War is a necessary element in international affairs when there is no scope for diplomacy and conditions dictate that force is necessary to prevent or stop suffering. Few would argue that the United States was acting unjustly in entering the 2nd World War, or that more generally the defeat of the Nazis was an unjust act on the behalf of the Allies.  Furthermore, just war theory has little to say on the overall existence of war, but merely seeks to regulate war as a permanent feature of international society. War, as an institution and a human activity, has existed for as long as there have been political communities. The resort to force is therefore not one made due merely to a belief in its legitimacy but a belief in its utility. Just war theory acts therefore as a series of moral criteria to regulate the resort to warfare in order to prevent, rather than exacerbate, war for war’s sake. It recognizes the ‘war is hell’ mentality and is, if anything, born from it, encouraging a resort to force only in cases where diplomacy is unable to function and war is strictly necessary. Even then, jus in bello principles apply to regulate the conflict itself, ensuring that a just war does not descend into the use of illegitimate means and methods of warfare. It does not purport to comment on the matter of the existence of warfare, merely recognises its occurrence and seeks to regulate both its regularity and bloodshed.