This cluster is designed to prepare PhD students for rigorous, policy-relevant research of the major threats to international and national security in the 21st century and the relevant forces that will confront those threats. Topics of study will include terrorism; proliferation of weapons of mass destruction; rapid shifts in regional and global distributions of capabilities; insurgency, civil war, and regional political instability; military force composition and capability; civil-military relations; and new innovations in military technologies. The Cluster will combine social science training in international security politics and national defense policy, focused study of specific regions of the world, and exploration of the technical and scientific aspects of proliferation, weapons innovations, terrorist and counter-terrorist operations, and insurgency and counterinsurgency warfare.