Around A.D. 610, one man’s mystical experience in the Arabian Desert forever changed the world. In a cave outside Mecca, in what is now Saudi Arabia, a trader named Muhammad—a man known for his honesty and integrity—is said to have had a visit from the angel Gabriel. The angel told him he was to become a prophet and revealed the first few words of what would become the holy book of Islam, the Quran.

Muslims believe Muhammad was a descendant of Ishmael—Abraham’s first son by his wife’s maid, Hagar—forever linking Islam with Judaism and Christianity as one of the three, great monotheistic faiths.

Muhammad’s historical impact has been immense. His teachings, and the Islamic faith, have directly influenced social, political and religious institutions for 14 centuries.

Over those centuries, Islam spread out of Arabia, sweeping in three great arcs—one across North Africa and eventually into Spain, another north through the Middle East across Europe to the gates of Vienna, and the third east across Asia to the Pacific.

Islam’s theology of peace and submission to Allah produced civilizations of stunning beauty. But much of this expansion was the result of conquest, carried on swift horses by fierce warriors with the edge of the sword.

Islamic religious texts contain verses that supported this conquest and have a militancy that to this day extremists use to justify conquest, violence and acts of unspeakable terror—all in the name of Allah.

Today, Islam—little understood by most non-Muslims—is the faith of 1 billion people across the globe and the fastest growing religion in the world.