Combating Islamist terrorism has been at the top of the US national security agenda for nearly two decades. The campaign against groups like al-Qaeda and the Islamic State (and their purported allies in places like Afghanistan) continue to consume vast national security resources. What was once known as the ‘global war on terrorism’ has become a global war with no name – and with no end in sight. This chapter offers an assessment of one aspect of that campaign, namely the effort to ‘disrupt, dismantle, and defeat’ al-Qaeda. It draws on a congressionally mandated study commissioned in 2017 by the Assistant Secretary of Defense for Special Operations and low-intensity conflict. That qualitative assessment, which covered the 2001–16 period, employed a variety of approaches and techniques, including the creation and comparative analysis of case studies; analyses of security conditions in regions where al-Qaeda operates; and the creation of an inventory of US-led (and US supported) operations and programs. Sources for the assessment included strategic-level US policy documents, operational and tactical reports; structured discussion with senior civilian and military leaders, as well as retired officials and military officers; and open-source material, including social media.