The authors describe why, despite an unprecedented commitment of resources, the UN Mission in Kosovo (UNMIK), supported militarily by NATO, has failed to achieve its goals. Their in-depth account is personal and passionate yet analytical and tightly argued. Both authors served with UNMIK and believe that the international community has a duty to intervene in regional conflicts, but they suggest that Kosovo reveals the difficult challenges inherent in such interventions. They also identify avoidable mistakes made at nearly every juncture by the UN and NATO.