When is war just? In the American tradition, the justice or injustice of war has turned primarily upon the circumstances immediately attending the initiation of force. The just war is the war waged in self defense or in collective defense against an armed attack. Conversely, the unjust war is the war initiated in circumstances other than those of self or collective defense against armed aggression. The American view of just war has thus been characterized by a singular preoccupation with the overt act of resorting to force. It has proceeded from the conviction that whatever a state's grievances, aggressive war is an unjust--and illegal--means for settling those grievances. This conviction was given full expression in the Gulf War.
The restriction of just war to the war of self or collective defense against armed aggression corresponds to the twentieth-century reconstruction of the Christian doctrine of bellum justum. In the classic version of the doctrine, the just war was a war of execution, an act of vindicative justice, taken to punish a state for a wrong done and unamended. But the rights in defense of which states might resort to war, in the absence of satisfactory alternative means of redress, were not restricted to that of self defense.
In the twentieth-century reconstruction, however, war is no longer a means generally permitted to states for the redress of rights that have been violated. Still less is war considered a legitimate means for changing the status quo. Armed force remains a means permitted to states only as a measure of defense against unjust attack. This restriction of just war rests in the main on the presumption--indeed, conviction--that war no longer serves as an apt and proportionate means for resolving international conflicts. International law has followed a similar course. The bellum legale, as the bellum justum, is now substantially limited to one of defense, individual or collective, against armed attack.