Islam's Expansion

How was it possible for Islam to expand so rapidly after its founding in the hostile environment of the Arabian Peninsula in the early 7th century? Compare the military, political, and religious policies of the early caliphs, the Umayyad dynasty, and the Abbasid dynasty, and their respective contributions to the expansion of Islam as a political, religious, and cultural force. How would you account for the religious conversion of regions beyond the military reach of the expanding Islamic states of Southwest Asia and Northern Africa to Islam, such as West Africa of Southeast Asian? What key roles did Islam play in cultural and economic exchanges?