Just War on Iran? Trump and America’s Catholics

There are just over 50 million Catholic voters in the United States, and in the 2024 election 59 per cent of them voted for Donald Trump, compared with 39 per cent for the Democratic candidate Kamala Harris. The clash between Mr Trump and Pope Leo risks proving costly for the Republican party, particularly with the midterm elections approaching this autumn.

The US president has accused the pontiff of being “weak on crime”, “terrible for foreign policy” and “too liberal”, even claiming that “if I weren’t in the White House, he wouldn’t be pope” — assertions that resonate with core Maga tropes. Even before the current escalation, Mr Trump’s war against Iran had begun to erode his support. According to a late-March poll, Catholic backing for the commander-in-chief fell below 50 per cent for the first time.

At the heart of the dispute between the Trump administration and Pope Leo XIV lies a theological question. In recent weeks, the pope has repeatedly criticized the US strike on Iran, to which Mr Trump has responded with at times implausible arguments. “I don’t want a pope who thinks it’s okay for Iran to have nuclear weapons,” he said, before adding two days ago: “I’m not fighting with him. The pope made a statement saying Iran can have nuclear weapon.”

Last month, during Easter celebrations, Pope Leo XIV said that God “does not listen to the prayer of those who wage war and rejects it, saying: ‘Even if you multiply your prayers, I will not listen; your hands are full of blood.’” The statement was widely interpreted as a direct and forceful criticism of the Trump administration and its actions in Iran. In the following weeks, the pope reiterated his concerns, culminating in the confrontation of recent days. “I am not afraid of the Trump administration nor of openly proclaiming the message of the Gospel, which is what I believe I must do, what the Church is called to do. We are not politicians, we do not wish to deal with foreign policy in the way he conceives it,” he said while traveling to Africa on his first pastoral mission. “Woe to those who bend religions and the very name of God to their military, economic and political objectives, dragging what is sacred into what is most sordid and dark,” he added from Cameroon.

Paula White, a senior adviser in the White House Faith Office, put it bluntly: “To say no to President Trump would be to say no to God.” More consequentially, vice-president JD Vance argued that the pope should “be careful when speaking about theological matters”, adding that Catholicism contains “a more than thousand-year tradition of just war theory”. Vance, who converted to Catholicism in 2019, often frames Christianity in public and identity-driven terms. He was joined by Mike Johnson, the Speaker of the House and a close Trump ally, who stated: “There is something called the doctrine of just war.” Johnson, a Baptist evangelical, has long advanced an explicitly religious reading of American politics: to what extent does this approach translate into a direct use of the Bible as the ultimate reference for public and legislative action?

Yet the administration’s line is more sophisticated: to challenge the pope on his own terrain. Figures such as Vance and Johnson — alongside a broader circle of staunch Trump supporters — argue that it is not true that God does not hear the prayers of those who wage war, as Leo suggests, because the Catholic Church itself has developed a doctrine of just war that, in certain cases, justifies the use of force.

That doctrine does indeed exist, with deep historical roots. From St Augustine in the fourth and fifth centuries onwards, just war theory has often been stretched to justify wars of aggression and conquest. It is worth recalling that Robert Francis Prevost is an American Augustinian — an order that blends monastic contemplation with active engagement in the world — meaning that the question of just war touches the formative roots of Pope Leo himself. Yet it is primarily from the 20th century onwards that the doctrine has been codified in a more stringent manner.

According to the Catechism of the Catholic Church — the official articulation of Catholic principles — war is legitimate only when it is defensive, a response to “lasting, grave and certain” damage, and when “all other means of putting an end to it have been shown to be impractical or ineffective”. Moreover, war must not produce “evils and disorders graver than the evil to be eliminated.”

Does Mr Trump’s war against Iran meet these criteria? Although the US administration has sought to frame it as a response to Iran’s nuclear threat — which exists, but is neither immediate nor resolvable solely through military means — or as a way to protect a civilian population brutally repressed by the regime, these elements appear insufficient to meet the stringent requirements of just war doctrine.

The response of the US Conference of Catholic Bishops is similarly skeptical. Bishop James Massa, chairman of the Bishops’ Committee on Doctrine, noted that “for over a thousand years, the Catholic Church has taught just war theory, and it is that long tradition the Holy Father carefully references in his comments on war.” Citing the Catechism (no. 2308), he added that a nation can only legitimately take up the sword “in self-defense, once all peace efforts have failed.” The implication is clear: the pope is not offering a political judgement, but invoking a doctrinal standard — and, in doing so, setting the terms of the debate.

It is precisely this shift in terrain that helps explain the broader clash. As Father Antonio Spadaro, under-secretary of the Vatican’s Dicastery for Culture and Education, put it in the Financial Times, Pope Leo offers “a counter-narrative” to Maga-style national Catholicism. “He is implicitly recalling another America,” Spadaro says — “the America that, in its better moments, was a moral force in the world: the America of leadership grounded in legitimacy rather than coercion.”

From here, the divide becomes political as much as theological. US Christian conservatives typically view sexuality and family values as the primary sphere in which religious beliefs should prevail. Pope Leo, however, also sees economic inequality and social justice as central moral questions — and above all regards war and peace as the most urgent ethical issues of the present moment. It is within this divergence that a deeper fracture emerges: can the Maga narrative of “just war” continue to hold together the Catholic electorate around Mr Trump?

“We can no longer think of war as a solution, because the risks will probably always be greater than the supposed benefits attributed to it. In the face of this reality, it is very difficult today to uphold the rational criteria developed in past centuries for speaking of a possible ‘just war’,” wrote Pope Francis in his 2020 encyclical Fratelli Tutti.