Just War Theory: It’s Hard to Fight if the Fight’s Not Fair


Imagine that your sibling steals your sweatshirt. It was wrong of them to take, and the only way to right that wrong is to take it back. So you sneak into their room and grab your hoodie. While you're looking for it, you uncover their candy stash. You decide to pocket a piece of candy in retaliation. Now you've got your hoodie back and a sweet treat, and your sibling will hopefully learn not to steal your stuff. Was this a fair way to end the conflict? 


Just War Theory is a fancy way to ask questions about how and why people fight wars. Throughout history, people have competed for resources. Principles of honor and warfare were present in ancient Egyptian and Greek civilizations. Catholic theologians in the middle ages like St. Augustine and St. Thomas Aquinas developed the modern written theory of just war. These philosophers wanted to reconcile the belief that taking a life was wrong with a state's duty to defend its people and the necessity of violence in some circumstances. 

Just War Theory

Just War Theory provides a framework for states in conflict. It stresses that every effort to prevent wars must be made. According to Just War Theory, violence is only permissible when it is a lesser evil than the alternatives. For a battle to be considered morally permissible, it must be ethical before, during, and after the conflict. Respectively, the Latin jus ad bellum, jus in bellum, and jus post bellum describes these parts.

Qualifications of Justice: Before, During, and After War

Jus ad bellum describes justice before a war. To enter war, states must have a reasonable chance of success, attempt all other options of negotiation, and have the intention to right a wrong, not gain materials. War should be proportional to its harms. If nation Y invades and acquires land from nation X, nation X has a just cause to take the area back. However, nation X should only aim to restore its lost property, not take additional land from nation Y, nor punish them further with trade embargoes or nuclear warfare. War must also be declared by the right authority. The political power of a sovereign state, rather than just any individual or group, is the only proper party that can make that decision. According to Just War Theory, the reason for war should be to protect innocent life from danger. For example, if genocide is occurring in a country, war is justified as it aids the victims. In essence, the cause of war must be in self-defense or other’s defense to be ethical. 

Jus in bellum, or justice during war, describes the actions a country can fairly take in battle. For example, civilians, injured soldiers, captives, or people who surrendered should not be attacked. Harming the civilian population, such as through the destruction of land or natural resources common in combat, should attempt to be moderate and only for military necessity. Weapons and other methods of warfare that cause mass destruction are prohibited. Nations must treat war prisoners fairly and abstain from torture. 

Jus post bellum, or justice after a conflict, is vital for proper restorations. Similar to starting the war with just cause, there must be an ethical reason for ending the war. Did the countries affected apologize, surrender, negotiate terms, and promise not to seek revenge?  In essence, the terms of surrender should be proportional to the wrongs done. The declaration of peace should be made and accepted by proper authorities. Often, war has torn nations apart, and repairs need to be made. Peace treaties, environmental remediations, war crime trials, or reparations may be necessary for justice. Military and political leaders bear a greater burden of repairing damage than the combatants and civilians. 

Ethical Frameworks 

There is the question of whether morality has a place in such an immoral act as war. Pacifists believe that all war is immoral and should not occur under any circumstances. Other schools of thought that have influenced the discussion of morality’s place in war include consequentialism, which is concerned only with the outcomes of actions, and intrinsicism, which considers acts as inherently good or bad, regardless of the outcome. For example, an ethical war for consequentialists uses the minimum amount of time and money to encourage a clean fight with no need for revenge. Intrinsicists consider actions themselves in war to be good or evil, such as protection for doctors or a ban on nuclear weapons. Ethics can become challenging to discern, such as when military targets hide in civilian centers. While the intention may be only to kill the military leader, the foreseeable result of innocent lives lost is not accidental. 

Within Just War Theory, there are influences of both models. Because there is no strict ethical framework, the theory itself is applied broadly. Moral situations are not black and white. With such broad rules for justification, a war can both fit the criteria and violate it based on individual interpretations. 

Why Care?

Just War Theory reminds us of our humanness. In war, enemies of different religions, races, or languages tend to dehumanize one another.  When they are all seen as people, all sharing a moral code, wars may generate less harm. 

No government can send people to die without reason, and Just War Theory examines if there are any good reasons for war. Just War Theory points to fighting as something we can only be motivated to do to protect each other, not for resources, the ruling government, or power.

Think Further

  1. Think about a past war or conflict, and apply Just War Theory. Was the war just? What before, during, or after the conflict would have made it moreso?
  2. Are there cases where jus ad/in/post bellum should not be considered, or where a war was just even if a violation in Just War Theory occurred? Which category is most important? Why? 
  3. When you think about violence, are you a consequentialist (concerned with the outcomes), intrinsicist (concerned with the good or bad in actions), or pacifist (believing all war is immoral)? What school of thought do you tend to agree with, and why? 


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Learn More

  1. Moseley, Alexander. “Just War Theory.” Internet Encyclopedia of Philosophy, IPE, www.iep.utm.edu/justwar/.
  2. Lango, John W. “Just War Theory.” The Ethics of Armed Conflict: A Cosmopolitan Just War Theory, 2014, pp. 18–47.
  3. The Ethics Centre 19 JUL 2016. “Just War Theory.” THE ETHICS CENTRE, 16 Nov. 2018, ethics.org.au/ethics-explainer-just-war/.