After the assassination of the third Caliph, Uthman ibn Affan, the Sahabah (Companions of Muhammad) in Medina selected Ali to be the new Caliph. He encountered defiance and civil war (First Fitna) during his reign. Tragically, while Ali was praying and bowing to God in the Great Mosque of Kufa, Abd-al-Rahman ibn Muljam, a Kharijite assassin, struck him with a poison-coated sword.