Over the previous decade, operations associated with irregular warfare have placed large demands on U.S. ground forces and have led to development of new Army and Joint doctrine. This report helps analysts identify and assess key factors that create and perpetuate environments susceptible to insurgency, terrorism, and other extremist violence and instability to inform military decisions on allocation of analytic and security assistance resources. The report focuses in particular on sources of understanding about these environments from the fields of sociology and cultural anthropology. RAND researchers surveyed existing sociological and anthropological theories and schools of thought and identified 12 key factors that give rise to and sustain unstable environments. The research found a relatively high degree of consensus among experts regarding the salience of these factors. The factors are interrelated and mutually dependent in complex ways. The report proposes a series of qualitative and quantitative metrics for each of the 12 factors and uses them in an analytic construct for assessing countries and regions based on their susceptibility to unstable environments.