The Human Terrain System (HTS) was catapulted into existence in 2006 by the US military’s urgent need for knowledge of the human dimension of the battlespace in Iraq and Afghanistan. Its centrepiece was embedded groups of mixed military and civilian personnel, known as Human Terrain Teams (HTTs), whose mission was to conduct social science research and analysis and to advise military commanders about the local population. Bringing social science — and actual social scientists — to the wars in Iraq and Afghanistan was bold and challenging. Despite the controversy over HTS among scholars, there is little good, reliable source material written by those with experience of HTS or about the actual work carried out by teams in theatre. This volume goes beyond the anecdotes, snippets and blogs to provide a comprehensive, objective and detailed view of HTS. The contributors put the program in historical context, discuss the obstacles it faced, analyse its successes, and detail the work of the teams downrange. Most importantly, they capture some of the diverse lived experience of HTS scholars and practitioners drawn from an eclectic array of the social sciences.