This article examines the impact of the doctrine of the Responsibility to Protect on Peacekeeping in the United Nations. One of the key debates in peacekeeping is whether there is a duty to use force to protect civilians from genocide, crimes against humanity and war crimes. The practice of UN peacekeeping is evolving in many instances, with the notable exception of Darfur, into robust peacemaking actions with a positive responsibility to protect civilians within the field of operations. This article reviews the development of the concept of the responsibility to protect and then applies the various parts of the doctrine to actual situations of threats to international peace and security.