The Rashidun Caliphs, Early Conquests, and the Sunni-Shia Schism

The first four caliphs who governed the Muslim community between 632 and 661 are known in Sunni tradition as the Rashidun, the "rightly guided." Abu Bakr (632-634) devoted his brief rule to suppressing the Ridda wars, a wave of tribal rebellion that broke out across Arabia after Muhammad's death, as numerous tribes considered their allegiance to have been personal to the Prophet and refused to keep paying the religious tax, zakat, to Medina; the general Khalid ibn al-Walid crushed the rebellion, most decisively at the Battle of Yamama, restoring the political unity of Arabia under Medina by around 633.