Since 2001, successive U.S. administrations have increasingly prioritized efforts to build foreign security forces -- particularly in weak and failing states -- arguing that doing so advances U.S. national security objectives. In turn, the Department of Defense (DOD) has invested billions of dollars in "Building Partner Capacity," (BPC) a term that refers to a broad set of missions, programs, activities, and authorities intended to improve the ability of other nations to achieve those security-oriented goals they share with the United States. This book first seeks to build a common understanding of what, exactly, constitutes BPC by illuminating the various ways in which different USG components define it. In so doing, it charts the evolution of BPC in national strategy documents since the term was first coined in 2006. With that intellectual baseline established, it then explores whether BPC has proven an effective means by which the United States has accomplished its strategic objectives to which such programs have directed since World War II. Moreover, the book discusses Section 1206 of the National Defense Authorization Act (NDAA), which provides the Secretary of Defense with authority to train and equip foreign military forces for two specified purposescounterterrorism and stability operationsand foreign security forces for counterterrorism operations. The book also provides basic information on the Global Security Contingency Fund (GSCF) legislation; describes processes State and DOD have developed to manage the program; describes the status of GSCF projects; and assesses the extent to which State and DOD have clearly defined time frames for GSCF projects.