An interesting mix of political science and history by a wise student of strategic affairs, this book covers the brief period of the American nuclear monopoly, from 1945 to 1949. The author has no hesitations about exploring counterfactual scenarios and indeed is very good at it. Could the United States have engaged in preventive war? Was the H-bomb necessary? Could the United States have extracted more political mileage out of its window of strength? One might not think playfulness a virtue in matters nuclear, but this book suggests otherwise-and it reminds us that history took only one of an infinite number of possible paths.