had a lot of control over the church. They chose the Patriarch of Constantinople which included bishops, priests, and patriarchs. These religious authorities had to give specific sermons which encourage Christians to follow and support the government (“Byzantine Religion”). For the Islamic Caliphates, their leader was called a caliph or “successor of Muhammad.” The caliph was in charge of the political and religious affairs, their duty was to maintain peace and uphold the law, and they had to be linked, by blood, to Mohammed’s Quraysh tribe. After Muhammad’s death, the only guidance he left were the laws of Islam itself, saying the religious and political aspects had to operate as one (Hays).
The Byzantine Empire and the Islamic Caliphates used religion to unite people and then expand their territories. After the eastern Roman Empire fell in 450 AD, the Byzantine Empire took that land under its power. Even though Rome, which was part of the Byzantine Empire, already practiced Christianity, the Byzantine Empire wanted to further expand their territory and eventually gain control of the land that the Western Roman Empire had lost before. (“Byzantine Religion” ). To do this, under Emperor Justinian they used Christian teachings to spread the faith and gain control of new territories. The Church had a lot of money and a sense of unity which helped the government in many ways. Leaders were able to mobilize armies to defend the religion which led to further expansion of territory.
Similarly, the Islamic caliphate used their beliefs and ideas to expand their territory. The Muslim army was quick and successful, which was the main reason they expanded. However, as the Arabs offered generous terms in return that Islam would be practiced on conquered places, their people were happy. The Islamic administration was simple and honest, something that was not common at the time. As people were tired of the corruption and persecution that happened in many empires, they preferred to join the Islamic Caliphate. Also, many passages from the Quran indicate how the military should act against non-muslims (“Early Rise Islam”).
The Islamic Caliphate followed the laws written in the Sharia Law. This law combines aspects from the Quran, Muhammad’s life and assorted legal precedents (Jones). Muslims followed these laws because they believed everything that was written in the Quran and Sharia was true and right. They also believed only God could make laws (Hays), therefore they can’t follow any laws coming from any human being or government with a democracy (Schirrmacher).
The Byzantine Empire based their laws on Roman Empire. had as they inherited part of Eastern Rome
They did make some changes but they were minimal.Byzantine reforms had political goals