Umar
Under Umar, the caliphate expanded. It ruled the Sasanian Empire and more than two-thirds of the Byzantine Empire. His attacks on the Sasanian Empire resulted in the conquest of Persia in less than two years. Jewish tradition says that Umar set aside the Christian ban on Jews and let them into Jerusalem and to worship. Umar was assassinated by the Persian slave Abu Lu'lu'a Firuz in November 644.