Opinion – Donald Trump vs Pope Leo XIV: Just War and the Emperor’s New Clothes

Just War theory has been at the heart of discussion of the US/Israel war on Iran over the last couple of weeks. This is great for theorists and students of international relations because Just War has been, and still is, central to the conception of international order. So much so that practically every leading philosopher, jurist and theologian has written on it. Just War theory has a long history, going back to the Ancient Greeks (Aristotle, 4th Century BCE) and the Romans (Cicero, 1st Century BCE) as a moral and ethical compass, seeking to limit and to regulate war and its practice. The basis of the international law of war is held to stem from these pre-modern beginnings, mediated and given additional content by Saint Augustine (4th Century) and Saint Thomas Aquinas (13th Century).

Today, Just War theory is normally reduced to a number of questions, divided into three temporal concerns: Jus ad Bellum (justice of war) including considerations of just cause, legitimate authority, right intention, last resort, proportionality and probability of success; Jus in Bello (justice in war) including the need to discriminate between civilian and military targets, proportionality to objectives and military necessity; and Jus post Bellum (justice after war) requiring a just peace settlement, reconstruction and holding perpetrators to account.

But why is Just War in the headlines now? There are a number of reasons for this return to a focus on Just War. Firstly, the breakdown of the liberal international order has left the United Nations toothless in the face of aggression by major powers. Secondly, it seems that domestic political orders are also lacking the capacity to hold leaders to account, a problem across the board, from Putin’s Russia and Trump’s America to Netanyahu’s Israel. Today it seems that international conflicts are driven as much by personalities and individual concerns as the strategic concerns of realpolitik. However, there is also a third reason for Just War to be at the heart of controversy, this is the one that I think is the most interesting. The crisis within the contemporary Christian order.

This may seem counterintuitive, for many it appears that Christianity is gaining in importance in domestic and international politics in the absence of traditional political loyalties and rise of more speculative, spiritual approaches to our world of crisis and contingency. However, the discussion of Just War brings to the surface the role that Christianity plays, still today, in upholding the legitimacy of the international order. It was Just War theory that helped to cohere and rationalise international order as a universal ethical concern at the same time as Christianity provided the framework of moral legitimation for western coloniality. This synergy between religion and politics was made possible through the reconstruction of Christianity for the modern era as the religious exception.

From the time of Kant and other Enlightenment philosophers, Christianity was remade for the modern colonial era as the religion compatible with universality, with reason and rationality and with secular modes of governance. Christianity could inform the rise of colonial modernity, providing ethical and moral legitimacy to an order that sought to constrain ‘war’ – conflict between European powers – but to enable extreme modes of colonial violence, genocide, dispossession and ecological destruction across the Global South. Christianity was the exceptional religion because it could present itself (like early modes of international law) as above petty material conflicts and particularist interests. Christianity provided the unmarked position of universality (of White Supremacy) while other world religions, such as Judaism, Islam, Hinduism and Sikhism were seen as too tied to limited and partial interests.

As J. Kameron Carter writes in Race: A Theological Account, the role of religion, specifically that of modernised Christianity, in the construction of the liberal political imaginary, and of understandings of both domestic and international political order, is rarely given its due. In large part this is because Christianity as a mode of discursively constructing a global or universal ethical framework, while particularising other ethical framings, works in the background. While the other world religions have beliefs that need to be respected, Christianity is held to be the only religion that is ‘beyond belief’, held to have a universal rationalist detachment from particularist or vested interests.

Just War’s centrality to discussion of the US/Israel war on Iran is in large part due to the current schism in the Christian world. This schism reached its highpoint in the direct confrontation between JD Vance, the US Vice-President and Pope Leo XIV over the nature of Just War. This was in response to the Pope’s rebuttal of US Defence Secretary Pete Hegseth’s claim that people should pray to Jesus to support the US war effort and in US President Donald Trump’s AI generated social media post, portraying himself as a Jesus-like figure, and his earlier direct attack on the Pope’s intervention in political issues. The question at the heart of this schism is: ‘Is God on the side of America?’.

The Pope’s apparent inability to take the side of Christian America against an Iranian state, portrayed as the chief sponsor of Islamic terrorism and violence, brings this schism into the open. In this way, the friction between Trumps’ US foreign actions and the Pope reflect the similar friction between Trump and the other institutions of the old international order, including the United Nations. While the Pope seeks to uphold the imaginary of a higher international order above the politics of states – the universal exceptionalism of Christianity, above the petty materialist concerns of earthly politicians – the rise of Christian nationalism in the US threatens to undermine Christianity’s exceptional status as the religion of modern universalism.

There is a certain irony in Trump’s AI image of himself portrayed as a modern-day Jesus. I’m sure many would like to imagine that this will come back to haunt Trump exposing him as lacking, once again, any respect for others and perhaps even questioning his mental state. This may well be the case. However, the important point to note is that it is not only Trump that risks being exposed here. It is also the Pope that risks being called out as the emperor without any clothes if the schism with the US establishment brings into full light the unstated universalist assumptions that enabled modern Christianity to provide the moral underpinning of international order.

Further Reading on E-International Relations

Great Power Rivalry and Israeli Selective Neutrality: ‘Walking Between the Drops’

Opinion – The Pope’s Apology for Indigenous Residential Schools

The Mexicali Committee in Solidarity with Palestine as a Case of Decolonial Praxis

United Moderate Religion vs. Secular and Religious Extremes?

The Medieval Foundations of the Theory of Sovereignty

Iraqi Kurdistan and the Failure of Capitalizing Kurdish-Israeli Relations

David Chandler is Professor of International Relations at the University of Westminster, London. He edits the open access journal Anthropocenes: Human, Inhuman, Posthuman. His recent mongraphs include Race in the Anthropocene: Coloniality, Disavowal and the Black Horizon (with Farai Chipato, 2024); The World as Abyss: The Caribbean and Critical Thought in the Anthropocene (with Jonathan Pugh, 2023); Anthropocene Islands: Entangled Worlds (with Jonathan Pugh, 2021); Becoming Indigenous: Governing Imaginaries in the Anthropocene (with Julian Reid, 2019); and Ontopolitics in the Anthropocene: An Introduction to Mapping, Sensing and Hacking (2018).


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