How does peace between states become an established social fact or part of the unquestioned order of things? This question drives Vincent Pouliot’s International Security in Practice, an innovative and provocative contribution to the theoretical literature on international security, with an empirical focus on post-Cold War Russian-Atlantic security relations. While the challenge of theorizing the causes and conditions of war and peace between states is ‘ancient’ in the discipline of International Relations (IR), the challenge of enacting transatlantic peace became a novel and urgent practical concern in world politics following the collapse of the Soviet Union and the end of the U.S.-USSR superpower rivalry, a set of events which opened up a rare opportunity for the pacification of relations between former enemies. Although there were initial promising signs in the early 1990s of great transformations in security relations between Russia and the West, transatlantic peace has materialized only as a fragile and somewhat fleeting achievement. Why was the hope of a robust and enduring post-Cold War transatlantic peace stillborn (p. 191)?