This paper examines the interaction between US grand strategy and the threat of terrorism posed by the al-Qa’ida network over thirteen years following 9/11. It focuses analysis on the question: to what extent has terrorism affected US grand strategy since 9/11? Utilizing Barry R. Posen’s conception of grand strategy it contends that all four post-Cold War administrations’ have pursued a grand strategy of primacy through US global leadership—albeit to varying degrees of intensity. Furthermore, it argues that the continued threat of terrorism since 9/11 has caused a demonstrable shift in the context in which the objectives of this grand strategy have been pursued. It has changed from a predominately peacetime context where the exploitation of US primacy and the expansion of the liberal democratic international order were relatively easy, to a predominately wartime context where it has become increasingly costly and difficult in an era of persistent conflict.