The foundations of the post-1945 international order, long anchored by U.S. leadership, are shifting. Amid intensifying geopolitical rivalry, democratic backsliding, and strategic fatigue in Washington, the question arises: what if the United States no longer plays its pivotal role in international security? From the escalating U.S.–China trade and tech war to growing security fragmentation in Europe and beyond, the international system is increasingly defined by competition, mistrust, and uncertainty. Simultaneously, the Global South is asserting new political and economic agency, complicating the old binaries of West vs. Rest. For Europe, this landscape is both a challenge and an inflection point. The continent faces renewed insecurity at its borders, questions about the future of NATO, and economic vulnerabilities tied to global supply chains. In response, the European Union has intensified its efforts at articulating an ambition for strategic sovereignty — in defense, technology, energy, and diplomacy. But can Europe move from aspiration to action if it must navigate this evolving world order without a reliable transatlantic partner?

This conference aims to explore the contours of a possible new world order where U.S. leadership is diminished, contested, or altogether absent. What would such a world look like? What role could — or should — European nations play in maintaining global stability, defending democratic values, and responding to crises in its neighborhood and beyond?