After billions of dollars and decades of investment in Afghanistan, Iraq and elsewhere, practitioners, policymakers and academics are still uncertain about which programs best foster stability in fragile and conflict-affected areas. This lack of clarity leaves decision makers without the information they need in order to select and support successful counterinsurgency, counterterrorism, and economic development goals. The political, social, and economic consequences of failing to learn from previous efforts are serious. Moreover, ongoing conflicts in Syria, West Africa and other parts of the world beg the question: what worked?