Islam and Christianity emerged from the same cultural and geographic setting in Western Asia, which is better known as the Middle East, and drew from this region’s ancient traditions and more specifically from Judaism and the Jewish people. Christianity emerged first and was inspired by the death and life of Jesus Christ of Nazareth, whose death became a mythic center f this religion as symbolized by a belief in eternal life. Islam emerged approximately five hundred years later and was founded by Prophet Mohammed, although this religion also considered Jesus as a prophet with Mohammad considered as God’s ultimate prophet. Following the inception of Islam, most Muslims considered their faith as a continuation of Christianity and Judaism. Indeed, the Qur’an identifies numerous prophets from the Hebrew Bible although Mohammad was identified as the last of the long prophetic line. Muhammad was considered the most important prophet in Islam followed by Jesus. Theological differences, however, were identified early on in the development of Islam and have continued across history and pose significant challenges to relationships between the two faiths.

There are several factors that explain the universal and accessible appeal of early Islam. To begin with, the Greek Byzantine and Persian Sassanian Empires became exhausted following years of struggle, enabling Islam to occupy a power vacuum as it spread across Western Asia. Further, the Pact of Umar placed significant restrictions on non-Muslims, but did not force non-Muslims to convert to Islam, instead giving them ‘dhimmi’ status where they were required to pay poll taxes for protection. Therefore, there was little resistance to the spread of Islam from Christian communities as they retained a right to govern their communities and practice their religion. Another aspect that made Islam universally accessible was the work of Avicenna, whose work as a philosopher spread across Western Asia and medieval Europe and also allowed for the spread of Islam. His metaphysics formed the foundation of philosophical theology and Islamic philosophy, greatly influencing the people living in these regions and making Islamic thought appealing to these populations. Moreover, the Christian church had gone through significant divisions into five main apostolic sets in Alexandria, Jerusalem, Constantinople, Antioch, and Rome. These divisions made Islam appealing to many oriental Christians who welcomed the political authority in Islam as a relief from the more fragmented Byzantine oversight, enhancing their cooperation with Muslim rulers.

On the other hand, Christianity also had universal and accessible appeal for several reasons. Perhaps the most important factor that increased the appeal of medieval Christianity was that this religion created new communities, especially in a community where there was significant inequality and poverty. Indeed, the Romans reinforced inequality though the Augustan system which was hierarchical and considered the emperor as the conduit between the people and the divine world. The new community that appealed to medieval Christians specified that Christ was neither free nor a slave, neither female nor male, and neither Greek nor Jew; which was the definition of a new community that promised equality in a feudal system. By giving the lowliest persons in medieval Europe status and dignity, Christianity was considered a universal religion that enhanced equality for members of communities across the continent. Moreover, medieval Christianity was also appealing because of its commandment of love, which was decisive and provided these individuals with care from other members of the community. By taking the people out of the isolation that characterized medieval Europe, Christianity was appealing to most poor people and helped them to form communities.

However, various events that occurred following the rise of Islam led to angry and bitter divisions between Islam and Christianity. To begin with, the ill treatment and prejudices against minorities by both Christians and Muslims became a major characteristic of the relationship between both religions. For instance, by the 10 AD, hostilities characterized the relationship between Christians and Muslims in the Iberian Peninsula particularly between the northern Kingdom of Leon and the southern al-Andalus region that were populated by Christians and Muslims respectively. The Crusades, which took place over centuries, left most Muslims and Christians bitter especially with regard to the issue of Jerusalem’s sovereignty. The Siege of Antioch represented the first crusade and ended in victory for the Christians against Muslim rulers, although it only served to exacerbate the feelings of ill-will from h mainly Muslim peasants. The siege of Antioch was a significant turning point in the war between Islam and Christianity, showing the latter to have a stronger force that could besiege and force the surrender of a large city protected by a larger army. However, the disunity among the ranks of its Muslim defenders was the main cause of its collapse, and this led to resentment from Muslim peasants who felt he Christians were dividing and destroying Islam.

Another event that evidences the new divisions introduced by Christianity and Islam was the conquest of Constantinople. Divisions between followers of Islam and Christianity became particularly intense towards the end of the middle ages, with the fall of Constantinople and the subsequent expulsion of Muslims from Andalusia illustrating the significant divisions between both religions. Since Constantinople had stood as the Byzantine Empire’s capital for more than ten centuries, its fall to the Muslims was a significant shift in Christian-Islam power relations and raised the specter Europe being taken over by Muslims. In turn, Christians in Europe became more wary and distrustful of Muslims and this development was directly responsible for the brutal and effective expulsion of Muslims from the Iberian Peninsula. The conquest of Constantinople was a massive blow to Christianity as the Muslim armies led by the Ottoman Empire could now advance into Europe without worrying about adversaries attacking them from the rear.