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In this moment of heated, belligerent rhetoric about a military confrontation with North Korea, 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.

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

Former Defense Secretary Robert 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.

“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 trying to lure the Kim regime to the table, a military confrontation remains a “plausible path,” Nephew said.

The spate of North Korean agitation is hardly new. Security experts in Washington debated 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 it exploded its first nuclear device in 2006.

A military confrontation could start with a U.S. effort to force regime change. “But it’s hard to imagine that scenario ending with anything other than the North Koreans deciding to light up Seoul,” Nephew said.

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 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.

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.

Skirmishes have taken place at the border 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. 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 a near-total collapse of civil order.

“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,” said Thomas Mahnken, president of the Center for Strategic and Budgetary Assessments, which does war-game planning.