Security sector reform (SSR) is central to the democratic transitions currently unfolding across the globe, as a diverse range of countries grapple with how to transform militias, tribal forces, and dominant military, police, and intelligence agencies into democratically controlled and accountable security services. SSR will be a key element in shifts from authoritarian to democratic rule for the foreseeable future, since abuse of the security sector is a central technique of autocratic government. This edited collection advances solutions through a selection of case studies from around the world that cover a wide range of contexts.