Mara E. Karlin in her book, Building Militaries in Fragile States: Challenges for the United States, investigates when, why and under what circumstances, US efforts to build partner militaries for internal defence succeeded and also offers some suggestions for improvement. The efforts examined include key decisions, programme execution and the nature of the US involvement with the partner state. She criticises US military interventions in what she calls ‘fragile states’ as unsustainable, thinly successful so far and fundamentally flawed. Karlin bases her observations on her investigation of the nature of the US interventions, as well as the role of unhelpful actors, by means of four case studies spanning Europe, Asia and the Middle East. These are: (a) Greece (from 1947); (b) South Vietnam (from 1954); (c) Lebanon I (from 1982); and (d) Lebanon II (from 2005). Karlin offers a compelling justification for the sampling methodology applied for selecting these four case units, given the significant number of militaries that the US has sought to build.