By Henry Farrell, WashingtonPost

President Trump has just taken a break from his 17-day vacation to threaten North Korea. His words:

North Korea best not make any more threats to the United States. They will be met with fire and fury like the world has never seen. He has been very threatening beyond a normal state. And as I said, they will be met with fire, fury and frankly power, the likes of which this world has never seen before.

This threat is a response to a continuing series of provocations by North Korea. The problem is that threats have consequences for credibility. U.S. leaders have traditionally been careful with their language, especially when dealing with nuclear powers, and for good reason. Trump’s threat is more likely to lead to dangerous escalation than to make North Korea back down.

Escalation can be a very bad thing

Nuclear weapons are the most devastating kinetic weapons known to man. While fears of a mutual conflagration that would destroy human life on this planet have diminished, even a limited nuclear war could cause millions of human deaths.

Fears of all-out nuclear war dominated the historical relationship between the United States and the Soviet Union. Both sides faced the temptation of brinkmanship — pushing to the very edge of open hostility to extract concessions from the other.

But brinkmanship is a dangerous game. If you miscalculate your threats or misunderstand the other side’s motivations, you might leave the other side with no choice but to respond aggressively. This might lead to a war of mutually assured destruction that neither side wants but neither side can avoid.

The Cuban missile crisis was a classic example of brinkmanship, in which mutually escalating threats between the United States and the Soviet Union nearly led to war. Had things gone a little differently, the world might have seen a devastating nuclear conflict. The near miss helped provoke serious rethinking on both sides about how they could manage their many conflicts of interest without outright war.

Nuclear weapons led to concerns about credibility and deterrence

After the crisis, U.S. (and eventually U.S.S.R.) strategic thinkers, such as Nobel Prize-winning economist Thomas Schelling, started to radically rethink the politics of conflict. The U.S. and Soviet Union were deeply hostile to each other — but neither wanted a war, and both wanted to avoid the mistakes that might accidentally precipitate one. This is what produced the Cold War, a kind of shadow conflict in which the two countries jockeyed for advantage through proxy conflicts and other means, without ever engaging in direct and open conflict.

The Cold War happened in the shadow of the hot war involving nuclear weapons that was never actually fought. Each side looked to use implicit or explicit threats to deter the other from doing things it didn’t want it to do, outlining the consequences if their adversaries went ahead.

To be effective, such threats had to be credible. The other side had to believe that the threat would be delivered on, even if it had painful consequences for the threatening party. This meant that leaders — even when they were vociferous in other ways — were extremely careful about even implicit threats of military action against another nuclear power. They feared that if their bluff was called, they would either have to deliver on the threat, or face the risk that their adversaries would not believe in their threats in future, greatly damaging their ability to influence their adversaries’ actions.

This is the dilemma that Trump has created

Trump has now threatened “fire and fury” and “power” against North Korea in a classic example of brinkmanship. Trump is not noted for clarity of language, or for command of the subtleties of international politics, and the threat is rather fuzzily worded. Still, its plain-language meaning would suggest that Trump is telling North Korea that if it issues any further threats of any sort to the United States, it will suffer dire military consequences.

It is possible that North Korea will believe Trump and soften its rhetoric. But it may very plausibly decide that Trump’s threat is unbelievable.

First, a threat of massive military retaliation might seem a disproportionate response to political rhetoric, however threatening. After all, the United States has tolerated — and mostly ignored — bellicose rhetoric from North Korea for decades.

Second, if the United States decides to go to war against North Korea, the country can retaliate. At a minimum, it can use conventional artillery to devastate Seoul and much of the rest of South Korea, which is an important political ally, and it can always threaten to escalate to nuclear warheads.

Third, North Korea may believe that it can count on the support of China — which is a genuinely formidable power — in a military crisis. Finally, while North Korea has few friends, Trump is a weak U.S. leader who may have difficulty in getting support from key allies.

So what happens if North Korea continues its behavior? It will be highly costly, and possibly greatly damaging to the United States to deliver on Trump’s threat, even in its minimal form. If the threat leads to further brinkmanship and an out-and-out nuclear war, it will obviously be far worse still.

Yet if Trump, as is more likely, fails to deliver on the threat, then Trump’s credibility, such as it is, will be badly damaged, as might the credibility of the United States in future standoffs. In particular, it will be even harder to influence North Korea’s behavior.

International relations scholars disagree about the extent to which credibility carries across time, issue areas and relationships with different states. Perhaps other states will see the Trump administration, which has behaved in unprecedented ways, as a temporary aberration, and not draw any long-term conclusions about U.S. strength and willingness to live up to its commitments. Or perhaps not.