Late last September, I moderated a discussion about North Korea with retired Navy Adm. James Stavridis, whose 37-year military career included a stint running NATO, and Michèle Flournoy, the No. 3 official at the Pentagon during the Obama administration, who has helped shape US policy toward North Korea since 1993.

It was a chilling conversation. Stavridis said there was at least a 10 percent chance of a nuclear war between the US and North Korea, and a 20 to 30 percent chance of a conventional conflict that could kill a million people or more. Flournoy said President Trump’s tough talk about North Korea — which has included deriding Kim Jong Un as “Little Rocket Man” and threatening to rain “fire and fury” down on his country — made it “much more likely now that one side or the other will misread what was intended as a show of commitment or a show of force.”

The Trump administration, for its part, seems more confident in its ability to manage North Korea with precision. National Security Adviser H.R. McMaster is pushing something known inside the White House as a “bloody nose” strategy of responding to a North Korean provocation with a set of limited US military strikes. McMaster seems to believe that Kim would passively absorb the attack without hitting back and risking all-out war.

I covered the Iraq War from Baghdad. I saw the aftermath of a conflict built atop sunny scenarios and rosy thinking. I’ve seen the cost of wars that the American people were not prepared for and did not fully understand. The rhetoric around North Korea is raising those same alarm bells for me. For all the talk of nuclear exchanges and giant buttons, there has been little realistic discussion of what a war on the Korean Peninsula might mean, how it could escalate, what commitments would be required, and what sacrifices would be demanded.

So I’ve spent the past month posing those questions to more than a dozen former Pentagon officials, CIA analysts, US military officers, and think tank experts, as well as to a retired South Korean general who spent his entire professional life preparing to fight the North. They’ve all said variants of the same thing: There is a genuine risk of a war on the Korean Peninsula that would involve the use of chemical, biological, and nuclear weapons. Several estimated that millions — plural — would die.

Even more frightening, most of the people I spoke to said they believed Kim would use nuclear weapons against South Korea in the initial stages of the fighting — not just as a desperate last resort.

“This would be nothing like Iraq,” Flournoy told me. “It’s not that the North Korean military is so good. It’s that North Korea has nuclear weapons and other weapons of mass destruction — and is now in a situation where they might have real incentives to use them.”

The experts I spoke to all stressed that Kim could devastate Seoul without even needing to use his weapons of mass destruction. The North Korean military has an enormous number of rocket launchers and artillery pieces within range of Seoul. The nonpartisan Congressional Research Service estimates that Kim could hammer the South Korean capital with an astonishing 10,000 rockets per minute — and that such a barrage could kill more than 300,000 South Koreans in the opening days of the conflict. That’s all without using a single nuclear, chemical, or biological weapon.

And retired South Korean Gen. In-Bum Chun, who spent 40 years in uniform thinking about a confrontation with North Korea, underscored that Kim also has a different kind of weapon: 25 million people — including 1.2 million active-duty troops and several million reservists — who have been “indoctrinated since childhood with the belief that Kim and his family are literal gods whose government must be protected at all costs.”

“You’re talking about people who have basically been brainwashed their entire lives,” Chun said. “It would be like what you saw on Okinawa during World War II, where Japanese civilians and soldiers were all willing to fight to the death. This would be a hard and bloody war.”

What follows is a guide to what a conflict with North Korea might look like. War is inherently unpredictable: It’s possible Kim would use every type of weapon of mass destruction he possesses, and it’s possible he wouldn’t use any of them.

But many leading experts fear the worst. And if all of this sounds frightening, it should. A new war on the Korean Peninsula wouldn’t be as bad as you think. It would be much, much worse.

Destroying Kim’s nuclear arsenal would require a ground invasion and facing Kim’s chemical and biological weapons

The official position of the Trump administration, like that of its predecessors, is that North Korea’s nuclear program is unacceptable and that Pyongyang has to give up all its nuclear weapons. If the US and South Korea went to war with the North, their key strategic goal would be to capture or destroy all of Pyongyang’s nuclear sites, as well as the bases that house its long-range missiles.

In a startlingly blunt letter to Rep. Ted Lieu (D-CA) last October, Rear Adm. Michael Dumont, speaking on behalf of the Joint Chiefs of Staff, said the “only way to ‘locate and destroy — with complete certainty — all components of North Korea’s nuclear weapons programs’ is through a ground invasion.”

Danush Parvaneh/Vox; AP Images

Estimates of the exact numbers of US troops that would take part in a push north vary widely, but current and former military planners uniformly believe it would require vastly more forces than took part in the invasions of Iraq or Afghanistan.

A South Korean military white paper from 2016, for instance, said the US would need to deploy 690,000 ground troops to South Korea if war broke out. Bruce Bennett, a senior researcher at the RAND Corporation who has spent decades studying North Korea generally and the Kim family specifically, believes those numbers are on the high side, but he thinks the US would need to send at least 200,000 troops into North Korea. By way of comparison, that would be significantly more troops than the US had in either Iraq or Afghanistan at the peaks of those two long wars.

The 2016 assessment says the Pentagon would also need to send 2,000 warplanes and other aircraft to South Korea. The US hasn’t had that much airpower deployed to a single conflict since Vietnam.

The experts I spoke to believe Kim and his generals know that US ground forces are better trained and equipped than North Korean troops, and that North Korea’s aging fleet of 1,300 Soviet-era warplanes is no match for Washington’s state-of-the-art stealth fighters and other jets. So what would happen if US and South Korean troops started pouring into North Korea while American planes launched wave after wave of airstrikes?

The consensus view is that Kim would try to level the playing field by using his vast arsenal of chemical weapons, which is believed to be the biggest and most technologically advanced in the world. (Kim is estimated to have between 2,500 and 5,000 metric tons of deadly nerve agents like sarin, which can cause paralysis and, ultimately, death.)

With so many artillery pieces and rocket launchers trained on Seoul, Kim has the ability to quickly blanket the densely packed city with huge amounts of nerve agents. The human toll would be staggeringly high: The military historian Reid Kirby estimated last June that a sustained sarin attack could kill up to 2.5 million people in Seoul alone, while injuring nearly 7 million more. Men, women, and children would very literally choke to death in the streets of one of the world’s wealthiest and most vibrant cities. It would be mass murder on a scale rarely seen in human history.

Kim also has large quantities of VX, an even deadlier chemical weapon, and has already shown a willingness, and ability, to use it against civilian targets abroad. Last February, two women trained by North Korean intelligence agents walked up to Kim’s estranged half-brother Kim Jong Nam, while the 45-year-old walked through an airport in Malaysia, and smeared his face with VX. Authorities there said he suffered a “very painful” death from his exposure to the nerve agent.

Retired Lt. Gen. Chip Gregson, the Pentagon’s top Asia official from 2009 to 2011, says the attack was a vivid illustration of the North Korean chemical weapons program’s technological sophistication — and of what may face US and South Korean troops if war were to break out.

“VX is the worst of the worst,” Gregson told me. “It’s a crowd killer. It’s odorless, colorless, and doesn’t dissipate quickly. The fact that they were able to use it so precisely — to kill only one person and not even injure the two handlers — indicates a high degree of technical skill and a clear willingness to use a weapon of mass destruction against civilian targets. That needs to be factored into the equation when we think about what Kim would do to preempt an attack or retaliate for one.”

The Pentagon already assumes that its airbases in and around South Korea would be among the first places Kim tried to hit with chemical weapons like sarin. US military officials don’t think North Korea would necessarily succeed in killing many of the pilots and other troops stationed there, all of whom are equipped with gas masks and other protective gear. But they worry an attack could nevertheless make it significantly harder for the US to launch air raids against the North by causing panic and chaos on the bases that house the American warplanes, bombers, and troops.

Retired Air Force Lt. Gen. Jan-Marc Jouas, the former deputy commander of US forces in South Korea, said the initial phases of any offensive against North Korea depend on American and South Korean planes being able to hit Kim’s nuclear facilities, military bases, chemical and biological weapons caches, radar systems, and missile defense arrays.

The air campaign — which would dwarf the “shock and awe” of the Iraq War in size and scope — would be designed to decimate North Korea’s ground forces and destroy the thousands of artillery pieces trained on the South Korean capital before they could be used to level Seoul.

Washington would also try to kill senior North Korean military commanders and government officials, including Kim. (So-called “decapitation” strikes are part of the current US and South Korean war plan for a conflict with North Korea, OPLAN 5015, which explicitly talks about targeting the country’s top leadership.)

“Air power is dependent on the number of sorties that can be flown,” Jouas told me, using the military’s term for an individual air combat mission. “And it’s a lot harder to generate sorties if your airfield is under attack.”

Jouas said Air Force personnel conduct chemical weapons drills where they practice doing their jobs in gas masks and other equipment they’d wear if the bases were under actual attack. They try to game out all the various ways North Korea could hit the facilities, and to prepare accordingly. It isn’t easy.

“We anticipate conventional attacks, we anticipate chemical attacks, we anticipate cyberattacks, and we anticipate North Korean special operations forces being inserted into the bases,” he told me. “We’d still be able to fly — and to ultimately defeat North Korea — but there would be an unquestionable impact on our operations.”

Gregson thinks Kim wouldn’t only use his chemical weapons against military targets in South Korea. The Pentagon has a sizable military presence in neighboring Japan, and the island of Guam is a US territory that is home to more than 163,000 American citizens. Both are well within range of Kim’s missiles and rockets — and Gregson expects both would be hit.

Andrew Weber, formerly the assistant secretary of defense for nuclear, chemical, and biological defense programs, told me that the US and South Korea would also need to be prepared for Kim to use biological weapons against both military and civilian targets.

North Korea’s arsenal is thought to include smallpox, yellow fever, anthrax, hemorrhagic fever, and even plague. They are some of the most frightening substances on earth, and Weber expects some of them to be used against South Korean ports, airfields, and cities as a way of killing large numbers of civilians and troops while causing terror on a nationwide scale.

“We would expect to see cocktails of fast-acting biological agents designed to stop troops in their tracks and regular infectious agents that would take more time to kill people,” he told me. “There would be a significant military impact, and a significant psychological one. It’s hard to overstate just how frightening these types of weapons are.”

In an October 2017 report, researchers from Harvard’s Belfer Center noted that minute quantities of anthrax “equivalent to a few bottles of wine” could kill up to half the population of a densely populated city like Seoul. North Korea could theoretically fire missiles with payloads of anthrax or other biological weapons into South Korea, or use drones to disperse the lethal substances from the air.

The researchers wrote that Kim could also have some of his citizens secretly bring the weapons into the South:

North Korea has 200,000 special forces; even a handful of those special forces armed with BW would be enough to devastate South Korea. What is alarming about human vectors is that they do not need sophisticated training or technology to spread BW amongst the targets, and they are difficult to detect in advance of an attack. It is theoretically possible that North Korean sleeper agents disguised as cleaning and disinfection personnel could disperse BW agents with backpack sprayers. Another possibility is that North Korean agents will introduce BW into water supplies for major metropolitan areas.

In 2011, Weber helped design a war game centered on a simulated North Korean biological weapons attack on the South. The exercise, Able Response, brought together hundreds of military and civilian officials from the US and South Korea. The goals were to figure out the best ways to detect an attack, identify what substance had been used, limit the spread of the virus, and then rush vaccines and other medical care to the infected to save as many lives as possible.

The exercises led to concrete policy changes, including closer coordination between the South Korean military and the country’s public health system. US bases in South Korea received new environmental surveillance systems designed to quickly detect the presence of a biological agent. All US troops in South Korea are vaccinated against anthrax and smallpox (South Korean troops aren’t, to the consternation of Weber and other US officials).

Still, Weber said his main takeaway was the near impossibility of preventing biological weapons from killing an astonishing number of people. The death toll in each year’s exercise was often close to a million. In some cases, it was significantly higher because the infection spread to Japan or other nearby countries.

“It only takes one or two people to deliver bioweapons, and tiny quantities of a bacteria or virus can cause a massive number of casualties,” he told me. “You wouldn’t need a missile. You’d need a backpack.”

The scary logic behind a North Korean nuclear attack

There’s a giant question that looms over any discussion of North Korea’s growing arsenal of nuclear weapons: Would Kim actually be willing to use one?

North Korea is thought to have about 50 nukes. The US, by contrast, has an astonishing 6,800 nuclear weapons (surpassed only by Russia, which has an estimated 7,000 weapons). Trump — or one of his successors — could respond to a North Korean nuclear strike by destroying every major North Korean city in a matter of hours.

Those assessments have now changed. Most of the experts I spoke to believe North Korea would use nuclear weapons at the beginning of a war — not at the end. And most of them believe Kim would be making a rational decision, not a crazy or suicidal one, if he gave the launch order.

One of the best explanations for why came from Bennett, the RAND researcher. He’s mademore than 100 trips to the Korean Peninsula and interviewed an array of North Korean defectors. He also jokes that he’s “kinda, sorta” made it into North Korea itself, including once walking through a newly discovered tunnel that North Korean troops had dug beneath the Demilitarized Zone that separates North and South Korea. He remembers that the walls were covered with graffiti praising Kim.

Bennett began his career at RAND during the height of the Cold War and believes it’s impossible to understand why Kim would go nuclear without also understanding why Soviet leaders were prepared to do so.

“In the Cold War, we specifically talked about a logic called ‘use them or lose them,’ which referred to the fact that the Soviet Union understood that the first goal of an American preemptive attack would be to knock out their nuclear weapons before they could be fired at the US,” Bennett told me. “Now think about how Kim is looking at the world. He knows that any US and South Korean strike would be designed to destroy or capture his nuclear weapons. That means he’d need to either use them early or risk losing them altogether.”

There’s another big-picture reason Kim might decide to go nuclear: a Cold War-era concept known as “decoupling.”

In the 1950s, the Soviet Union was much stronger militarily than Germany, France, or the other countries of Western Europe. The US had formally committed to protecting those nations from a Soviet invasion, and Bennett told me that American military planners were prepared to use small-scale tactical nuclear weapons against the advancing Russian troops to stop the assault.

That entire calculus began to change once the Soviet Union developed long-range nuclear missiles capable of reaching the continental US. European leaders openly wondered how far Washington would be willing to go to protect their countries from the Soviet Union given the new risks to the American homeland.

“By the time you get to the late ’50s, the French in particular are saying, ‘Wait a minute, if the US uses nuclear weapons against Soviet ground forces in Europe, the Soviets are going to fire nuclear weapons at the US. Is the US prepared to trade New York City for Paris?’” Bennett told me.

That’s why North Korea’s new generation of long-range missiles capable of hitting the mainland US is such a game changer.

So if Kim actually wants to try to reunify the two Koreas, he needs to somehow break up the US-South Korea alliance. If the US were no longer willing to defend Seoul, then South Korea — which has no nuclear weapons of its own — would be a lot easier to invade and defeat. But how do you break up that alliance? How do you convince the US not to come to South Korea’s defense in case of war?

Being able to credibly threaten to destroy New York or Washington definitely helps. Kim can now force American leaders to stop and think whether it’s really worth risking a possible nuclear attack on the US mainland just to defend South Korea from a North Korean attack. North Korea has missiles capable of reaching the West Coast and is thought to have nuclear warheads that would fit on top of them. They could destroy a major nuclear city. To modify a phrase from the Cold War, would Trump be prepared to trade San Francisco for Seoul?

If Kim decides the answer is no, using a nuclear weapon against South Korea no longer seems crazy or suicidal. It starts to seem rational. And one particular South Korean city starts to seem like the likeliest target.

In July 2016, Kim test-fired three missiles as part of what a North Korean state-run news agency described as mock “pre-emptive strikes at ports and airfields in the operational theater in South Korea, where the U.S. imperialists nuclear war hardware is to be hurled” in case of a future conflict between the two sides.

That was widely seen as an implicit threat to use nuclear weapons against the South Korean port city of Busan, which would play a vital role in any Pentagon effort to build a force big enough to defend the South or to lead a preemptive strike on the North.

The US currently has around 28,500 troops stationed in South Korea and would need to deploy hundreds of thousands more if war broke out with the North. The US would also have to send in thousands of additional tanks, armored personnel carriers, bombers, fighter jets, helicopters, and artillery pieces.

The problem is that the Pentagon’s cargo planes can only ferry in a few hundred troops or a couple of tanks at a time. That means the vast bulk of the US troops and equipment would need to come by boat, a laborious process that could take six weeks or longer to complete. The American ships would unload at Busan, and the best way for Kim to destroy those ports — and significantly slow US efforts to send in enough troops to make a difference in the fight — would be to nuke the city.

Jouas, the retired Air Force general, told me that North Korea’s thinking about whether to use a nuclear weapon early in a conflict has likely changed as the country has built more of the weapons and developed missiles and rockets capable of hitting more distant targets.

“In the past, when North Korea had a limited number of nuclear weapons, the assessment was that they’d marshal them to use only as a last resort,” he told me. “Now that their inventory has grown, it’s easier to imagine them using some of the weapons at the onset of hostilities to try to shape the way the rest of the war would unfold.”

Bruce Klingner, a 20-year veteran of the CIA who spent years studying North Korea, told me that Iraqi leader Saddam Hussein had stood by in 2002 as the US methodically built up the forces it used to invade the country — and oust Hussein — the following year. He said there was little chance that Kim would follow in Hussein’s footsteps and patiently allow the Pentagon to deploy the troops and equipment it would need for a full-on war with North Korea.

“The conventional wisdom used to be that North Korea would use only nuclear weapons as part of a last gasp, twilight of the gods, pull the temple down upon themselves kind of move,” said Klingner, who now works for the conservative Heritage Foundation. “But we have to prepare for the real possibility that Kim would use nuclear weapons in the early stages of a conflict, not the latter ones.”

We also have to prepare for the fact that if the US and North Korea do actually come to blows, China will get involved — and not in the ways that either Washington or Pyongyang might expect.

The China problem

In a recent essay in Foreign Affairs, Oriana Skylar Mastro, a North Korea expert at Georgetown University, argues persuasively that the US fundamentally misunderstands China’s relationship with the Kim government. US officials have long believed that Beijing is committed to North Korea’s survival and might take steps to ensure that Kim’s regime doesn’t collapse and send millions of starving refugees flowing into China. That line of thinking, she writes, is “dangerously out of date.”

Mastro continues:

Today, China is no longer wedded to North Korea’s survival. In the event of a conflict or the regime’s collapse, Chinese forces would intervene to a degree not previously expected — not to protect Beijing’s supposed ally but to secure its own interests.

More specifically, she and several of the other experts I spoke to believe that China would quickly send hundreds of thousands of troops into North Korea to seize control of the country’s nuclear sites and prevent Kim from using the weapons. Chinese and North Korean troops wouldn’t be working together against a common enemy; they’d be trying to kill each other.

“China would have to fight its way into North Korea,” Mastro told me in an interview. “For the North Koreans, enemy No. 1 is obviously the United States, but enemy No. 2 is China. They understand they’d have to potentially fight both countries.”

Things would get really complicated, and really dangerous, once Chinese troops made their way to the nuclear facilities. The Pentagon has spent years practicing how to send US special operations forces into North Korea to seize Pyongyang’s nuclear weapons if there were signs that Kim’s government was collapsing. The problem is that Chinese troops would almost certainly be sent into North Korea at the same time, and with the same goal, as the US forces.

Mastro notes that Chinese troops would only need to advance 60 miles into North Korea to take control of all of the country’s highest-priority nuclear sites and two-thirds of its highest-priority missile sites. Given that enormous geographic advantage, Beijing’s troops would almost certainly arrive before the US ones do.

There’s no reason to think the countries would necessarily come to blows. The US could live with the North Korean nuclear weapons ending up in China’s hands, since Beijing already has a sizable nuclear arsenal and relatively stable relationships with both Washington and many of its neighbors in the region.

But Beijing would be intervening to protect its own interests, not those of the US. A war between North and South Korea would almost certainly end with the creation of a reunified country led by the pro-US government in Seoul; China would want to make sure it wasn’t left out in the cold.

In this, and this alone, a war with North Korea would bear some similarities to the war in Iraq. When the Bush administration ousted the Saddam Hussein regime in 2003, it wasn’t prepared for what became a concerted and years-long Iranian push to ensure that Iraq’s political system was dominated by Shia political parties with close ties to Tehran. Iran has largely gotten its way: Several of Iraq’s postwar leaders have allowed Iranian militias to operate within the country, and Baghdad has noticeably chilly relationships with Saudi Arabia and Iran’s other regional rivals.

All of which is to say that China, like Iran, would be trying to stabilize postwar Korea on its own terms, not those of the US. And it would be doing so against a Trump administration that is notably hostile and fearful of China’s rising global influence.

Trump and Kim have the ability to start a nuclear war. Will they walk back from the brink?

So how scared should we be?

That, more than anything else, is the question that’s been on my mind for the weeks I’ve spent reporting this story. The good news is that the experts I spoke to don’t think war is inevitable, or even probable. Most, like Jung Pak, a former North Korea analyst for the CIA, believe that Kim is a rational leader who has been careful during his years in power to walk right up to the edge without going over it.

“People say he’s young and untested, but he’s not that young anymore and he’s not that untested anymore,” she said, noting that Kim has led his country since 2011 and has managed to massively expand his nuclear arsenal without triggering a war with the US or South Korea. “He’s a brutal dictator that is aggressive and vindictive and prone to violence, but he’s a rational leader making fundamentally rational choices. He knows how to dial things up, but he also knows how to recalibrate and dial them back down.”

Pak and others note there have been some recent, fragile signs of diplomatic progress. North and South Korea just announced plans for their athletes to train together in advance of the Winter Olympics and enter the opening ceremonies as one team, under the flag of a reunified Korea. The North and South Korean governments are holding ongoing talks, and South Korea and the US agreed to postpone new military exercises until after the Olympics, a move widely seen as a goodwill gesture to North Korea. Trump is for the moment saying he’scommitted to diplomacy and believes he would “probably have a very good relationship with Kim Jong Un.”

But here’s the bad news, and the reason hours of conversations with some of the people who know North Korea best have left me feeling profoundly unsettled: It’s easy to imagine a misunderstanding or accidental run-in between the two skittish countries leading to a full-blown war.

“I have queasy feeling that we’re in 1914 stumbling towards Sarajevo,” Sen. Angus King (I-ME)said during a Senate Armed Services Committee hearing last September, a reference to the assassination of an Austrian archduke that triggered the devastation of World War I. “And what worries me is not an instantaneous nuclear confrontation, but an accidental escalation based upon the rhetoric that’s going back and forth.”

King continued:

That’s what worries me, is a misinterpretation, a misunderstanding, an event: a shooting down of a bomber, a strike on a ship that leads to a countermeasure, that leads to a countermeasure, and the end result is that if Kim Jong Un feels his regime is under attack, then the unthinkable happens.

He then asked Joint Chiefs of Staff Chairman Gen. Joseph Dunford, who was testifying at the session, if the US and North Korea had any direct lines of communication that could be used to defuse a tense situation before it spirals out of control.

“We do not,” Dunford replied.

And that’s the most dangerous aspect of the current standoff, and the issue that could most easily lead to a conflict whose potential human costs are so high — millions dead, millions more wounded, major cities lying in ruins — as to be almost unimaginable.

The US is led by a hotheaded president who lacks military experience, is prone to unpredictable flashes of rage and fury, talks openly of destroying another sovereign country, and has alarmed advisers with his ignorance about America’s massive number of nuclear weapons and seemingly blasé attitude toward their use. (Secretary of State Rex Tillerson’s comment that Trump was a “****ing moron” came after the president told his top advisers that he wanted a tenfold increase in the size of the US nuclear arsenal.)

North Korea is led by Kim, a man who rarely leaves his own country, has executed scores of relatives and high-ranking officials, literally starves his own people to free up money for his country’s nuclear program, and regularly uses apocalyptic language to describe what he sees as a coming war with the US and South Korea.

Maybe next week Kim will test-fire a missile that flies too close to Guam or Hawaii and Trump will decide enough is enough. Or maybe a US ship will accidentally drift into North Korean waters and Kim’s navy will open fire. With no lines of communication, a simple mistake could set off a cascading series of responses that ultimately lead to all-out war. In a situation this combustible, there are an enormous number of moves — some intentional, some accidental — that could light the match.

CREDITS
Editors: Ezra Klein and Jennifer Williams
Graphics: Javier Zarracina
Art direction: Kainaz Amaria
Video: Danush Parvaneh
Video art direction: Alex Cannon
Video producer: A.J. Chavar
Video colorist: Carlos Waters
Audio engineer: Peter Leonard
Copy editor: Tanya Pai