The usually calm and cool spokesman John Kirby became uncharacteristically emotional when discussing Russia’s latest offensive. “It’s hard to look at what he’s doing in Ukraine, what his forces are doing in Ukraine, and think that any ethical, moral individual could justify that… It’s difficult to look at the…” Kirby said, before taking a moment to gather himself, “Sorry. It’s difficult to look at some of the images and imagine that any well-thinking, serious mature leader would do that. So I can’t talk to his psychology, but I think we can all speak to his depravity.”

With this seemingly genuine response, Kirby reflects well on Americans and illuminates something of the Western way of war.

The West’s observance of the Just War Tradition (JWT) best characterizes its way of war. And the JWT has animated international positive law as well as the laws of war that we teach our warfighters. Thus, it is not some irrelevant abstract theory; it is still relevant today and informs US officials, even if through their consciences rather than consultations of the laws of war manual. (That doesn’t mean we always get its application right, of course, more on that later.)

From ancient to modern times, the question of when and how one might rightfully engage in warfare has been a subject of statesmen, philosophers, and religious leaders. These great thinkers have agreed on broad principles even while adding or dissenting in some fashion to a body of scholarly work. This body, which draws from the natural law as well as Jewish and Christian texts, is best understood as a tapestry of Western thought that forms the Just War Tradition.

Although the JWT does not provide a precise prescription, it offers the most “relevant principles that are intelligible, generalizable, and capable of consistent application,” as Ralph Potter nicely stated.

Lest critics or skeptics think this talk of morality in warfare is the stuff of idealism, to the contrary, those who hold to the JWT do so because they know that in this world nations will always distrust one another and must arm themselves in defense. The realist knows that the best guarantor of the security of its peoples does not lie in an international governing body—no, that is the stuff of utopia and will not come to pass in this world. The best guarantor of the security of a nation’s people is the government and all of its tools of statecraft, including the “sword”—that is, its military.

Thus, the JWT is precisely for the realist who seeks to navigate the horrors of war justly. This brings me to the main point—a just government protects the innocent, punishes the evildoer, and restores a just peace. What Russia is doing flies in the face of this moral imperative. It uses weapons to cause civilian casualties, and bombs cities where civilians are hiding and trying to survive. It targets areas where it knows the elderly, mothers, and children are trying to escape.

But the skeptic still might respond, Didn’t the United States not so long ago kill civilians in a drone strike in Afghanistan? Yes. As far as we know, not a single enemy combatant was killed in that strike. In a tragic error almost certainly the fault of bad intelligence, hasty decision-making on the part of the Biden administration, and a slew of other military and civilian leadership decisions, the United States killed politically innocent men and children.

We can all collectively see that this drone strike was terrible because it did precisely what we train our leaders and warriors not to do. There should be ramifications for that; senior leaders should be held to account. When we do not hold them to account, we run the risk of causing our warfighters to doubt their noble mission to protect the innocent and the American way of life. Or worse, they can suffer moral injury or feel guilt that is not theirs to bear. But there are other grave and wide-reaching effects: American citizens and allies become skeptical or even cynical of the American-led West.

So while it is important to maintain a moral clarity about the nature of the adversary, whether Russia or ISIS or the Taliban, it is also important that we hold ourselves to those JWT principles as reasonably as we can, and hold political and military leaders accountable when they fall short.

While America has not always followed JWT perfectly, Kirby’s correct description of Putin is important. The Putin regime is prosecuting a barbaric and unjust war and so far shows no signs of wanting a return to peace. While the Biden administration is right to side with Ukraine and provide arms to help them defend themselves, the kinds of arms they are providing are not enough to permit the Ukrainians to go on a much more lethal counter-offensive. This must change so that Ukraine can force Putin to want the war to end, because only then is a just restoration of peace possible.