In many areas of limited statehood, states fail to provide security and protection to their citizens. International actors dedicate increasing resources to the reform or reconstruction of effective and legitimate security architectures in these places. Examples are Liberia after a devastating 14-year civil war ended in 2003; Timor Leste following the referendum for independence in 1999; and the Palestinian Territories in the context of the on-going Middle East peace process. The C6 research project explores the role of international actors in rebuilding and reforming security structures in areas of limited statehood, and assesses the consequences of these efforts. Our research encompasses the activities of core actors such as the United Nations, the European Union, and relevant donor states in international state-building, along with security sector reform missions in Liberia, Timor Leste and the Palestinian Territories. We aim to answer the following questions: What conditions are most important in determining the output of these security efforts? Why do initiatives so frequently fail or lead to only fragmentary and incoherent reforms? How do transferred security institutions interact with local security structures?