There are many international relations theorists in academia who opine on world order and grand strategy. There are many policy analysts in think tanks with deep understanding of military programs, budgets, and operations. There are not many, however, who combine both sorts of expertise in equal depth. Barry Posen is one of the very best of the very few who do. Since the Cold War he has focused on clarifying the logic of choice among several models of American grand strategy in the context of practical considerations of cost.