By Michael Crompton

Just war theory is a doctrine that is meant to discern if a conflict is morally justified. This essay will primarily focus on intra state wars and humanitarian interventions in relation to the theory. It will begin by examining whether the criteria of Just war theory are aligned with the ethics of modern liberal states. It will go on to outline how the changing nature of the international order and conflict have led to other doctrines within international relations, such as responsibility to protect, having more utility than Just war theory. During the course of this article I will also question whether the ambiguity of the theory leaves it with little relevance. Just war theory is certainly not as useful as it once was in judging the morality of warfare, but the extent to which it is relevant to the ethics of international conflict remains contested.

Jus ad bellum forms part of the criterium for Just war theory. It can be used to determine whether a nation state has just cause to go to war, however, it is not entirely aligned with common liberal principles. One of the key points in the criteria is that one must have right authority whereby only sovereign states can legitimately declare war (Shapcott, 2014). This statist notion makes any insurgency illegitimate and unjust, but in practice this is a very hard position to justify (Hehir, 2013). Kosovo stands as an example in which the insurgency would be considered unjust, yet an intervention that assisted the insurgency has been declared legitimate by the United Nations (UN). This suggests that the non-state forces were in fact more just than the state. Moreover, in modern liberal states imperialism is considered immoral and self-determination a moral right, as such armed resistance to imperial rule is usually considered justified.  Therefore, there is clearly a strongly supported argument toward this section of Just war theory remaining outdated as it is somewhat incompatible with liberal ethics. As a result, this reduces its relevance to ethics of international conflict.

However, the majority of debate as to moral legitimacy of a conflict still remains focused around parts of jus ad bellum.  The House of Commons debate on whether to take action against Assad in Syria in 2013  was heavily rooted in just war theory:  Miliband questioned whether there was ‘a reasonable prospect of success’ (Miliband, 2013), as well as ‘prospects for peace’, while Arbuthnot (2013) brought attention to proportionality. These are all key parts of the jus ad bellum section of the just war theory and this is no coincidence. Many of the debates around almost all modern conflicts tend to assess whether certain criteria of just war theory have been fulfilled. Thus, vast sections of just war theory are not only compatible with the ethics of liberal states but are intertwined into the discourse around the moral legitimacy of international conflict.

However, as a holistic theory or framework for approaching the debate as to whether a conflict is justified it is no longer suitable. Just war theory was largely developed to tackle conflicts between nation states (Lazar, 2016) and it does not consider international law and institutional obligations. This raises several issues, for instance, the North Atlantic Treaty Organisation (NATO) requires member states to respond if one state invokes the collective security pact (article 5). It is unclear if, when  this was invoked in response to 9/11 (NATO, 2016), any treaty obligations constituted a just cause.

Furthermore, in this case another central problem of Just war theory is that when the the aggressor is a non-state actor in another state the theory fails to provide an appropriate course of action.  Traditionally such action has been viewed as self-defence and would give the state just cause to go to war under Just War Theory (Shapcott, 2014), but crucially if such action involves the invasion of a state’s territory that is not aggressing on the state, justification on the basis of self defence becomes an even more contentious issue. Generally speaking just war theory has little to contribute to discussion in regards to the US led war on terror when the threat of attack appears to be constant. This highlights a recurring point that military intervention justified through self defence lacks quantifiable distinction and is open to be misunderstood and abused, showing a weakness of the just war criteria.

In spite of its flaws Just war theory and its principles remains relevant today  primarily due to  its inherent flexibility. Take the principles of just cause, right intention and just conduct. In the early days of the tradition the crusades would have been seen as war with a just cause (Hehir, 2013) however, today holy wars are largely seen as illegitimate and the crusades are seen as some of most horrendous moments of European history. Right intention is by its nature impossible to determine (as motives are hard to discern), and just conduct (a tenant of jus in bello) is almost constantly in flux. While British ground troops have strict rules of engagement, essentially only being allowed to fire upon a person when they see a weapon (Owen, 2012), unmanned drones can attack human targets which are not currently in combat  or posing an immediate risk to life (Boyle, 2013). Just War Theory cannot determine whether either tactic constitutes just conduct. In order to apply Just War Theory one must decide if one, neither or both these approaches represent just conduct in war. This is the same with all the criteria of just war they are inherently ambiguous and malleable, therefore the judgement of whether a war is just according to the theory is entirely subjective based on the interpretation of each criterion making it near useless in terms of a checklist approach to legitimising conflict.

In recent times the doctrine of responsibility to protect has proven itself more useful for thinking about the ethics of many international conflicts. However, whereas Just war theory is a theory meant to apply to all conflicts, responsibility to protect (R2P) is a specific legal doctrine which applies only when there is evidence of genocide, crimes against humanity, war crimes or ethnic cleansing. It raises several key points in which it deals with the problems of Just War Theory. Firstly, under this doctrine sovereignty comes with responsibility; a sovereign who commits these crimes or lacks the capacity to prevent them has their sovereignty transferred to the international community (Hehir, 2013). As a result, this allows for one state to target war criminals within the boundaries of another state regardless of whether the criminals are state or non-state actors. Secondly, the doctrine explains that states should, if possible, seek a mandate from the UN Security Council (Barnet, 2016) before engaging in a military intervention. The original International Commision on Intervention and State Sovereignty report (from which the doctrine originates) also suggests that military intervention can be legitimate (but still illegal) if they cannot, provided that the intervention has followed the other criteria of R2P. However, due to its specificity it has only been used to justify military action against a regime once (although the responsibility to protect section of the doctrine has been used more frequently). As such, R2P deals with one of the major issues of just war theory as it takes account of international law and attempts to balance it with moral obligations.

It is important to note that R2P is heavily rooted in just war theory. It asks for a just cause (i.e. stopping one of the four crimes mentioned earlier), under responsibility to prevent it heavily focuses on diplomatic solutions and military intervention should only be used as a last resort (Hehir, 2013). Furthermore, it also suggests what is just after peace has been achieved under responsibility to rebuild (mirroring jus post bellum). Therefore, while the changing nature of combat and the ambiguity of the initial theory which makes just war tradition very limited as a tool today, its content is very useful for forming the tools in analysing the ethics of an international conflict.

In conclusion, there are some criteria within Just war theory that are no longer compatible with the ethics of liberal states. However, many of its criterion are still the central pillars around which the debate on international conflict takes place. Furthermore, just war theory lacks capacity to judge conflicts against non-state actors (e.g. the war on terror) and humanitarian interventions. Despite this, tools that are more useful for discussing these situations incorporate parts of just war theory. Therefore, the content of just war theory is certainly relevant to thinking about the ethics of international conflict. However as a holistic approach to judging the morality of a conflict it is no longer suitable and other tools such as Responsibility to Protect that are more specific must supplement it.

Reference List

Arbuthnot, J. (2013) House of Commons Records. Available from: [Accessed 03/01/2017]

Barnet, M. (2016) Duties beyond borders. In Dunne, T., Hadfield, A.  and Smith, S., eds. (2016) Foreign Policy: Theories, Actors, Cases. 3rd ed. Oxford: Oxford University Press, pp. 242-259.

Boyle, M. J. (2013) The costs and consequences of drone warfare. International Affairs, 89, pp.1–29.

Hehir, A. (2013) Humanitarian Intervention: An introduction. 2nd ed. Basingstoke: Palgrave Macmillan

Lazar, S. (2016) The Stanford Encyclopedia of Philosophy: War.  Available from: [Accessed 03/01/2017]

Miliband, E. (2013) House of Commons Records. Available from: [Accessed 03/01/2017]

NATO. (2016) Collective defence – Article 5. Available from: [Accessed 03/01/2017]

Owen, J. (2012) British soldiers resort to ‘baiting’ Taliban to beat rules of engagement. The Independent [online] 22 August. Available from: [Accessed 03/01/2017]

Shapcott, C. (2014) International Ethics. In Baylis, J., Smith, S. and Owens, P. (2014) The Globalisation of World Politics: An Introduction to International Relations. 6th ed.  Oxford: Oxford University Press, pp 199-209.