A military confrontation with North Korea may now be “inevitable,” says Sen. Lindsey O. Graham (R-S.C.) The United States is “done talking” about North Korea, tweets U.N. Ambassador Nikki Haley. President Trump threatens “fire and fury like the world has never seen,” then says maybe his language “wasn’t tough enough.”

The North Koreans return verbal fire, talking of using “absolute force” to hit the U.S. territory of Guam and even “turn the U.S. mainland into the theater of a nuclear war.”

In this moment of heated, belligerent rhetoric, planners in and out of government are diving into decades of plans and projections, playing out war games, engaging in the macabre semi-science of estimating death tolls and predicting how an adversary might behave. Inside Washington’s “what if?” industry, people at think tanks, universities, consultancies and defense businesses have spent four decades playing out scenarios that the Trump administration now faces anew.

The pathways that have been examined fall into four main categories: doing nothing, hitting Kim Jong Un’s regime with tougher sanctions, pushing for talks, and military confrontation. An armed conflict could take place in disparate spots thousands of miles apart, involving any number of nations and a wide variety of weapons, conventional or nuclear.

In hundreds of books, policy papers and roundtable discussions, experts have couched various shades of armageddon in the dry, emotion-stripped language of throw-weights and missile ranges. But the nightmare scenarios are simple enough: In a launch from North Korea, a nuclear-tipped missile could reach San Francisco in half an hour. A nuclear attack on Seoul, South Korea’s capital of 10 million people, could start and finish in three minutes.

View Graphic North Korea has launched 18 missile tests in 2017, and 13 were successful.

Talking tough about war doesn’t necessarily lead to it. Inflammatory language can work both ways, sometimes lighting the fuse of battle, sometimes bringing the parties to an easing of tensions.

At this volatile intersection, alternatives to war are at least as much the focus as preparation for battle. Luring the North Koreans to the negotiating table is perhaps the most popular pathway among many experts, who advocate a “freeze-for-freeze” option, in which the United States might promise to restrict military exercises in the region or eschew new sanctions against Kim’s regime, in exchange for North Korea agreeing to halt expansion and testing of its nuclear capabilities.

Former defense secretary Robert M. Gates, for example, has suggested promising not to seek regime change in North Korea in exchange for Kim committing to a cap on his nuclear program.

However, Susan Thornton, the acting assistant secretary of state for East Asian and Pacific affairs, said the Trump administration rejects the idea of freeze-for-freeze, calling it a false moral equivalency.

Accepting North Korea into the world’s nuclear club is a hard step for many politicians, but maybe not quite as hard as it once was. Now, it’s not so much a step as an acceptance of the status quo.

“I don’t think we’re going to get denuclearization,” said Richard Nephew, a scholar at Columbia University who was a sanctions coordinator in President Barack Obama’s State Department. “So we might want to accept them and depend on deterrence theory. There’s a reason North Korea has not invaded South Korea: They fear overwhelming response from the United States.”

But if North Korea won’t negotiate, or if the Trump administration decides against making concessions that might lure the Kim regime to the table, a military confrontation remains “a very plausible path,” Nephew said. “It’s a very tempting idea to solve this problem once and for all.”

(Anna Fifield,Jason Aldag/The Washington Post)

The current spate of North Korean agitation is hardly a new phenomenon. Security experts in Washington have been debating how best to respond to a nuclear threat from the Kim regime for four decades and three generations of the family’s rule. North Korea was presumed to have nuclear warheads in the 1990s, and the country exploded its first nuclear device in 2006.

A military confrontation could start with a U.S. effort to force regime change, either by taking out the Kim regime or by fomenting a rebellion among elites in the isolated dictatorship.

“But it’s hard to imagine that scenario ending with anything other than the North Koreans deciding to light up Seoul,” Nephew said. And if South Korea were given a voice in any U.S. decision to use force, it’s unlikely that Seoul would assent to a strategy that could spark a wider conflagration on the Korean Peninsula.

Most of those who have considered the merits of launching a limited attack on the North — say, to destroy nuclear capabilities — have concluded that what Americans might see as limited could well be interpreted by the Kim regime as an invitation to all-out conflict.

North Korea might even respond with force to the ongoing U.S. show of strength in its neighborhood. American ships, planes and troops have been on maneuvers nearby as part of annual exercises, and the United States sent B-1 bombers stationed in Guam over the Korean Peninsula last month.

The North could also launch its own provocation — an attack on Guam, a cyberattack on Japan or a skirmish on the boundary between the two Koreas, the planet’s most heavily armed border.

In 2010, for example, the North sank a South Korean naval vessel, the Cheonan, and a few months later shelled Yeonpyeong Island, a South Korean territory in the Yellow Sea, killing two soldiers. In those cases, “South Korea took hits and did not retaliate,” said Richard Lacquement, a retired Army colonel who served as a military planner in South Korea. But if they did retaliate, he wondered, might that ignite a larger war?

If the latest North Korean threats about hitting Guam reflect any real intent beyond rhetorical saber-rattling, a launch would be detected by Japanese radar, leading U.S. ships in the Pacific to launch missiles to destroy the North Korean warhead, according to one scenario. The immediate crisis might be averted, but North Korea might then respond by attacking South Korean patrol boats near the border between the two Koreas.

Skirmishes have taken place in that area for many years, but the chances that such a conflict could quickly metastasize into a full-scale war are high, military analysts said.

In a conventional war, heavy casualties would likely result as North Korean troops poured into the South, using tunnels the North is reported to have built under the demilitarized zone between the countries. In addition, North Korea is believed to have a stockpile of several thousand tons of chemical weapons, according to the International Crisis Group, which studies global conflicts.

In war games played out at Washington policy institutes, even minor confrontations have led to a nuclear exchange. In one model, a single nuclear device deployed against Seoul would result in 180,000 deaths and 160,000 additional injuries, along with a near-total collapse of civil order, including a mass exodus from the city leading to gridlock and a paralyzed health-care system.

Even without using nuclear weapons, the North could sow panic and perhaps force a shift in U.S. policy. North Korea might attempt to spread fear through an act of terrorism, said Patrick Cronin, an Asia-Pacific security expert at the Center for a New American Security. “A few grenades in downtown Seoul will absolutely close down the city out of fear,” he said.

Even without nuclear force, North Korea might seek to divide the United States from its allies. How, for example, would regional Asian powers react if North Korea shot a high-altitude electromagnetic pulse over Tokyo, temporarily turning off the lights in the Japanese metropolis?

In that instance, some experts concluded, Japan might join with some neighbors to urge Washington to cut a deal with Kim, averting further military conflict by accepting North Korea as a nuclear power.

North Korea has “proven adept over the years at using force in pretty calibrated ways to achieve political objectives,” said Thomas Mahnken, president of the Center for Strategic and Budgetary Assessments, which does war-game planning. He said the North takes advantage of the relative unwillingness of the United States and South Korea to risk war.

“We lived in a period from the end of the Cold War until the recent past where we could delude ourselves that we lived in a risk-free world — and that era is over,” Mahnken said.

Many scenarios exploring how a U.S.-North Korea conflict would unfold founder on uncertainties about what Kim really wants. Despite the country’s acquisition of nuclear weapons, “the regime does not have regional ambitions,” concluded Robert Carlin of Stanford University and Robert Jervis of Columbia in a paper that studied how North Korea might use its new status.

“The most likely scenario,” they wrote, “is for Pyongyang to remain tightly focused on its domestic situation, especially on its economy, and on ways to loosen or blunt the pressures from its neighbors and the United States.”

Still, they said, “we could well enter the danger zone of North Korean fatalism, in which a decision to use nuclear weapons, especially against Japan — the historic enemy — would rise on the list of ‘patriotic’ options.”

The North Korean leadership, they warned, “might become. . . fatalistic and decide that death with ‘glory’ is preferable to defeat.”