Christopher Nolan’s blockbuster film, Oppenheimer, has reignited the decades-old debate over whether the United States was justified in using nuclear weapons against Japan during World War II. A legal corollary to that debate is whether Just War theory and doctrine remain relevant within the realm of international law and national security. The United States has long acknowledged Just War principles under the twin concepts of jus ad bellum and jus in bello, and recent events suggest that those principles are, indeed, as relevant and applicable as ever.

Shortly after the start of the Korean War, the Truman Administration published a report that concluded, in part:

[The] side of the world, to which we belong, holds to the idea of a moral law which is based on religious convictions and teachings. The fundamental principles which give our democratic ideas their intellectual and emotional vigor are rooted in the religions which most of us have been taught. Our religious convictions continue to give our democratic faith a very large measure of its strength.

The nature of warfare is that it is ever evolving, at least when it comes to the instruments of war, as Oppenheimer so vividly depicts. But for those who hold to the idea of a moral law, the “fundamental principles” that determine when and how to fight should remain fixed.

Just War theory posits that a state must have a moral justification for using force, and that any such use must be for a legitimate purpose and pursued only by means sufficient to achieve that purpose, and no more.

To that end, U.S. Representative Jerry McNerney (D-CA-9) recently introduced House Resolution 1009 “regarding the consideration of ‘Just War’ principles prior to any vote with respect to a declaration of war or an authorization of the use of military force.” HR 1009 invites the most representative body in our federal government to consider Just War principles prior to authorizing any use of military force. In other words, HR 1009 encourages the United States to subordinate miliary power to politics.

These principles are by no means novel, and they have deep roots within the American legal and military traditions. The international legal community has also long recognized Just War principles. Indeed, the United Nations Charter places explicit limitations on when and how member states may use force.

Some observers and critics suggest that America’s commitment to Just War theory is dormant or even waning. Others suggest that Just War theory is obsolete. But such a conclusion is an overstatement.

In July 2023, the U.S. Air Force Deputy Chief of Staff for Plans and Programs publicly suggested that the United States will use and employ artificial intelligence—yet another evolving instrument of warfare—in a more ethical manner than our adversaries because “our society is a Judeo-Christian society, and we have a moral compass.”

Critics were quick to chastise a uniformed general officer for making such an overt reference to religion. But seizing upon a few choice words misses the forest for the trees. The real issue is that the United States faces numerous adversaries who routinely demonstrate their willingness to use military force without any scruples. As a nation, we have historically been, and must continue to be, different.

A commitment to our Judeo-Christian ethos as a governing paradigm is not merely a luxury, but a necessity if we are to use developing military means in an ethical manner. And although anecdotal, the fact that a top U.S. military officer would make such a statement indicates that Just War theory is not, in fact, obsolete.


As the United States approaches yet another inflection point in its history, perhaps we would do well to give serious consideration to Just War principles as a means of restraining our use of military force in a manner that is morally justified and consistent with longstanding norms.

Note from the Editor: The Federalist Society takes no positions on particular legal and public policy matters. Any expressions of opinion are those of the author. We welcome responses to the views presented here. To join the debate, please email us at [email protected].