Beyond Trending: What is just war?

Just war theory

Just war theory is an ethical framework that concerns itself with why and how wars are fought. The theory is traced to medieval Christian just war tradition, where St. Augustine and Thomas Aquinas made significant contributions to its development. While Augustine’s comments offer a biblical rationale for war, Aquinas delineates the general principles of the just war theory. 

Aquinas engages with the question of not only the justification of war but also with the conduct during the war. These two questions constitute the two key components of the theory, referred to by their Latin names:

 Jus ad bellum – Outlining the justifications for entering a war.

Jus in bello – Governing the conduct during warfare. 

The theory evolved over the years to incorporate both theological and secular perspectives on warfare, but the framework suggested by Aquinas continues to define it. It largely revolves around key principles of jus ad bellum and Jus in bello that distinguish just wars from unjust ones.

Thus, for a war to be defined as just, it must be declared by a legitimate authority for a just cause (self-defence) with right intention (for peace) and a fair chance of achieving the goal. The war must be declared as a last resort, and the harm caused by it must not be greater than the good sought. 

Jus in bello governs the conduct during the war. It requires that civilians must be protected, and force must be used when necessary without causing disproportionate harm. A number of authors have also introduced a third component in the just war theory – jus post bellum or justice after war.

Revisionists critique 

Although the just war tradition is seen as a valuable tool for thinking about the morality of war, one of the most dominant traditions in international relations – realism – prioritises realpolitik and the pursuit of power over morality.  

Therefore, such moral scepticism is seen as presenting a direct and immediate challenge to just war thinking, argues David Fisher in his book Morality and War: Can War be Just in the Twenty-first Century?. 

At the same time, revisionists like Jeff McMahan and David Rodin have raised several questions, including the moral equality of combatants and their moral duties to one another. For instance, soldiers fighting on either side of the war are treated as legitimate targets by both traditionalists and international law, and are therefore entitled to moral protection. 

But revisionists argue that soldiers fighting for an unjust cause and posing unjust threats are not entitled to moral protections. In addition, the changing nature of warfare and the emergence of weapons of mass destruction complicate the principles like proportionality, distinction, just cause, and reasonable prospects of success of the just war theory. 

For instance, the NATO’s campaign in Kosovo, the US invasion of Iraq, the Israel-Palestine war and the ongoing US-Israel war against Iran invite intense debate about the principles of just war theory. Nonetheless, the theory provides a robust and indispensable guide for addressing the security challenges of the twenty-first century, says Fisher.  

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