In this photo provided by the North Korean government, North Korea’s leader Kim Jong Un is said to be inspecting artillery launchers ahead of a military drill marking the 85th anniversary of the establishment of the Korean People’s Army (KPA) on April 25, 2017. (NORTHKOREA-TOURISM/WONSAN KCNA/via REUTERS)

Donald Trump has threatened to “totally destroy” North Korea with “fire and fury” should it cross some ambiguous tripwire. By being vague about where that tripwire lies, Trump seems to believe that his threat, coupled with harsher economic sanctions, will force Kim Jong Un to back down.

But just the opposite seems to have occurred. Instead, a war of words has broken out between Trump and Kim. This underscores the dangers that arise when there are no clear policy guidelines about what conditions constitute a threat to peace and can lead to war. It also tells us what may happen when each leader plays a “madman strategy” — pretending to be a madman to induce his antagonist to capitulate.

Game theorists such as Thomas Schelling have pointed out that the madman strategy can sometimes get results. It is equivalent to throwing the steering wheel out the window of your car, in sight of your adversary, when playing a game of chicken — showing that you are not going to be able to swerve, so your adversary must do so to avoid a head-on collision. Clearly, chicken is a dangerous game.

President Trump harshly criticized North Korean leader Kim Jong Un at the United Nations on Sept. 19, calling him "Rocket Man" and threatening to "totally destroy North Korea" if need be. (The Washington Post)

On the one hand, disaster might strike if both players stick with the madman strategy of making irrevocable commitments. The personal invectives and threats that Trump and Kim have hurled at each other might eventually be sufficient to cause one of them to escalate to nuclear war. If their posturing becomes real, this strategy’s logic leads to mutual catastrophe.

However, each player fears that it may lose — admittedly, in a less costly way than suffering nuclear attack — if it backs down by stepping away from the nuclear brink, thus undermining its future credibility. Each wants to win the confrontation, forcing the other to lose by backing down. This may end with both players refusing to back down and, consequently, crashing.

So what can be done?

One option is to continue more or less as is, posturing in the hope that it will not lead to nuclear war. A second is to be explicit about what tripwire might lead to a nuclear confrontation. A third is to create an externally observable “bright line” to reassure North Korea, and perhaps other adversaries, that there will be no escalation unless something untoward happens.

Clarity may be more helpful than ambiguity

Trump has been relentlessly ambiguous, sometimes inconsistent, about what might lead him to destroy North Korea. Kim has been inconsistent, too. This could create real problems should tensions continue to rise as a result of their blustering. Even before developing nuclear weapons, North Korea was a provocateur in some nasty military incidents with the United States — but none escalated into a major military confrontation.

If North Korea did launch an all-out military offensive, using only conventional weapons, against South Korea and U.S. forces stationed there, the damage inflicted would be horrendous, but relying on U.S. air and naval power would surely enable South Korea to repel such an attack. The problem is that North Korea could unleash its nuclear weapons as a last resort. With that in mind, the United States might preempt this attack by using its own nuclear weapons to limit damage to its own forces.

Alternatively, each side might clarify the conditions that would provoke a nuclear attack, making the tripwire extremely clear. Historically, that approach has undergirded the policy of mutual assured destruction, or MAD, the prevalent nuclear doctrine since the outbreak of the Cold War. Currently, at least one tripwire is clear: The United States has promised massive retaliation should a nuclear attack be detected, even before it hits U.S. territory.

Some analysts claim that MAD prevented nuclear war between the superpowers, although it did not prevent several non-nuclear proxy wars, supported by each side, elsewhere. The fact that none of the seven countries that have acquired nuclear weapons since the 1950s have used them — even between such rivals as India and Pakistan — would seem to validate MAD.

But this is a debatable claim. The world has seen several close calls, involving accidents and last-minute decisions not to launch nuclear weapons. We may just have been lucky so far.

U.S. and South Korea kicked off a week of joint naval drills amid threats from North Korea to fire missiles near Guam. (Reuters)

Verifiable information provides an alternative

An alternative might be for the United States to draw a bright line, requiring verifiable information that a nuclear attack has occurred, before nuclear weapons would be used. Such a policy of No First Use, or NFU, of nuclear weapons has long been advocated by many prominent government officials and foreign policy analysts, both during and after the Cold War.

To be sure, this might undermine U.S. ability to respond to an imminent nuclear attack, including from a major power like Russia. But because it can so powerfully strike back, especially from its relatively invulnerable nuclear-armed submarine force, the United States could credibly promise to retaliate, even against a massive first strike, with devastating force.

What’s more, North Korea is unlikely to be able to hit the continental United States with nuclear weapons. Sure, it might strike vulnerable targets in South Korea, Japan or the Pacific region – but it would do so knowing it could be utterly destroyed in return. Even if North Korea could penetrate U.S. anti-missile defenses, its leaders would have to fear the incalculable damage and destruction from the U.S. response. It is inconceivable that a North Korean sneak nuclear attack could wipe out the U.S. ability to retaliate.

It’s true that a U.S. No First Use policy might send North Korea the wrong signal — letting Kim believe that the U.S. lacks the will to retaliate. Nor would such a policy induce North Korea to relinquish its nuclear weapons, which it claims as a deterrent against a South Korean or U.S. attack on its territory.

On the other hand, a NFU policy might allay North Korea’s fear of imminent attack, reassuring Kim that nuclear attack would come only if he struck first. And it might make both sides less likely to rush hastily into a conventional attack that might escalate into nuclear war.

The logic of NFU has been recognized by three nuclear states: China, India, and Israel. Each has indicated, albeit with some qualifications, that it would not be the first to use nuclear weapons in conflict.

If the United States declared an NFU policy, that might well induce other nuclear states to adopt one as well. Such a domino effect might even persuade North Korea that using nuclear weapons would threaten its very existence. If more and more nuclear states adopted NFU policies, the world might banish the threat of nuclear war, bringing a new global equilibrium.

No First Use won’t prevent all conventional wars between states — but those have become fewer and less destructive over the years anyway. (Destructive civil wars are a different story). But now, for the first time, declaring an NFU policy might deter a small hostile country from using nuclear weapons.

Steven J. Brams is professor of politics at New York University and co-author, with D. Marc Kilgour, of “Game Theory and National Security” (Wiley, 1991).