Our article focuses on the likely impact of France's return to NATO's integrated military command on the future of the European security and defense policy (ESDP). First, we describe the triangular relationship between France's defense, NATO and European defense policies that dominated the era of the Gaullist-Mitterrandist consensus (1958-95) and its gradual erosion under Jacques Chirac's tenure (1995-2007). Second, we explain the context in which President Sarkozy made the decision in 2007 to rejoin the Allied military command. Relying on interviews with French foreign and defense policy-makers, we address the extent to which ESDP considerations really played a role. Finally, we develop four scenarios for the future of European defense: (1) ESDP gets a new lease of life; (2) France becomes a normal player in a NATO-dominated Europe; (3) NATO and ESDP work out of a division of labor; and (4) France becomes the Trojan horse of European cooperation inside NATO. To develop each scenario, we rely on rationalist and constructivist mechanisms drawn from International Relations theory.