Rashidun Caliphate Founded

In 632 AD, after the death of the Prophet Muhammad in Medina, the Muslim community chose Abu Bakr as its leader, creating the office of caliph (from the Arabic khalifa, meaning "successor" or "deputy"). The decision settled an immediate crisis of succession and began the Rashidun Caliphate, the first of the Islamic caliphates. Over the next three decades it grew from a polity centered on western Arabia into a state that stretched across much of the Middle East, and it shaped the political and religious identity of the Islamic world.

Muhammad had united much of Arabia under his leadership, but he left no clear, universally accepted arrangement for what would follow him. While his family and close companions were preparing his burial, a group of Medina's Ansar (the "helpers") gathered to discuss choosing their own leader. Abu Bakr, one of Muhammad's earliest followers and closest companions, and a few other senior figures came to the gathering, and Abu Bakr was given the community's allegiance. Later Sunni tradition regards this as a legitimate consultative choice. Some of Muhammad's supporters, who became the core of Shia Islam, held that his cousin and son-in-law Ali ibn Abi Talib had the stronger claim. This disagreement would deepen into one of Islam's lasting divisions.

Abu Bakr's brief reign, which lasted about two years, was dominated by the Ridda wars, or "wars of apostasy." Several Arabian tribes rejected the authority of Medina, refusing to pay the alms tax or following rival prophets. Through military campaigns, Abu Bakr reasserted control over the peninsula. Commanders such as Khalid ibn al-Walid played a prominent role. Once Arabia was secured, raids began toward the territories of the Byzantine and Sasanian empires.

The expansion accelerated under his successors Umar, Uthman, and Ali. Within a few decades, Muslim armies had conquered Syria, Egypt, and Iraq, and brought down the Sasanian Empire in Persia. Both great powers had been weakened by decades of mutual warfare, which helped the campaigns succeed, though historians continue to debate the relative weight of this exhaustion, military organization, and religious motivation. Garrison cities such as Basra and Kufa were founded, and early administrative systems took shape, often drawing on existing Byzantine and Persian practices.

The Rashidun period ended in 661 after a series of internal conflicts. Uthman was assassinated, and Ali's caliphate was torn by the first civil war, or fitna. Ali was himself murdered, and Mu'awiya established the Umayyad dynasty. Later Sunni Muslims remembered the first four caliphs as the "rightly guided" ones, an idealized model of leadership, while the memory of their disputes continued to inform Islamic politics and theology.