States rarely declare war. For many international law scholars, just war theorists, and moral philosophers, the declaration of war is a moribund tradition that serves no important purpose. When declarations of war are defended, the argument is situated in the war powers debate about executive authority. In contrast, I argue that declaring war – making conditional and reasoned moral demands – continues to be an important requirement for just wars. States should declare war because states should make explicit (formal) moral demands before fighting. Declaring war is procedurally important because it ensures that a state makes a formal moral case, showing respect to innocent third parties whose interests are affected and providing targets the right to confront their accusers and hear evidence. While not a panacea, requiring declarations is a significant improvement on the ad hoc politics of wartime justification that plagues wars such as Iraq. Further, declarations, as ultimatums, are the only reasonable interpretation of the ‘last resort’ requirement in just war theory. A final section extends the argument to contemporary wars against non-state actors, showing that a politics of recognition underlying declarations of war may prove especially fruitful today.
