The just war theory () is a doctrine, also referred to as a tradition, of military ethics that aims to ensure that a war is morally justifiable through a series of criteria, all of which must be met for a war to be considered just. It has been studied by military leaders, theologians, ethicists and policymakers. The criteria are split into two groups: ("right to go to war") and ("right conduct in war"). There have been calls for the inclusion of a third category of just war theory (jus post bellum) dealing with the morality of post-war settlement and reconstruction. The just war theory postulates that war, while it is terrible but less so with the right conduct, is not always the worst option, but justifiable when justice is an objective of armed conflict. Important responsibilities, undesirable outcomes, or preventable atrocities may justify war.
Opponents of the just war theory may either be inclined to a stricter pacifist standard (proposing that there has never been nor can there ever be a justifiable basis for war) or they may be inclined toward a more permissive nationalist standard (proposing that a war need only to serve a nation's interests to be justifiable). In many cases, philosophers state that individuals do not need to be plagued by a guilty conscience if they are required to fight. A few philosophers ennoble the virtues of the soldier while they also declare their apprehensions for war itself. A few, such as Rousseau, argue for insurrection against oppressive rule.
The historical aspect, or the "just war tradition", deals with the historical body of rules or agreements that have applied in various wars across the ages. The just war tradition also considers the writings of various philosophers and lawyers through history, and examines both their philosophical visions of war's ethical limits and whether their thoughts have contributed to the body of conventions that have evolved to guide war and warfare.
In the twenty-first century there has been significant debate between traditional just war theorists, who largely support the existing law of war and develop arguments to support it, and revisionists who reject many traditional assumptions, although not necessarily advocating a change in the law.
Origins Ancient Egypt A 2017 study found that the just war tradition can be traced as far back as to Ancient Egypt. Egyptian ethics of war usually centered on three main ideas, these including the cosmological role of Egypt, the pharaoh as a divine office and executor of the will of the gods, and the superiority of the Egyptian state and population over all other states and people. Egyptian political theology held that the pharaoh had the exclusive legitimacy in justly initiating a war, usually claimed to carry out the will of the gods. Senusret I, in the Twelfth Dynasty, claimed, "I was nursed to be a conqueror...his [Atum's] son and his protector, he gave me to conquer what he conquered." Later pharaohs also considered their sonship of the god Amun-Re as granting them absolute ability to declare war on the deity's behalf. Pharaohs often visited temples prior to initiating campaigns, where the pharaoh was believed to receive their commands of war from the deities. For example, Kamose claimed that "I went north because I was strong (enough) to attack the Asiatics through the command of Amon, the just of counsels." A stele erected by Thutmose III at the Temple of Amun at Karnak "provides an unequivocal statement of the pharaoh's divine mandate to wage war on his enemies." As the period of the New Kingdom progressed and Egypt heightened its territorial ambition, so did the invocation of just war aid the justification of these efforts. The universal principle of Maat, signifying order and justice, was central to the Egyptian notion of just war and its ability to guarantee Egypt virtually no limits on what it could take, do, or use to guarantee the ambitions of the state.
India The Indian Hindu epic, the Mahabharata, offers the first written discussions of a "just war" (dharma-yuddha or "righteous war"). In it, one of five ruling brothers (Pandavas) asks if the suffering caused by war can ever be justified. A long discussion then ensues between the siblings, establishing criteria like proportionality (chariots cannot attack cavalry, only other chariots; no attacking people in distress), just means (no poisoned or barbed arrows), just cause (no attacking out of rage), and fair treatment of captives and the wounded.
In Sikhism, the term dharamyudh describes a war that is fought for just, righteous or religious reasons, especially in defence of one's own beliefs. Though some core tenets in the Sikh religion are understood to emphasise peace and nonviolence, especially before the 1606 execution of Guru Arjan by Mughal Emperor Jahangir, military force may be justified if all peaceful means to settle a conflict have been exhausted, thus resulting in a dharamyudh.
East Asian Chinese philosophy produced a massive body of work on warfare, much of it during the Zhou dynasty, especially the Warring States era. War was justified only as a last resort and only by the rightful sovereign; however, questioning the decision of the emperor concerning the necessity of a military action was not permissible. The success of a military campaign was sufficient proof that the campaign had been righteous.
Japan did not develop its own doctrine of just war but between the 5th and the 7th centuries drew heavily from Chinese philosophy, and especially Confucian views. As part of the Japanese campaign to take the northeastern island Honshu, Japanese military action was portrayed as an effort to "pacify" the Emishi people, who were likened to "bandits" and "wild-hearted wolf cubs" and accused of invading Japan's frontier lands.
Ancient Greece and Rome The notion of just war in Europe originates and is developed first in ancient Greece and then in the Roman Empire.Gregory Raymond, The Greco-Roman Roots of the Western Just War Tradition, Routledge 2010.Rory Cox, "The Ethics of War up to Thomas Aquinas" in (eds. Lazar & Frowe) The Oxford Handbook of Ethics of War, Oxford 2018.Cian O'Driscoll, "Rewriting the Just War Tradition: Just War in Classical Greek Political Thought and Practice," International Studies Quarterly (2015).
It was Aristotle who first introduced the concept and terminology to the Hellenic world that called war a last resort requiring conduct that would allow the restoration of peace. Aristotle argues that the cultivation of a military is necessary and good for the purpose of self-defense, not for conquering: "The proper object of practising military training is not in order that men may enslave those who do not deserve slavery, but in order that first they may themselves avoid becoming enslaved to others" (Politics, Book 7).
Stoic philosopher Panaetius considered war inhuman, but contemplated just war when it was impossible to bring peace and justice by peaceful means. Just war could be waged solely for retribution or defense, in both cases having to be declared officially. He also established the importance of treating the defeated in a civilized way, especially those who surrendered, even after a prolonged conflict.
In ancient Rome, a "just cause" for war might include the necessity of repelling an invasion, or retaliation for pillaging or a breach of treaty.Livy 9.1.10; Cicero, Divinatio in Caecilium 63; De provinciis consularibus 4; Ad Atticum VII 14, 3; IX 19, 1; Pro rege Deiotauro 13; De officiis I 36; Philippicae XI 37; XIII 35; De re publica II 31; III 35; Isidore of Seville, Origines XVIII 1, 2; Modestinus, Libro I regolarum = Digesta I 3, 40; E. Badian, Roman Imperialism in the Late Republic (Ithaca 1968, 2nd ed.), p. 11. War was always potentially nefas ("wrong, forbidden"), and risked religious pollution and divine disfavor.William Warde Fowler, The Roman Festivals of the Period of the Republic (London 1925), pp. 33ff.; M. Kaser, Das altroemische Ius (Goettingen 1949), pp. 22ff; P. Catalano, Linee del sistema sovrannazionale romano (Torino 1965), pp. 14ff.; W. V. Harris, War and imperialism in Republican Rome, 327-70 B.C. (Oxford 1979), pp. 161 ff. A "just war" (bellum iustum) thus required a ritualized declaration by the fetial priests.Livy 1.32; 31.8.3; 36.3.9 More broadly, conventions of war and treaty-making were part of the ius gentium, the "law of nations", the customary moral obligations regarded as innate and universal to human beings.Cicero, De officiis 3.17.69; Marcia L. Colish, The Stoic Tradition from Antiquity to the Early Middle Ages (Brill, 1980), p. 150.
Christian views Christian Just War thinking is often thought to begin with Saint Ambrose, Bishop of Milan, before being developed further by his contemporary Saint Augustine of Hippo.Delahunty, Robert J. “The Returning Warrior and the Limits of Just War Theory.” Rutgers Journal of Law & Religion 15 (2013):p.249 The Just War theory, with some amendments, is still used by Christians today as a guide to whether or not a war can be justified, and how it should be fought. Christians may argue "Sometimes war may be necessary and right, even though it may not be good." In the case of a country that has been invaded by an occupying force, for example, war may be the only way to restore justice.
Saint Ambrose Influenced by Roman law, and Cicero in particular, Ambrose believed that war was legitimate only for defensive purposes or the punishment of serious wrongdoing, and rulers were obliged to respect treaties, avoid exploiting enemies and treat the defeated with mercy.Delahunty, Robert J. “The Returning Warrior and the Limits of Just War Theory.” Rutgers Journal of Law & Religion 15 (2013): pp. 249-250. Ambrose also seems to have regarded military force as permissible against heretics, or in support of Christian orthodoxy.Ibid. Nevertheless, he strictly prohibited the Church from direct involvement in violence, insisting that clergy must not take up arms themselves. Similarly, warfare had to be undertaken only to fulfill divine law, not for personal motives, and any war driven by emotional excess, vindictiveness or other disordered intentions fell outside the moral limits he envisioned.
Saint Augustine Saint Augustine held that Christians should not resort immediately to violence, but that God has given the sword to governments for a good reason (based upon Romans 13:4). In Contra Faustum Manichaeum book 22 sections 69–76, the main source for his just war ideas, Augustine argues that Christians, as part of a government, need not be ashamed of protecting peace and punishing wickedness when they are obliged to do so. Augustine regarded intention as the main determinant of whether a war was just or sinful: "What is here required is not a bodily action, but an inward disposition. The sacred seat of virtue is the heart."
Nonetheless, Augustine asserted that peaceful inaction in the face of a grave wrong that could be rectified only by violence would be a sin. Defense of oneself or the innocent could therefore be a necessity, especially when authorized by a legitimate state authority:They who have waged war in obedience to the divine command, or in conformity with His laws, have represented in their persons the public justice or the wisdom of government, and in this capacity have put to death wicked men; such persons have by no means violated the commandment, "Thou shalt not kill."
But, say they, the wise man will wage Just Wars. As if he would not all the rather lament the necessity of just wars, if he remembers that he is a man; for if they were not just he would not wage them, and would therefore be delivered from all wars.
No war is undertaken by a good state except on behalf of good faith or for safety.City of God, 22.6, quoted in The text seems from a missing fragment of Cicero's dialog On the Republic, by the Laelius character.