The decision to expand NATO eastward is a fateful venture that has received surprisingly little public attention. Advocates of enlargement insist that the step will foster cooperation, consolidate democracy, and promote stability throughout Europe. But the contributors to this volume conclude that an expanded NATO is a dubious, potentially disastrous idea. Instead of healing the wounds of the Cold War, it threatens to create a new division of Europe and undermine friendly relations with Russia. Even worse, it will establish expensive, dangerous, and probably unsustainable security obligations for the United States.