Europe’s security is heavily dependent on the United States. Even beyond NATO, the United States is a key player in European security through its bilateral engagement with numerous European states. Against that backdrop, a changing transatlantic relationship has considerable implications for European security. This is the context in which European defense cooperation will need to find answers to an ever more challenging security environment. Yet there is no single “European” reading of the situation. Instead, Europeans are stuck in debates with various capitals talking past each other, rather than addressing the Grand Strategy issues at hand. This chapter intends to provide an overview of these implications and debates and seeks to identify the issues that ought to be on Europe’s (future) agenda.