By the middle of the 9th century Abbasid caliphs (king) started to lose control of the Islamic Empire. In some regions, local leaders recognized the caliph as a religious leader while choosing to govern themselves with their own set of rules. Gradually, the power base of the caliph began to erode. Then, in 969 the Fatimid Dynasty conquered Egypt and began construction on the city of Cairo. Cairo would become the new capital of the Islamic world. Under the rule of the Fatimid, Egypt prospered culturally and architecturally. The Fatimid constructed amazing mosques, palaces, and educational centers. Many of these buildings would survive long past the dynasty.
In 1171, Saladin or Salah al-din al-Ayyubi and his army overran Cairo with little opposition. Next, he swept through Egypt before defeating both Syria and Mesopotamia. Saladin believed he was unstoppable. Then in 1187, he fought against the Christian Crusaders, reestablishing Islamic rule over Jerusalem. The Islamic Empire was now broken into many parts, and most parts were controlled by men with military back grounds. Many of them were not interested in religion. At the same time, deep religious ideals now divided the Islamic community.
By the 13th century, Mongol armies were on the move. They swept through China and Russia, before finally invading Central Asia. Before long, the Mongols attacked Persia, overrunning Baghdad and the last remaining caliph. The Mongol invasions were devastating for Islam. Never again would one dynasty rule over Islam. Instead, three new powerful empires would eventually emerge.
The three empires were the Ottoman, the Safavid, and the Mughal. The Ottoman controlled most of the Middle East, Turkey, North Africa, and south-eastern Europe. At the same time, the Mughal dynasty ruled India, and the Safavid controlled Iran. In 1453, while under the leadership of Mehmet III, the Ottoman defeated Constantinople, and what remained of the Byzantine Empire, renaming the city Istanbul. The 15th through the 18th century were times of great prosperity under these three dynasties. The leaders of all three empires provided long periods of economic stability which resulted in tremendous prosperity. All of this created the perfect environment for Islam to spread into other regions.
The spread of Islam occurred on many levels. The fastest way was by conquering and converting. Most of Central Asia, Central Africa, and India was conquered and converted. Almost as soon as the country was conquered holy men, teachers, missionaries, and scholars began arriving. Eagerly they encourage people to convert. At the same time they were aided by Islamic merchants and soldiers who took it upon themselves to convert those who they had been defeated. Also, it was Islamic merchants who introduced the religion to East Africa, and the islands of Indonesia. Islam was firmly established in Africa and Asia by 1700. Today their exists a large Muslim population in India, China, and Pakistan. Today there are 35 million followers of Islam in China.