Just War Doctrine — Criteria
The doctrine of justifiable war assumes a presumption against war — war should not be launched unless all the criteria are met (jus ad bellum), the war will be fought in a moral way (jus in bello), and it will be ended in a moral way (jus post bellum). There is no “official” set of criteria, but the following criteria are the main ones typically suggested.
Jus ad bellum (what justifies going to war)
Just Cause — Force may be used only to correct a grave, public harm, such as defending against unjust aggression or intervening to stop massive violation of basic human rights of whole populations (such as genocide).
Legitimate Authority — War must serve public and not merely private purposes. So only duly constituted authorities at the highest levels of a legitimate government — those who bear the responsibility to decide matters that are for the good of the people — can make the decision and they must do so publicly. Private armies cannot conduct their own wars.
Formal Declaration — Before using force, a country/entity must make a formal declaration of war and delineate its aims.
Right Intention — War must be waged for the sake of a just cause, not out of ethnic hatred, for revenge, for wanton killing and destruction, for material gain, nor to grab power. War‘s ultimate goal must be reconciliation and the restoration of justice. In addition, those who undertake war, even for a justifiable cause, should act not with arrogance or self-righteousness, but with humility, regret, and full recognition of the humanity of their adversaries.
Probability of Success — Arms may not be used in a futile cause or in a case where disproportionate measures are required to achieve success. It is not right to wreak widespread havoc for a lost cause, even if the war is defensive.
Proportionality — The good a war will accomplish — or the evil it will prevent — in total must outweigh the totality of suffering it will inevitably cause to all parties. It is morally wrong to make matters worse.
Last Resort — Force may be used only after all peaceful and viable alternatives have been seriously tried and exhausted, especially good-faith diplomatic negotiations.
Jus in bello (how combatants must act)
Discrimination and Non-Combatant Immunity — War must only be directed towards those engaged in harm — enemy combatants — and not towards civilians caught in circumstances they did not create. Only attacks on legitimate military, political, and industrial targets involved in rights-violating harm are permitted. Attacks on civilian factories supporting the war effort are questionable. While some collateral civilian casualties are excusable, intentional attacks upon non-combatants or prisoners are clearly forbidden. Weapons of mass destruction, because they kill and maim so many civilians, cannot be used.
No Atrocious Weapons — No horrendous weapons (like chemical and biological weapons) or tactics (like mass rape or genocide) can be used. Treachery, like disguising soldiers to look like civilians, cannot be used.
Proportionality — No more force can be used than is required to succeed — wanton killing and destruction are not allowed and collateral civilian deaths must be minimal.
Prisoners of War (POWs) Treated Humanely — Enemy soldiers who surrender are no longer causing harm and so must be treated well.
No Reprisals — Banned weapons and tactics cannot be used in retaliation for the other side using them.
No Repression of One‘s Own Civilians — The human rights of one‘s own population must be respected (and not thrown out in the name of national security).
Jus post bellum (how war must be terminated)
Just Cause for Termination — A state must terminate a war if there has been a reasonable vindication of the rights that were violated in the first place, and if the aggressor is willing to negotiate the terms of surrender (including a formal apology, compensations, war crimes trials, and perhaps rehabilitation).
Public Declaration and Authority — The terms of peace must be made publicly by a legitimate authority, and a legitimate authority must accept the terms.
Right Intention — Revenge against the loser is not permitted.
Discrimination — The victor state is to differentiate between political and military leaders, and combatants and civilians. Punitive measures are to be limited to those directly responsible for the conflict. The victor state must be willing to apply the same level of objectivity and investigation into any war crimes its own armed forces may have committed.
Proportionality — Any terms of surrender must be proportional to the rights that were initially violated. Draconian measures, absolutionist crusades and any attempt at denying the surrendered country the right to participate in the world community are not permitted.
Rehabilitation — The victor state may require changes in the aggressor state‘s institutions (demilitarization, police and judicial retraining, human rights education, etc.), but these reforms must be carried out with the goal of establishing a vibrant civil society that will protect human rights (not a client state subservient to the victor).
Orend, Brian, “War,” The Stanford Encyclopedia of Philosophy (Winter 2005 Edition), Edward N. Zalta (ed.), http://plato.stanford.edu/archives/win2005/entries/war/.
Wikipedia contributors, “Just War,” Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Just_War&oldid=195729287 (accessed March 7, 2008).
Rasor, Paul, “Prophetic Nonviolence: Toward a Unitarian Universalist theology of war and peace,” UU World, Spring 2008. http://www.uuworld.org/ideas/articles/68490.shtml