The interwar period marked a transition from a Gulf society characterized by symbiosis and interdependency to a sub-region characterized by national divisions, sectarian suspicions, rivalries and political tension. In this study, Chelsi Mueller tells the story of a formative period in the Gulf, examining the triangular relationship between Iran, Britain and the Gulf Arab shaykhdoms. By doing so Mueller reveals how the revival of Iranian national ambitions in the Gulf had a significant effect on the dense web of Arab-Iranian relations during the interwar period. Shedding new light on our current understanding of the present-day Arab-Iranian conflict, this study, which pays particular attention to Bahrain and the Trucial states (United Arab Emirates), fills a significant gap in the literature on the history of Arab-Iranian relations in the Gulf and Iran's Persian Gulf policy during the Reza Shah period.