For the most part this book is not about the transformation of U.S. security since the collapse of the Soviet Union. Rather it is a rigorous study of the security challenge that the Soviet Union would have posed for the United States had it held together and remained under the liberalizing influence of Mikhail Gorbachev. Two concluding chapters partly depart from this approach. In one, Charles Glaser and Ted Hopf draw lessons from the changing U.S.-Soviet relationship for U.S.-Russian relations; in the other, Paul Huth assesses the theoretical discussion underway among American academics over the implications for European security of the disintegrated Soviet empire. This is not the place to come if one is looking for policy guidance in dealing with the morass of new post-Soviet states now entering international politics. But it most definitely is if one wants to think more systematically about the changes in international politics occurring immediately beforehand, particularly as influenced by shifts in Soviet foreign policy.