The spread of Islam started shortly after the death of the Islamic prophet Muhammad in 632 AD. During his lifetime, the community of Muhammad, the ummah, was established in the Arabian Peninsula by means of conversion to Islam and conquering of territory, and oftentimes the conquered had to either accept Islam or pay tax (jizyah) for protection if they chose to not convert. Among others, the tax permitted the non-Muslim citizens to practice their faith, and ensure protection from outside aggressors. In the first centuries conversion to Islam followed the rapid growth of the Islamic world under the Rashidun and Umayyad Caliphs.
Muslim dynasties were soon established and subsequent empires such as those of the Abbasids, Fatimids, Almoravids, Seljuk Turks, Mughals in India and Safavids in Persia and Ottomans were among the largest and most powerful in the world. The Islamic world was composed of numerous sophisticated centers of culture and science with far-reaching mercantile networks, travelers, scientists, hunters, mathematicians, doctors and philosophers, all of whom contributed to the Golden Age of Islam.
The activities of this quasi-political early ummah resulted in the spread of Islam as far from Mecca as China and Indonesia, the latter containing the world's largest Muslim population. As of October 2009, there were 1.571 billion Muslims,[1] making Islam the second-largest religion in the world.[2]

THE EXTRAORDINARY SPREAD OF ISLAM AND ITS MAIN DYNAMICS
Islam, in the tenth century, was the main religion, or at least, the religion of the majority of peoples in an area covering more than half of the civilized world stretching over three continents from the Pyrenees and Siberia in West and North Europe to the farthest end of Asia, up to China and New Guinea in the East; from Morocco in North Africa to the southern tip of Africa, covering two-thirds of the