Tension between Middle Eastern regional powers Saudi Arabia and Iran are likely to intensify sectarian strains in countries that are home to both Sunni and Shiite Muslim communities. At the heart of the battle between Saudi Arabia and Iran is a four decade-old existential battle for dominance in the Muslim world. It is a battle that started with the 1979 Islamic revolution in Iran. Concerned that the Iranian revolution would offer a form of Islamic governance involving a degree of popular sovereignty that would challenge Saudi Arabia’s absolute monarchy that cloaks itself in a puritan interpretation of Islam, the kingdom went on the warpath. In doing so, it turned Wahhabi proselytisation into the single largest dedicated public diplomacy campaign in World War Two history, spending up to $100 billion since 1979 on the funding of Muslim cultural institutions across the globe and forging close ties to non-Wahhabi Muslim leaders and intelligence agencies.