"Arab civilization - that sounds like a good idea"

[anvi]

The Sunni-Shia split wasn't just about bickering over a successor to Muhammad, but also battles, in which Muhammad's grandson, whose family line Shias considered the rightful heirs to succession, was killed by the Sunni Umayyads. This event led to the formation of different collections and interpretations of the Hadith, the body of literature about Muhammad's religious practices, by Sunnis and Shias.  Subsequent battles between the factions ensued and have been intermittent in different regions in the history of Islam since, but there has also been social and political alliances between them.  I generally think the contemporary heated battles between the two factions have their roots in the threat that the Iranian revolution posed to the House of Saud, and the recent persecution of Sunnis by the predominantly Shia government in Iraq, where Shias themselves had been repressed for many decades before 2003, has only made things that much worse.  The common catchphrase about religious conflicts is that they go back "thousands of years" and such, but most modern friction between religious communities in the world is relatively historically new.