The ‘war on terror’, launched by the US government and its allies in the wake of the September 11, 2001 attacks in New York and Washington, has profoundly transformed the geopolitical environment of the past decade. In particular, the dominance of hard security approaches to inter- and intra-state conflicts has led to a generalised interpretation of all forms of armed insurgencies that challenge the established socio-political order being seen through the lens of ‘terrorism’, regardless of the nature of such actors, their degree of social legitimacy or their political roles and aspirations. Such trends have severely affected not only the dynamics of armed conflicts, but also the course of peace processes and post-war environments. There has indeed been an increasing tendency to view all armed actors as ‘spoilers’ to be fought at all costs or, at best, pacified through disarmament, demobilisation and reintegration (DDR), rather than as agents of change who can play constructive roles in securing peace and building more legitimate states. Against this background, the purpose of this report is to present key policy-relevant findings from a two-year participatory research project on the timing, sequencing and components of post-war security transitions, from the perspective and self-analysis of conflict stakeholders who have made the shift from being state challengers to being peace- and state-building agents in South Africa, Colombia, El Salvador, Northern Ireland, Kosovo, Burundi, Southern Sudan, Nepal and Aceh. Unless otherwise stated, the empirical data presented here is based on thematic case studies, which were written by local teams made up of researchers and former combatants, and which were collected and analysed in an edited volume published in parallel with this report (Dudouet, Giessmann and Planta 2012). Any unattributed citations stem from the book. There is increasing acknowledgement within the peacebuilding policy and research communities that DDR and security sector reform (SSR) are mutually dependent and are in turn heavily conditioned by their broader political environment. Building on this, the project sought to address the conditions under which armed resistance/liberation movements (RLMs) generate and maintain the political will to restore the state’s monopoly over the use of force and participate in post-war peacebuilding. It does so by assessing the interconnections between individual, organisational and structural transitions in the spheres of security and political governance. This report presents the main conclusions of this research process, as well as their implications for international efforts to support inclusive, participatory, holistic and sustainable post-war transitions. It focuses less on the negotiation of peace agreements – which was addressed more specifically in previous reports (Dudouet 2008, 2009) – than on the factors conducive to their effective implementation. Drawing comparative lessons from nine cases of successful war-to-peace transitions, it aims to identify common findings that can be generalised to various types of intra-state armed conflicts and post-war contexts. At the same time, it also presents context-specific findings for particular situations such as security transitions amidst an ongoing conflict (Colombia) or in contexts of state formation (Southern Sudan, Kosovo). The report is organised as follows: after compiling the main policy recommendations resulting from the analysis, it presents the research background, some key definitions and the core problems at stake. It then spells out thematic challenges, lessons learnt and policy recommendations (highlighted in boxes) for managing volatile post-war transitions and building more legitimate, democratic and accountable political and security institutions