History of Saudi Arabia
Uthman ibn Affan followed Umar as a caliph and ruled the longest of the four caliphs. In his twelve years of rule he standardized the Qur'an, spread the empire westwards to the Maghreb and even a part of Spain and eastward further into Central Asia. He was also assasinated which lead to Ali ibn Abi Talib being the fourth Sunni caliph and the first Shia imam.