On October 30, 2005, the Program on Humanitarian Policy and Conflict Research at Harvard University (HPCR) brought together a select group of international experts for a discussion on the theme of “The Transformation of Warfare, International Law, and the Role of Transnational Armed Groups.” The meeting was hosted by the Geneva Center for Security Policy in their offices in Geneva, Switzerland. This project grew out of a research interest identified at the High-Level Informal Expert Meeting on International Humanitarian Law at Harvard University in June 2004 which gathered representatives of twenty-eight governments and international organizations, as well as distinguished scholars, to examine the legal and policy challenges faced by international humanitarian law (IHL). The purpose of the meeting in Geneva was to explore the changed landscape of transnational wars and the prominent geopolitical role played by transnational non-state armed groups as well as their impact on interpretations and responses of international law to the new warfare. Built around three pillars of changing war, changing actors, and static law, the discussion in Geneva was organized along sessions on the transformation of war, the regulation of new conflicts, the current gaps and limitations of international humanitarian law, and the challenge of compliance and protection in the new environment. Starting from the decolonization wars of the twentieth century, armed conflicts have been departing gradually from the classical, state-centered paradigm embodied in the Geneva Convention of 1949 to the current framework in which non-state actors have acquired a larger, if not yet central, role. That fluctuation constitutes a bending of the traditional tactics of war brought about by the rise of comparatively weaker non-state actors and a modification in the space taken up by the new wars. Participants to the Geneva meeting stressed that non-state actors have been fighting states throughout the history of the state. However, in previous eras they fit more clearly into the realm of domestic law enforcement, as states sought to quell “internal disturbances.” The new conflicts are driven across state borders and represent a true challenge in terms of regulating the behaviors of both transnational non-state armed groups and the corresponding territorial and extraterritorial response of states.