Why has interstate war declined and why do states refrain from territorial conquests in the post-Second World War order? The 1928 Peace Pact cannot account for these remarkable developments. This article argues that outlawing war is not enough to promote international peace. International Relations debates on the influence of weapons of mass destruction, democratic regime types and political cultures on interstate behaviour provide further important insights into the delegitimation of certain types of war. Since the 1990s, a changing character of war and warfare has emerged that is especially promoted by democratic states. How democratic states have justified their military use of force and how they have conducted their military interventions has a strong and ambivalent impact on the liberal world order.
