Security sector reform (SSR) is widely recognized as key to conflict prevention, peace-building, sustainable development, and democratization. SSR has gained most practical relevance in the context of post-conflict reconstruction of so-called "failed states'" and states emerging from violent internal or inter-state conflict. As this volume shows, almost all states need to reform their security sectors to a greater or lesser extent, according to the specific security, political and socio-economic contexts, as well as in response to the new security challenges resulting from globalization and post-9/11 developments. Alan Bryden is a researcher at the Geneva Centre for the Democratic Control of Armed Forces. Heiner Hnggi is assistant director of the Geneva Centre for the Democratic Control of Armed Forces.