<P> As of January 2011, there were 1.62 billion Muslims, with one out of five people in the world being Muslim, making Islam the second - largest religion in the world . </P> <P> The expansion of the Arab Empire in the first centuries after Muhammad's death soon established Muslim dynasties in North Africa, West Africa, to the Middle East, and Somalia . </P> <P> Within the century of the establishment of Islam upon the Arabian peninsula and the subsequent rapid expansion of the Arab Empire during the Muslim conquests, one of the most significant empires in world history was formed . 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 . </P> <P> 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 native Christians and Jews who existed peacefully before the Muslim invaders arrived . </P>

What type of geographic locations did the islamic empire settle in