This book analyses and compares instances of the diffusion of political norms and ideas in the history of Franco-German relations. While this relationship is often described as a history evolving from enmity over reconciliation to friendship, the book uses the concept of diffusion as a complementary analytical perspective to emphasize how political norms and ideas originating in one society have influenced the other, especially in periods of intergovernmental conflict. Established in International Relations to explain transnational normative change in contemporary contexts, the framework of diffusion is heuristically useful to explore how various types of actors have contributed, using analytically different mechanisms, to normative change across the