Increasing conversion to Islam paralleled the rapid military expansion of the Arab Empire in the first centuries after the Islamic prophet Muhammad's death. Muslim dynasties were soon established in North Africa, West Africa, throughout the Middle East and in Iran. It is generally agreed upon by historians that this took place through conversion of slaves and poor people, as well as waging wars on nearby tribes.
 Phase I: The Early Caliphs and Umayyads (610-750)
See also: Muslim conquests, Rashidun Caliphate, and Umayyad Caliphate This was the time of the life of Islamic Prophet Muhammad and his early successors, the four rightly guided caliphs, as well as the dynasty of the Umayyad Caliphs (661-750). In the first last century the establishment of Islam upon the Arabian peninsula and the subsequent rapid expansion of the Arab Empire during the Muslim conquests, resulted in the formation of an empire surpassed by none before. For the subjects of this new empire, formerly subjects of the greatly reduced Byzantine, and obliterated Sassanid, Empires, not much changed in practice. The objective of the conquests was more than anything of a practical nature, as fertile land and water were scarce in the Arabian peninsula. A real Islamization therefore only came about in the subsequent centuries. Ira Lapidus distinguishes between two separate strands of converts of the time: one is animists and polytheists of tribal societies of the Arabian peninsula and the Fertile crescent; the other one is the monotheistic populations of the Middle Eastern agrarian and urbanized societies. For the polytheistic and pagan societies, apart from the religious and spiritual reasons each individual may have had, conversion to Islam "represented the response of a tribal, pastoral population to the need for a larger framework for political and economic integration, a more stable state, and a more imaginative and encompassing moral vision to cope with the problems of a tumultuous society." In contrast, for sedentary and often already monotheistic societies, "Islam was substituted for a Byzantine or Sassanian political identity and for a Christian, Jewish or Zoroastrian religious affiliation." Conversion initially was neither required nor necessarily wished for: "(The Arab conquerors) did not require the conversion as much as the subordination of non-Muslim peoples. At the outset, they were hostile to conversions because new Muslims diluted the economic and status advantages of the Arabs." Only in subsequent centuries, with the development of the religious doctrine of Islam and with that the understanding of the Muslim ummah, did mass conversion take place. The new understanding by the religious and political leadership in many cases led to a weakening or breakdown...