France and the United Kingdom have signed a series of agreements that will deepen bilateral defense cooperation across nuclear policy, industrial development and support for Ukraine, reflecting growing European momentum to accelerate strategic autonomy and positioning London and Paris as central actors in shaping the Continent's future security architecture. However, entrenched European divisions and material constraints will hinder progress toward a fully integrated European nuclear posture. French President Emmanuel Macron and U.K. Prime Minister Keir Starmer announced on July 10 a series of deals expanding bilateral strategic cooperation on nuclear deterrence, defense industry ties and support for Ukraine. As part of the defense package, France and the United Kingdom formalized plans to coordinate their nuclear arsenals in response to extreme security threats in Europe and update the 2010 Lancaster House treaties to include operational force integration in new domains such as space and cyber. The two leaders also confirmed additional...