When official representatives of more than 170 countries adopted the principle of the 'responsibility to protect' (R<inf>2</inf>P) at the September 2005 World Summit, Darfur was quickly identified as the test case for this new doctrine. The general verdict is that the international community has failed the test due to lack of political will. This article argues that the failure is real but that it is more fundamentally located within the doctrine of R <inf>2</inf>P itself. Fulfilling the aspiration of R<inf>2</inf>P demands an international protection capability that does not exist now and cannot be realistically expected. The critical weakness in R<inf>2</inf>P is that the 'responsibility to react' has been framed as coercive protection, which attempts to be a middle way between classic peacekeeping and outright military intervention that can be undertaken without the consent of the host government. Thus far, theoretical and practical attempts to create this intermediate space for coercive protection have failed to resolve basic strategic and operational issues. In addition, the very act of raising the prospect of external military intervention for human protection purposes changes and distorts the political process and can in fact make a resolution more difficult. Following an introductory section that provides background to the war in Darfur and international engagement, this article examines the debates over the R <inf>2</inf>P that swirled around the Darfur crisis and operational concepts developed for the African Union Mission in Sudan (AMIS) and its hybrid successor, the UN-African Union Mission in Darfur (UNAMID), especially during the Abuja peace negotiations. Three operational concepts are examined: ceasefire, disarmament and civilian protection. Unfortunately, the international policy priority o bringing UN troops to Darfur had an adverse impact on the Darfur peace talks without grappling with the central question of what international forces would do to resolve the crisis. Advocacy for the R <inf>2</inf>P set an unrealistic ideal which became the enemy of achievable goals. © 2007 Blackwell Publishing Ltd/The Royal Institute of International Affairs.