Just-war theory focuses on two issues: the justice of the decision to wage war and the justice of war conduct. About the war decision, just-war theorists require that decision makers have legal authority to wage war, that the cause to wage war be just, and that participants have a right intention. Just cause requires not only that the war be just in the sense of aiming to rectify a wrong, but also that the cause be proportionate to the death and destruction likely to result from the war. Just cause also requires that all reasonable means to avoid war have been exhausted, and that there be a reasonable hope of success. Since World War I, just-war theorists have allowed only national or collective self-defense as just cause for war.

For the criteria of war conduct, just-war theorists invoke two principles. The first is one of discrimination...