The argument of this paper is that the Atlantic order is in the midst of a fundamental transition. The transatlantic discord that has emerged since the late 1990s marks a historical breakpoint; foundational principles of the Atlantic security order that emerged after World War II have been compromised. Mutual trust has eroded, institutionalized cooperation can no longer be taken for granted, and a shared Western identity has attenuated. To be sure, the Atlantic democracies continue to constitute a unique political grouping. But as scholars and policy makers alike struggle to diagnose the troubles that have befallen the Atlantic community and to prescribe mechanisms for redressing the discord, they would be wise to recognize the scope of change that has been taking place in the Atlantic order.