On September 24, 622, the prophet Muhammad completes his Hegira, or “flight,” from Mecca to Medina to escape persecution. In Medina, Muhammad set about building the followers of his religion—Islam—into an organized community and Arabian power. The Hegira would later mark the beginning (year 1) of the Muslim calendar.
Muhammad, one of the most influential religious and political leaders in history, was born in Mecca around 570. His father died before he was born, and Muhammad was put under the care of his grandfather, head of the prestigious Hashim clan. His mother died when he was six, and his grandfather when he was eight, leaving him under the care of his uncle Abu Talib, the new head of the clan. When he was 25, Muhammad married a wealthy widow 15 years his senior. He lived the next 15 years as a merchant, and his wife gave birth to six children: two sons, who died in childhood, and four daughters.
From time to time, Muhammad spent nights in a cave in Mount Hira north of Mecca, ruminating on the social ills of the city. Around 610, he had a vision in the cave in which he heard the voice of a majestic being, later identified as the angel Gabriel, say to him, “You are the Messenger of God.” Thus began a lifetime of religious revelations, which he and others collected as the Qur’an, or Koran. Muhammad regarded himself as the last prophet of the Judaic-Christian tradition, and he adopted aspects of these older religions’ theologies while introducing new doctrines. Muhammad’s monotheistic religion came to be called Islam, meaning “surrender [to God],” and its followers were Muslims, meaning “those who have surrendered.” His inspired teachings would bring unity to the Arabian peninsula, an event that had sweeping consequences for the rest of the world.

By 615, Muhammad had gained about 100 converts in Mecca. He spoke out against rich merchants, who he criticized as immoral in their greed, and he denounced the worshipping of idols and multiple gods, saying, “There is no god but God.” City leaders became hostile to him, and in 619 his uncle Abu Talib died and was succeeded as head of the Hashim clan by another one of Muhammad’s uncles, Abu Lahib. Abu Lahib refused to protect Muhammad, and persecution of the prophet and his Muslims increased.
In the summer of 621, an entourage of 12 men came to Mecca from Medina, an oasis community 200 miles to the north. They were ostensibly making a pilgrimage to Mecca’s pagan shrines, but they had actually come to meet with Muhammad and profess themselves as Muslims. In 622, a larger group of converts from Medina came to Mecca and took an oath to Muhammad to defend him as their own kin. Muhammad immediately encouraged his Meccan followers to make their way to Medina in small groups. When city authorities learned that the Muslims had begun an exodus, they plotted to have the prophet killed. Under this threat, Muhammad slipped away unnoticed with a chief disciple and made his way to Medina, using unfrequented paths. He completed the celebrated Hegira (Hijrah in uncorrupted Arabic) on September 24, 622. The history of Islam had begun.
At Medina, Muhammad built a theocratic state and led raids on trading caravans from Mecca. Attempts by Meccan armies to defeat the Muslim forces failed, and several leading Meccans immigrated to Medina and became Muslims. Muhammad later become more conciliatory to Mecca, and in 629 he was allowed to lead a pilgrimage there in exchange for a peace treaty. Shortly after, he was attacked by allies of the Meccans, and Muhammad denounced the treaty. In January 630, he returned to his birthplace with 10,000 men, and the Meccans swore allegiance to its Muslim conquerors. He was now the strongest man in Arabia. During the next few years, most of the peninsula’s disparate Arab tribes came to him to ask for alliance and to convert to his religion. By his death, on June 8, 632, Muhammad was the effective ruler of most of Arabia, and his rapidly growing empire was poised for expansion into Syria and Iraq.

Within 20 years, the Byzantine and Persian empires had fallen to the prophet’s successors, and during the next two centuries vast Arab conquests continued. The Islamic empire grew into one of the largest the world has ever seen, stretching from India, across the Middle East and Africa, and up through Western Europe’s Iberian peninsula. The spread of Islam continued after the fragmentation of the Arab empire, and many societies in Africa and Asia voluntarily adopted Muhammad’s religion. Today, Islam is the world’s second-largest religion.