Beginning with the 2003 invasion of Iraq and concluding with the aftermath of the 2011 Arab uprisings, Frederic M. Wehrey investigates the roots of the Shi?a-Sunni divide now dominating the Persian Gulf's political landscape. Focusing on three Gulf states affected most by sectarian tensions--Bahrain, Saudi Arabia, and Kuwait--Wehrey identifies the factors that have exacerbated or tempered sectarianism, including domestic political institutions, the media, clerical establishments, and the contagion effect of external regional events, such as the Iraq war, the 2006 Lebanon conflict, the Arab uprisings, and Syria's civil war.