This is a useful, authoritative little book by one of the leading experts on the theory and practice of humanitarian intervention. This topic was on the crest of a wave at the turn of the century, culminating in the publication of a major report on "the responsibility to protect," for which Weiss was the research director. This report sought to establish a norm for states to meddle in other states when they were palpably failing to look after their own citizens. It came out just after 9/11, and the interventions that followed that event were more ambitious than argued for and not undertaken for purely humanitarian reasons. For the purists, this was unfortunate, for it both gave intervention a bad name and created a degree of fatigue, even when disasters such as that in Darfur demanded attention. Weiss believes in the responsibility to protect and can point to real successes, as well as tragedies, such as in Rwanda, where nothing was done. As he reviews the case studies and the disarray of the humanitarian agencies, Weiss appears to be struggling to sustain optimism for the future.