Because terrorist groups are highly fragmented, actions against terrorism, although individually of high quality, may be inefficiently targeted, uncoordinated and compartmentalized, or ineffective. This paper suggests a conceptual framework, the conjunction of terrorist opportunity (CTO) which could help join up the domestic and international responses to terrorism, and complement the more common top-down analyses. CTO potentially allows each family of causes of terrorism to be tackled by an equivalent family of intervention principles, using clearly specified and targeted methods. The paper begins by setting out the 11 immediate causes of CTO which can be considered the necessary micro-components which must come together for the terrorist event to happen. Prior causes are listed which are needed to understand and prevent terrorist events. Lastly, analyzing the causes suggests how a suite of actions can then be chosen to match terrorist problem and context and to reflect tactical and strategic priorities; geographic scales; and the capabilities of the preventing agency. This analysis focuses mainly on international, networked, or franchised terrorism rather than state-sponsored terrorism. The overall analysis is intended to facilitate reduction of the risks and seriousness of those events, and the wider climate of terror which they create. Appendix, 44 notes