In 1999 three East-Central European states (Poland, Hungary, and the Czech Republic) gained membership in the North Atlantic Treaty Organization. Professor Barany argues that, once it began, the Alliance should continue the enlargement process. Nevertheless he maintains that only states that satisfy NATO's membership criteria should be allowed to join. Through an extensive analysis of four countries, Bulgaria, Romania, Slovakia, and Slovenia who, at the time of the book's original publication in 2003 were NATO aspirants, Barany demonstrates that they were in several important respects unprepared for membership and that there was no pressing reason for NATO's haste. Barany argues that while NATO should be clear that its doors remain open to qualified candidates, the Alliance should hold off further expansion until prospective members will become assets rather than liabilities.