The first caliph (632-634) and Muhammad's father-in-law.
Abu Bakr was an early convert to Islam and Muhammad's trusted advisor and close friend. Muhammad chose Abu Bakr to accompany him on his emigration to Medina in 622; Abu Bakr participated in all of Muhammad's expeditions and supported his decisions, however controversial. He was appointed to lead the pilgrimmage in 630 and to lead the prayers during Muhammad's last illness. After Muhammad's death, he was selected as the first caliph, though not without controversy. His two-year reign was marked by tribal rebellions and the expansion of the Muslim state into southern Syria and Iraq (see "The Four Righteous Caliphs").