If there is any common thread between the great U.S. foreign policy mistakes of the last several decades—the Vietnam War, the forever war in Afghanistan, the second Iraq war, and the Libya intervention—it is this: they were all wars of choice. We can intelligently debate the merits of them all, we can examine the ways they were conducted once combat operations began, but they were all started on the passionately articulated positions that they were vital to our national interests.

Hindsight tells us otherwise. We now know the hefty sacrifices in lives, treasure, and national confidence from those wars were historic mistakes that cry out to never be repeated. And yet the siren song of unnecessary conflict has made a carefully crafted comeback, at least if you listen to the rhetoric coming out of the White House these days. And this time, not only could trillions of dollars be lost on another war, but something even more financially costly could come to pass: the greatest nation building project our country will ever undertake. To make matters worse, millions of people, including millions of Americans here in the homeland, could lose their lives.

I can only be talking about a war of choice with North Korea. As someone who has studied the issues of war and peace with the hermit kingdom for almost a decade, I speak with some experience. I have waged countless fictional wargames across the Korean Peninsula and for years have worked and spoken with many past and present Pentagon and intelligence officials on this critical issue. Speaking for myself, the evidence overwhelmingly points to a disaster of unimagined scale and scope if the Trump administration decides to attack the portly pariah of Pyongyang. To be blunt, we run the risk of opening a Pandora’s box armed with a nuclear fuse.

Looking into the Abyss

While there are countless potential pathways to war—some sort of accidental missile mishap, North Korea deciding to strike preemptively, Seoul retaliating for an act of violence, or terrorism by Pyongyang—the most likely way a war could begin remains a unilateral U.S. strike to degrade or destroy North Korea’s nuclear and/or missile facilities.

There is ample evidence to suggest that such a strike is being seriously contemplated at the highest levels of the U.S. government. From comments by National Security Advisor H.R. McMaster that North Korea is not deterrable to what seems like almost daily hawkish remarks by UN Security Council Ambassador Nikki Haley and Director of the CIA Mike Pompeo to White House ally John Bolton’s calls in conservative media to consider the “military option,” there beats an ever-present drum that sounds far too similar to what preceded past wars of choice.

A basic outline of how such a strike would be conducted is not hard to surmise. U.S. forces—under pressure from reports that say they have only a three-month window to attack or face a North Korea able to strike the West Coast—begins assembling its forces. Ammunition, already being stockpiled on the island military outpost of Guam, begins growing exponentially. U.S. aircraft carrier battle groups, nuclear attack submarines, and conventionally armed ballistic missile nuclear submarines move into position off the Korean coast. B-1 Bombers as well as B-2, F-22, and F-35 stealth aircraft move into position across the region. The goal seems simple: attack North Korea’s nuclear and missile arsenal, research facilities, known locations of key scientists and personal—anything that helps Pyongyang develop, deploy, or advance its nuclear weapons and missile programs.

How Would North Korea Respond?

So-called experts who clamor for the military option seem to make their arguments in isolation, as if North Korea would simply take punishing U.S. air and naval strikes on the chin and accept defeat. Oh, no. Pyongyang, due to considerations of regime survival—its stated reason for having a nuclear weapons program in the first place—would respond. Assuming Kim Jong-un does not launch his own preemptive attack after seeing the buildup of U.S. forces, Pyongyang would have many vectors on which to pursue a counterattack.

Lowest on the escalation ladder would be a massive artillery and missile strike on the 25 million metro residents of Seoul, one of the most widely cited reasons the Clinton administration in 1994 decided not to attack Kim Il-sung’s nascent nuclear program. While estimates vary on how deadly such a strike would be—we know Kim’s artillery is not in the best mechanical shape and its crews may lack top-tier training—just several hits on downtown Seoul, destroying one more skyscrapers, would cause a mass panic on the scale of 9/11. Or consider five or six large buildings crashing to the ground—not a wild assumption considering North Korea has 11,000 artillery tubes pointed at Seoul as well as advanced missile batteries that fire their ordnance much further. That would provoke an international crisis like none we have seen since 2001. And with social media covering events in real time, the calls for retaliation on a global scale would be impossible to resist.

From here, things could get far worse. Pentagon officials have told me on several occasions that in a military conflict with North Korea our forces would not be able to locate all of Pyongyang’s nuclear weapons. So even after the most massive of strikes on North Korea, Kim would still be left with at least a small nuclear force. That would leave Seoul and Tokyo, with over 60 million people in their metro areas as well as countless U.S. bases in the region, open for potential annihilation.

Then there is the ultimate nightmare: a North Korean nuclear missile attack on the U.S. homeland. While the possibility seems remote at the moment thanks to North Korea still having challenges with the atmospheric reentry technology of its nuclear warheads, some reports offer evidence that Kim could nonetheless hit the American homeland today in a crude fashion. If so, and if U.S. missile defenses are unable to stop such an attack, we could see an American city become atomic ash, with millions of lives lost.

The Day After

To be clear, despite the above omens of what seems like near apocalyptic destruction, America and its allies would win any war against North Korea. What comes after, though, would be the real challenge: a reconstruction and nation building project like perhaps none in all human history.

For starters, North Korea’s 25 million people, or whatever is left of them if nuclear war befalls them, would now need to be cared for medically, economically, and psychologically after decades of brainwashing. Their nation would need to be rebuilt from scratch—that means ports, airports, roads, bridges, tunnels, water-treatment facilities, hospitals, telecommunications networks, and on and on.

Then there is the question of who would rule North Korea when the fighting was over, not to mention the thorny issue of eventual reunification with the south.

Another key matter will be what to do with the armed forces. We know from our experience in Iraq that entirely disbanding a beaten nation’s military is a big mistake, so what to do with all those idle hands?

What about Pyongyang’s elite? Would they be tried for war crimes or would a broad-based amnesty be needed to keep the nation running while only those who committed the most heinous human rights violations would be sent to the Hague?

We also can’t forget about those weapons of mass destruction. Can allied forces find them all before they get sold or used in an insurgency?

And perhaps the most frightening question of all: what to do with the Kim family—yes, we seem to forget, but Kim Jong-un has a wife and children—were they to survive such a war?

An Alternative Path Forward

A war of our choosing against North Korea wouldn’t be anything like the conflicts of the recent past. All those wars had something in common: an enemy that had very little ability to fight back in a way could cause millions of casualties. Today, we face a North Korea that not only can kill millions but potentially target our own nation with nuclear weapons.

So if war is not the answer, what is? I would offer five very basic ideas that could form the basis of an alternative strategy and provide a way out of the current crisis.

Consistency in Messaging is Key. As someone who has worked in foreign policy communications, I would argue that what we say, how we say it, and how consistently we say it matters. It seems certain North Korea is poring over every White House statement, looking for signs of a potential attack or at least what America’s position is—which is very hard to figure out.

Case in point: Secretary of State Rex Tillerson’s bold offer to talk with the North Koreans on December 12 while speaking at a forum here in Washington, D.C. at the Atlantic Council. Tillerson said that America was “ready to talk anytime North Korea would like to talk. And we’re ready to have the first meeting without precondition.” But, just as this White House has done now on several occasions, they seemed later to walk back the statement in a confusingly brief manner that did not directly challenge Tillerson’s remarks but was worded with the clear intent of downplaying them. If I was Kim Jong-un, I was no doubt confused once again where North Korea policy is going—and who is calling the shots.

State our Goals Clearly. Once there is agreement that no one will go off the reservation with their talking points, a clearly defined message can then be articulated. Such a message should be simple: as Secretary of State Tillerson has pointed out, Washington should state that it does not seek regime change. This should be the foundation of any messaging to North Korea as it addresses their greatest fear. From there, the White House should make clear that they will not launch any attack on North Korea unless our allies, military bases, or homeland were attacked first, addressing Pyongyang’s other great concern and hopefully laying the foundation for an easing of tensions.

Offer Open-Ended Talks. The Trump team shouldn’t be afraid to ease tensions with North Korea. They should give Tillerson’s proposal a chance and offer to sit down with Kim’s representatives at any time, at any place, to discuss any issue, without preconditions. This puts the Trump administration in the diplomatic driver seat and once again allays any concerns about a near-term strike or move towards regime change against Kim.

Listen to Our Allies—and China. Throughout this process, Washington needs to take its allies’ and adversaries’ concerns seriously. To be fair, in a war with North Korea, Japan, South Korea, and even China would feel the brunt of the conflict and its aftermath far more than anyone else. We need to lead from the front on this critical issue, doing all we can to create the conditions for talks and an eventual settlement the region can live with. At the same time, our allies and even regional competitor’s concerns must be taken seriously. Not doing so, or ignoring their ideas if and when talks do occur, will only invite problems in the future.

If All Else Fails, Contain and Deter. The good news is that no matter what happens, the U.S. and its allies have a roadmap to deal with North Korea: it’s called containment followed by deterrence.

Washington knows what to do when a nation that has very different and very threatening national security goals builds nuclear weapons. Remember that Joseph Stalin, a butcher who killed millions of his own people, pursued and built nuclear weapons, while Mao Zedong—who, according to one estimate, is responsible for the deaths of as many as 45 million people in just one four-year span—also started a nuclear program. Clearly both were bigger existential threats to U.S. goals than today’s North Korea—a nation with an economy the size of Vermont that can’t even adequately feed its own people—yet neither was attacked by the U.S.

Sometimes, we must choose between bad options, and a war with North Korea—it must be made crystal clear—is a choice we would regret for generations. Thankfully, it is not a choice we must make.

Harry J. Kazianis is director of defense studies at the Center for the National Interest and executive editor of its publishing arm, The National Interest. Previously, he served as editor of The Diplomat, a fellow at CSIS, and on the 2016 Ted Cruz foreign policy team.