Since the fall of the Berlin wall, the two sides of the Atlantic have struggled to identify a new common project and create the tools and institutions needed to address common challenges. To their credit, they have transformed their militaries, integrated new members into Western institutions such as the European Union and NATO, deepened economic ties, developed new partnerships, and acquired new capabilities. But they have also had a number of ugly and public disputes over the nature and severity of the threats they face as well as the means necessary to combat such threats. Now, several years after the dark days of 2002 and 2003, the transatlantic partners are working toward renewal. Although Iraq remains a stain on their relationship, Europe and the United States have come to realize that, however vast their differences might be, they remain indispensible partners to each other. The question before the two partners today, particularly in light of the change in administration in Washington, is how to capitalize on their comparative strengths to address a long list of common challenges--one of the most pressing of which is nuclear proliferation. In an effort to shed light on the issues, CSIS commissioned a series of essays on European perspectives on nonproliferation. This new report offers a starting point for a new, shared understanding of the threat. It begins not with a look at the official positions of states with regard to nonproliferation initiatives, but instead aims to help experts and interested observers understand some of the underlying historical, political, and cultural bases on which national views in Europe on nuclear threats are founded. These papers help reveal a range of views on nuclear weapons and proliferation and shed light on some of the attitudes that underpin national policies on key issues.