ABSTRACT
This chapter explains the origins of the characterization of preventive war as aggression and the process through which the legitimate self-defence interpretation emerged, and explores how the conceptual shift has fundamentally altered the domestic political setting for considering preventive war as an option to deal with future power shifts. Rival claims about the legitimacy of preventive war are closely tied to a century-long debate over the conditions that justify the use of military force. World War I, and the horrible toll it exacted in blood, economic ruin and political upheaval, was a profound external shock to beliefs about war so blithely accepted for generations. The passage of time alone helps explain why the ‘preventive war is aggression’ interpretation was weakening by the early 1990s. The most common argument marshalled to justify preventive war was a normative claim that America could consider it a legitimate act of self-defence against an enemy dedicated to America’s destruction.
