Despite the handwringing and promises of never again, the grim recurrences of genocide and crimes against humanity around the world have made it emphatically clear that the international community has been largely ineffective in stopping mass atrocity crimes. Drawing on candid interviews with eighty key figures involved in American and Canadian responses to the Rwandan genocide of 1994 and the Kosovo crisis of 1999, Mobilizing the Will to Intervene explains why and provides a roadmap for change.