More than a quarter of a century after his path-breaking Just and Unjust Wars, Walzer has updated the main themes of that work with a collection of essays. His line has always been to take just war theory seriously, as an alternative to absolutist pacifism or amoral realism. In 1977, with Vietnam still in mind, the arguments erred on the restrictive. Now, faced with wrongs that deserve to be righted-crude aggression, ethnic cleansing, mass terrorism-his arguments are more permissive. But much of the book is concerned with navigating through the dilemmas posed by any use of organized violence, however carefully applied or morally justified. Of particular importance is Walzer's identification of a new postbellum category that demands as much attention as the more familiar areas. Walzer writes with admirable clarity, elegance, and common sense. As military operations these days tend to be justified by reference as much to morality as to security, this rigorous framework becomes all the more valuable. This also means, however, that the dilemmas may be all the more acute, and the concluding series of short pieces on Iraq demonstrates just how difficult moral navigation can become.