Chapter 21 offers a new, Atlantic interpretation of the peace of Versailles and the reconfigured international order that emerged in 1919. In contrast to previous assessments, especially the long dominant view that the settlement represented the best possible outcome, it argues that what the “peacemakers” managed to negotiate could only lay a frail groundwork for lasting peace and a sustainable world order of democratic states. It emphasises that the peace architecture of 1919 remained truncated in crucial respects – particularly because it neither integrated the Weimar Republic nor provided effective mechanisms to come to terms with the German question, the dramatic consequences of the Great War and the broader structural and systemic challenges of the “long” 20th century. It illuminates that this was especially due to the fact that the overburdened key decision-makers of Paris confronted one novel, overriding challenge they could only meet in a very limited manner: to forge sustainable transatlantic compromises that reconciled very disparate aims and conceptions – and to create a robust, integrative and thus also more legitimate transatlantic superstructure of security and stabilisation. Finally, it highlights that the learning processes the war had engendered did not reach far enough to permit more far-reaching advances.