How and why did Islamic civilization spread?

Islam is one of the four Abrahamic religions alongside Judaism, Christianity, and the Baha'i Faith. The followers of Islam are known as Muslims. Muslims believe that the prophet Muhammad received the word of Allah beginning in 610 AD. These teaching are compiled in the Quran, a holy text to all Muslims.

After Islam was established on the Arabian Peninsula in the 7th century A.D., it spread rapidly. Islam's expansion throughout the Middle East was due to the Umayyad Caliphate (661-750 AD), which conquered all of North Africa, most of modern Spain and Portugal, and Persia. In a caliphate, the government is run by a spiritual leader, someone seen as a successor to Muhammad. As these governments are based in Islamic teaching, converting conquered peoples is essential to the survival of the caliphate. During the time of the Umayyad Caliphate, non-Muslims were allowed to keep practicing their own religion as long as they paid a tax. Non-Muslims were also barred from holding high positions in the government.

In the Near and Far East, Islam spread through the exchange of ideas rather than military conquest. Traders on the Silk Road brought Islam into imperial China. By the 1600s mosques were common in western and central China. Despite foreign influence and China's Communist government, modern-day China is home to over twenty-three million Muslims, the majority of whom live in the western third of the country. Because of China's influence on the rest of Asia, Islam spread into Southeast Asia. For example, Indonesia is the world's most populous Muslim country.