Larry Downing / Reuters

The week of the 15th anniversary of the Iraq War is ending. If past anniversaries are any guide, as that period closes, so will end the brief moment of reflection on the causes and consequences of the war—the mistakes that led to it and the damage that followed. All these years later, we’re still grappling with how it began, but that shouldn’t overshadow questions about how the justice of the cause evolved over the years that followed.  

Andrew Exum, a former Army Ranger who served in Iraq in the first year of the war, wrote achingly of his dismay at its tortured beginning. He sympathized with the moral case for removing a bloodthirsty dictator. But, as he watched the war’s execution, he “developed what will probably be a lifelong suspicion of any moral justifications for initiating a conflict,” he wrote. And yet Exum came back to Iraq years later, as a senior government official working on the effort to uproot the Islamic State—a cause that, presumably, would prove more just.

There’s a broader sense of moral confusion about the conduct of America’s wars. In Iraq, what started as a war of choice came to resemble much more a war of necessity. Can a war that started unjustly ever become righteous? Or does the stain permanently taint anything that comes after it?

The answers to these questions come from the school of philosophy called “just war” theory, which tries to explain whether and when war is permissible, and under what circumstances. It offers two big ways to think about the justice of war. One is whether it’s appropriate to go to war in the first place. Take North Korea, for example. Is there a cause worth killing thousands—millions—of North and South Korean civilians over? Invoking “national security” isn’t enough to make a war just. Kim Jong Un’s nuclear weapons pose an obvious threat to South Korea, Japan, and the United States. But that alone doesn’t make war an acceptable choice, given the lives at stake. The ethics of war require the public to assess how certain it is that innocents will be killed if the military doesn’t act (Will Kim really use his nukes offensively?), whether there’s any way to remove the threat without violence (Has diplomacy been exhausted?), and whether the scale of the deaths that would come from intervention is truly in line with the danger war is meant to avert (If the peninsula has to be burned down to be saved, is it really worth it?)—among other considerations.

The other questions to ask are about the nature of the combat. Are soldiers taking care to target only North Korea’s military? Once the decision has been made that Kim’s nuclear weapons pose an imminent threat, hypothetically, that still wouldn’t make it acceptable to firebomb Pyongyang to turn the population against him. Similarly, American forces could not, say, blow up a bus full of children just because one of Kim’s generals was trying to escape on it.

But that’s an assessment of a hypothetical war from one moment in time. Looking back at Iraq over many years presents a different challenge. It requires accepting that judgments about the morality of a war—even one that began under circumstances as contested as those of the Iraq War—need to change as the circumstances do. Jeff McMahan, a professor of moral philosophy at Oxford University, has spent his career looking at questions like these. “The moral nature of a war can change,” he told me.

The two sets of questions about how to judge war are built into international and domestic law, and largely mirror how war is debated. A public debate about the need to go to war—think of Colin Powell’s presentation to the U.N. Security Council—gave way to questions about the conduct of U.S. forces once the war began. But the division of ethical principles into sets of questions that apply at various times to different parts of war is confusing, perhaps needlessly so, according to McMahan. “Because conditions are continually changing, whether it’s permissible to continue to fight is always an open question. And therefore I think of jus ad bellum [questions about the initiation of war] not as a set of principles to check when initiating a war, but as a set of principles that has to be reapplied continually.”

To put it another way, the justice of war can change as the strategy does. Those big questions about whether the right cause can be pursued at the appropriate cost apply not just at the start of a war, but for its duration. This has surprising effects when you think through the course of the war in Iraq. As the conflict entered its bloodiest, most sectarian phase—from roughly 2006 on through the Surge—Americans came to believe that the use of force in Iraq was wrong, according to Pew. (A plurality has, for the most part, continued to believe that ever since.) Paradoxically, at that time, the intervention may have had a stronger case than when the war began.

McMahan explained: “There was more of a case for an American occupation of Iraq after the United States had effectively destroyed any kind of security institutions there and had disbanded the army and kicked the Sunnis out of power. It left a real vacuum in the kind of political, social, and security institutions in the country. Somebody had to do something about that to protect people from predators and to protect people from violence from the other sects within the country.”

The bull had destroyed the china shop. Yet only the bull could fix it. More than that, argues the ethicist Gerard Powers, it would have been wrong for the United States to withdraw at that point. One might say, looking at the situation now, “Let Iraq and Syria be torn apart by their ancient hatreds. But that would be shirking our moral obligation, because the United States became, voluntarily, very much a part of those ancient hatreds. So I think the argument leads to a strong sense of moral responsibility to do something to address the problem.” As McMahan pointed out, it would have been better for the United States to pay for neutral peacekeepers, but that was never a realistic possibility.

There is no redemption at the end of this kind of continuously applied moral theory; it ends, hopefully, with simply the fewest number of civilians killed needlessly. But there is a constant chance to do better, to pay for one’s past mistakes. America, as a democracy with a military obsessed with its own failures, is better suited than most countries to take those chances. It can change course midstream and improve upon its moral failures. By contrast, once Russia intervened in Ukraine or Syria, the moral course of those wars was set. There is no chance that war-weary Russians will vote out their president, in the way that Americans chose pro-withdrawal Barack Obama over the hawkish Hillary Clinton and John McCain in 2008.

But with those chances to do better come chances to renew the chaos and injustice. Just look at Afghanistan. An initial cause that could hardly be more just—defending against further terror attacks and bringing the attackers to justice—seems to have little to do with the mission Americans and their allies are still fighting nearly two decades later. The questions that this raises about the larger goals Americans are fighting for aren’t only debates about strategy—they’re also tied to judgments about whether the cause is even a just one any more.

And they still apply to the conflicts in the Middle East that have come about since 2003. Combat in Iraq itself is largely over, but the country is far from stable. Americans are actively fighting in Syria, where it is difficult for the free press to hold the government’s feet to the fire. Out of the public eye, a fight that went wrong there would be harder to correct. The fight against ISIS has a clearer moral rationale than the initial invasion of Iraq, but there’s no guarantee it will stay that way.

Reasonable people can argue that the fight against ISIS is separate from the original war in Iraq, with a separate justification. One of these people is Michael Walzer, the dean of just war theorists and a professor emeritus at the Institute for Advanced Study. In an email, he wrote, “There really were two distinct decisions—to go to war in 2003 (which I thought unjust) and to join the fight against ISIS (which I thought justified).” But Walzer agreed in principle that one “can imagine a single war that changes its moral course and requires changes in our judgements.”  

That’s why the return of the architects of the worst phases of the Iraq War to positions of power should give us pause. In firing his national security adviser, President Donald Trump has traded H.R. McMaster, who commanded American forces in Iraq during the war’s worst period and has closely studied the U.S. military’s worst mistakes, for John Bolton, who helped shape the initial invasion and still strongly supports the decision to go in. The justice of America’s wars has shifted. It could change again. And it shouldn’t take an anniversary to reassess them.

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