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Just war theory (jus ad bellum)

Page history last edited by John McMahon 4 years, 6 months ago

Just War Theory: Jus Ad Bellum




Justice is a human concept based on morality and fairness. When applying the theories of justice to human actions we derive a basic set of norms and behaviors that through the power allotted among states we, in turn, form a set of laws. These laws are intended to be comprehensive as a means of providing a state of order and peace. When those theories of justice are applied to international relations, we see a set of norms and behaviors that are formed around the act of going to war. This is the original basis of Just War Theory (JWT), and more specifically of Jus Ad Bellum, which translates literally to “right to war”. For instance, take the hypothetical example of a mugger unwarrantedly trying to take money from you. In this instance, we generally think you have the right to fight back against this threat to your property and life. War and violence are variations of conflict, a basic part of human experience. By limiting what is acceptable in war, we appeal to morality. 


Jus Ad Bellum is a conceptualization of when it is permitted to go to war, and what constitutes a justifiable reason for war. The limitations that are applied to war are also a way of mitigating the horror and destruction that surrounds war. It’s hard to think of when violence might be utilized to prevent further death and destruction, but interventionist wars, to prevent events like genocide, are another major component of Just War Theory, especially in the last half-century. When we think about war as right or just, we also have to consider how these set norms and behaviors vary between different governments, states, and societies as a whole. The differences between cultural groups provide one main arena for debate and discussion around Just War Theory. Intergovernmental organizations like the United Nations Security Council (UNSC) serve as the main functioning body when it comes to international conflict resolution. To avoid reducing what is seen as justice in war down to only a matter of perception, Just War Theory aims to provide a comprehensive set of norms and behaviors that we formulate to govern what happens within a state and among the international community. 


Major Debates and Questions:


The history of JWT, which dates back to the ancient world, is a synthesis of theological ideas, political philosophy, and international relations. Philosophers like Plato conceptualize early basics around the process of going to war and conduct in war. In the Republic, he asks “How must your soldiers behave towards each other and the enemies?” (Plato 1968, 468a) He concludes that enslaving your defeated enemies is an acceptable course of action because Greeks enslave other Greeks. While this page focuses on when it is just to go to war, you can also learn on this wiki about what is just during war in Just war theory (jus in bello) As just war theorists have developed the theory over time, contemporary views of individual justice have been added into their considerations. The abolishment of slavery as a normal practice in war shows that debates over social norms change the definition of various forms of justice. This is largely in part due to the amalgam of Christian morality and JWT.


Religion plays a key factor in defining societal norms and behaviors that are reflected in political policy. When Roman leaders wanted to declare war, they had to request permission from religious leaders. After a meeting with the religious leaders, diplomats would be sent to the other government with a list of demands and required reparations. If the demands were not met, the war would be legitimized, through legal institutions, as legally just (Lee 2012, 40). This is an early start to limiting military actions through a legal procedure. One of the most prominent Christian writers on JWT was St. Augustine of Hippo. His writings are one of the first to try and synthesize Christian morals and ethics with the immorality of war. Augustine’s idea in The City of God illuminates the relationship between morality and justice in war: “The use of force could be justified by explicitly connecting it to a moral cause, the pursuit of justice” (Goldstein 2008). He is the first to introduce the term “military necessity”: “Appealing to necessity allows states to claim that they are not responsible for the harm their wars do because they did not choose to fight, but are instead forced (by necessity) to fight.” (Lee 2012, 45) Regardless of the justness of the origins of a conflict, legal institutions, and due process, allow a state to show that declaring war was out of necessity. For Augustine, justifying war was for pious reasons. In what instances were devout followers of the “prince of peace” allowed to fight (Goldstein 2008)? That has evolved into the modern focus on holding the moral high ground. While part of JWT has changed throughout the years, there are still remnants of ancient political theory in modern conceptualizations. For example, the United States’ used military necessity as a justification frequently since the cold war era.


Since religion is a significant influence in social norms and behaviors, it is unsurprising there are alternate forms of the historically Christian JWT in the Islamic world. Considering we use the term “just war” as a common way to describe military actions in foreign policy, it's clear the West values the distinction that their actions are somehow connected to justice. Jihad is used similarly in the Islamic world, striving to connect to the morality of the teachings of Muhammed with justice around war: “There is significant overlap between the Islamic and Western just-war traditions on the matter of applying moral constraints to military conduct, including the consideration of noncombatant immunity, just cause, and restricting the authority of those who have the right to call for the use of force. ‘You shall not kill -- for that is forbidden -- except for a just cause,’ reads one often-cited verse from the Koran.” (Goldstein 2008) The use of the phrase “just cause” in a Koran is also a direct quote from one of the criteria in evaluating if a war is just in the Jus ad Bellum test. Even though Western JWT and the Islamic world are from different theological origins, they have similarities in the role religious morality plays in defining what is just. 


Most modern issues and debates on Just War Theory are over state sovereignty, morality, and human rights. The five main criteria often used to define if a war is “just” in accordance with Jus ad Bellum test:

  1. Presence of just cause

  2. Presence of competent authority to act [Legitimacy]

  3. Right Intention in Action

  4. Reasonable hope of success

  5. Overall proportionality of good (in ends desired) (Butler 2003, 232)


The United States as the strongest military force in the world has a tumultuous relationship with Jus ad Bellum. Its notorious reputation of interfering within other countries’ borders is a violation of JWT. The justification is that intervention is for the greater good of the people in that state. However, these actions rarely qualify as “just” in JWT. In fact, “just cause” is defined as a “wrong” done to a state. (Lee 2012, 77) So what gives the United States the legitimate authority to qualify what’s best for the citizens of another sovereign state? International Humanitarian Law (IHL) has made this question harder to answer. IHL makes the global community responsible for protecting universal human rights of non-combatants regardless of what state they are residing in. This applies even when a state enters into a war for unjust reasons. IHL is predominantly centered in Jus in Bello (conduct in war), but a violation of IHL acts as a just cause for intervention. “In theoretical terms, the bias against or (virtual) ban on intervention was often defended on grounds of the importance of the integrity of nation-states within the world order.” (Coady 2005, 1) The issue over legitimate authority dealing with injustice in sovereign states would not fit into JWT. To address this, a new cosmopolitan approach alleges that two moral amendments to reframe JWT: “(A) individuals are the fundamental units of moral concern and ought to be regarded as one another’s moral equals; (B) whatever rights and privileges states have, they have them only in so far as they thereby serve individuals’ fundamental interests...” (Fabre 2008, 964) In other words, if a state fails to fulfill its duties to its citizens, the global community has legitimate authority to protect them. Trying to protect the rights of the global community, has given rise to the necessity of international institutions such as the United Nations in rectifying injustice in sovereign states. 


International Institution:


The United Nations (UN), formed after World War II, is arguably the most effective international organization in facilitating global conflict resolution before resorting to war. Their efforts have been successful since there have been significantly less global conflicts since the 1950s and most wars have been internal conflicts. It is the closest the world has come to Kant’s idea of the “Federation of Peoples” in his text on Perpetual Peace: “Each nation, for the sake of its own security, can and ought to demand of the others that they should enter along with it into a constitution, similar to a civil one, within which the right’s of each could be secured” (Kant 1795, 102). The UN is involved in more than peace and security efforts, including managing humanitarian efforts to help those affected by military conflicts around the globe. By working to prevent wars of aggression, this organization helps to provide a level of justice to international relations. In the event of any transgression against one of its member states, the UN can respond through means such as arbitration, sanctions, or the use of peacekeepers. The cooperation of most of the world’s countries through the UN seeks to legitimize the justness of their actions. This preventative power through the cooperation of 192 member states is coordinated by the UN Security Council. The Council is made up of fifteen members, five of them permanent: United States, China, Russia, the United Kingdom, and France. The other ten members change every two years based on elections from the General Assembly. This attempts to ensure that even the smallest countries have a voice on issues of global peace and security. The Security Council also works with the General Assembly to elect judges to the International Court of Justice, which provides an additional, separate level of accountability. In its Charter, there are three major procedures that show the UN’s commitment to ensuring justice when it comes to warfare:

  • Article 33: The parties to any dispute, the continuance of which is likely to endanger the maintenance of international peace and security, shall, first of all, seek a solution by negotiation, enquiry, mediation, conciliation, arbitration, judicial settlement, resort to regional agencies or arrangements, or other peaceful means of their own choice.

  • Article 34: The Security Council may investigate any dispute, or any situation which might lead to international friction or give rise to a dispute, in order to determine whether the continuance of the dispute or situation is likely to endanger the maintenance of international peace and security.

  • Article 41 and 42: The Security Council may decide what measures not involving the use of armed force are to be employed to give effect to its decisions, and it may call upon the Members of the United Nations to apply such measures. These may include complete or partial interruption of economic relations and of rail, sea, air, postal, telegraphic, radio, and other means of communication, and the severance of diplomatic relations; Should the Security Council consider that measures provided for in Article 41 would be inadequate or have proved to be inadequate, it may take such action by air, sea, or land forces as may be necessary to maintain or restore international peace and security. Such action may include demonstrations, blockade, and other operations by air, sea, or land forces of Members of the United Nations. (Chapter VII 2015)


We can see from the UN Charter that the UN version of Just War would ultimately be no war at all. However, interventionist strategies are acceptable under the principles such as the responsibility to protect. This goes back to the cosmopolitan application to JWT and expands this theory to incorporate morality and other theories of justice.


Connection to broader theories of justice:


Economic sanctions as a non-violent form of diplomatic pressure might seem like a better alternative than a declaration of war. However, through sanctions, there are far greater implications on economic justice for the citizens of that affected state. Immediately following the Persian Gulf War, Iraq had sanctions levied against it for its unjust invasion of Kuwait. After 4 months, Iraq did not capitulate to the UN’s demands. Military action was believed to be required to liberate the sovereign state of Kuwait. Iraq was under the despotic leadership of Saddam Hussain. The economic sanctions didn’t affect the political elite as much as it hurt the Iraqi population. It’s estimated that the total number of Iraqi civilian deaths, (combat included, though most are non-combat) exceeds 150,000. (Jones 1998, 8) The high number of civilians killed could be viewed as a violation of the proportionality criteria in JWT. When the international community condemns individuals of a state to suffer for the decisions of the elite, we violate economic justice. Especially when their freedom of movement is limited. If we want to act to rectify injustice it has to be done in a way that doesn’t perpetuate further injustice. This is a difficult task, but the utilization of soft power in international relations is key to maintaining the moral high ground. Countries of Western liberal democracies have a privilege which makes restricting access to necessary resources in another country, while limiting the individual's ability to migrate, unjust. (Carens 1987, 2) Considering this, if the West wanted to remain just while addressing Iraq’s violation of JWT (the invasion of Kuwait), the West would have considered the consequences of the military intervention and economic sanctions on the Iraqi citizens.


The goal of Kant’s Perpetual Peace is to argue that we can strive for a world where JWT theory is no longer needed. He advocates for a cosmopolitan approach to universal morality and hospitality. This can only be achieved if the power of the state is intertwined within a sovereign country’s people, as they will fear the consequences to their power. For Kant, Governments around the world would have to base their constitution around republican values” (Kant 1795, 10). When we consider the criteria of Legitimate Authority in Jus ad Bellum, Kant’s idea of a world dominated by republican governments would give authority to the individual’s who reside in the state. This would address a serious point of contention in JWT and provide individual justice to the member’s of these republican states. 



Just War Theory dominated International Relations since WWII and the rise of the globalized world. JWT emphasizes the role of morality in choosing to go to war. As conventional war is in decline, so is the legitimacy of traditional JWT. There is a priority of human rights over state sovereignty. The rise of cosmopolitan theories of justice being applied to JWT has placed an increased importance on global institutions committed to preserving justice in war like the UN. The future of JWT is to improve our understanding of the necessity of a comprehensive plan of action for dealing with non-state actors and human rights violations not considered in the original theory. The synthesis of other forms of justice into dealing with war is critical in achieving true justice around war.



  • Butler, Michael J. 2003. “U.S. Military Intervention in Crisis, 1945-1994: An Empirical Inquiry Of Just War Theory.” Journal of Conflict Resolution 47(2): 226–48.

  • Carens, Joseph H. 1987. "Aliens And Citizens: The Case For Open Borders." The Review of Politics 49(2): 251-273.

  • Coady, T., 2005, “Intervention and the Dangers of Moralism” Global Dialogue 7, no. 1/2 (January 1, 2005): 68–75.

  • Fabre, Cécile, 2008, “Cosmopolitanism, Just War Theory and Legitimate Authority”, International Affairs, 84(5): 963–76.

  • Goldstein, Evan R. 2019, "How Just Is Islam's Just-War Tradition?" The Chronicle of Higher Education (Apr. 2008) Business Insights: Essentials

  • Jones, Lawrence W. 1998. “The Persian Gulf War: A Case Study in Just War Theory” Defense Technical Information Center

  • Kant, Immanuel. 1903. Perpetual peace; a philosophical essay, 1795. London: S. Sonnenschein.

  • Lee, S., 2012, Ethics and War: An Introduction, New York: Cambridge University Press.

  • Plato, and Allan Bloom. 1968. The Republic. New York: Basic Books.

  • U.N. Charter art. VII


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