After the Holocaust, the world vowed it would never again stand by and permit such heinous crimes against humanity. Yet many subsequent atrocities have gone unchecked, all over the world: from the killing fields of Cambodia, to Rwanda, and to Srebrenica. The bloody list continues to grow, led by the unfolding nightmare in Darfur. How and why were the world's best intentions derailed, and what can be done today to put these efforts back on track? The "responsibility to protect: - R2P for short - was unanimously embraced at the UN World Summit in 2005. The heart of this new international norm is the belief that if sovereign governments fail to protect their own people from mass atrocity crimes, then responsibility shifts to the wider international community to take whatever action is appropriate, including (in extreme cases) the use of force. The world cannot, and will not, just stand by. Evens spells out the steps needed to make R2P work in practice and clarifies the misunderstandings, real or contrived, which persist about its scope and limits. He emphasizes the need for preventive action, and for preferring assistance and persuasion to coercion, but he also makes clear when it is right to fight. The book is enlivened throughout by real world examples, analyses of current events, and assessments drawn from the author's own vast experience.