Terrorism, like war, never ends; but individual terrorist campaigns and the groups that perpetuate them always do. Why? This Adelphi Paper comparatively examines the waning days of terrorist groups, to understand crucial points where a critical mass of factors developed and led toward their demise. The goal is to identify typical watersheds and mistakes and search for parallels with the current threat. Like all other terrorist movements, al-Qaeda will end.While it is a remarkable movement with traits that exploit and reflect the current international context, it is not utterly without precedent: some aspects of al-Qaeda are unusual, but some are not. How terrorist movements end reflects, among other factors, the counter-terrorist policies taken against them. It therefore makes sense to formulate those policies with an awareness of historical precedents and a specific image of an end in mind. The monograph analyses recent experience with the decline and demise of terrorist groups to gather policy lessons that apply to domestic, foreign and security policy today.