President Trump's political rhetoric on North Korea has differed from before he declared his candidacy to now. (Taylor Turner/The Washington Post)

In international security, there is no area where careful signaling is more important than with nuclear weapons. Precisely because nuclear weapons have not been used since 1945 and only would be in the gravest of circumstances, nuclear declaratory policy — the official statements that describe the conditions under which the United States might use nuclear weapons — takes on a special weight.

Presidential and other high-level statements on nuclear policy help to deter adversaries and assure treaty allies of the United States’ commitment to their security. Recently, however, some of the most basic tenets of international nuclear signaling were scorched by President Trump’s threats of “fire and fury” toward North Korea. Here are five lessons from his war of words with Kim Jong Un.

During his stay at his Bedminster, N.J., golf club on Aug. 8, President Trump said North Korea "will be met with fire and fury like the world has never seen" if they continue making nuclear "threats." (Reuters)

1. Trump ignored nuclear policy and strategy

In his “fire and fury” comments, Trump gave a warning to North Korea that had no historical precedent and was a consummate “commitment trap”: a scenario in which a leader stakes his credibility on a promise that leaves him with two bad options. He seemingly threatened a first nuclear strike as the response to any threats from Pyongyang.

From a policy perspective, this was stunning. Even at the height of the Cold War, U.S. leaders did not threaten nuclear use in response to mere threats. From a strategy perspective, Trump’s construct was foolish. It left him with the unhappy choice between backing down when North Korea next provoked or following through and launching a catastrophic conflict.

Secretary of State Rex Tillerson said Americans should have "no concern" about North Korea's threats to the United States on Aug. 9. (The Washington Post)

2. The Trump administration does not have a unitary nuclear declaratory policy

Trump’s secretaries of state and defense attempted to reshape his statements, but the president simply doubled down with another apocalyptic tirade. Four days later, Rex Tillerson and Jim Mattis again offered sound policy in print, but this cycle of presidential bombast and Cabinet mollification carves a credibility chasm. The 2018 U.S. Nuclear Posture Review will presumably not sanction the first use of nuclear weapons in response to mere threats. Still, Trump’s words cannot be dismissed as rhetoric. Going forward, should international parties dismiss the president’s words and trust more measured statements, even though the president has the sole authority to order a nuclear attack?

3. Trump wasn’t just talking to allies and adversaries

We often think of American nuclear signaling as directed toward two primary audiences: the adversary the United States seeks to deter and the allies it seeks to assure. But Trump’s nuclear bombast may have had two other audiences that ranked ahead of these.

The first audience was Trump’s domestic base, his hardcore supporters. Trump’s poll numbers plummeted after the spate of White House firings in late July; “fire and fury” got him an unmistakable bounce. Plenty of international relations research shows how leaders can create “audience costs” by tying their international signals to their domestic political fates.

The trouble is, this mechanism can’t explain Trump’s nuclear pandering. The president’s base may swoon over his unilateral nuclear threats, but the vast majority of the American people find them unnerving.

The second audience was China, which Trump has long believed would “fix” the North Korea problem for the United States. China supports as much as 90 percent of the North Korean economy and is central to any efforts to isolate Pyongyang. Beijing has long prioritized stability over denuclearization on the peninsula. It hesitates to crack down on North Korea, lest the Kim regime stumble. Trump probably hoped his threats would startle Beijing into cracking down on its wayward ward, despite the messages themselves being incredible.


A mushroom cloud balloons after the first test of a hydrogen bomb, “Ivy Mike,” photographed by the Air Force in 1952 on Enewetak, an atoll in the Pacific Ocean. (DSWA-DASIAC via Reuters)

4. Trump played the mad man, while North Korea and China played it cool

One might argue that Trump’s nuclear threats were his version of a “madman” strategy — he cowed his adversaries into submission with punishing words, even though there was little chance he would really act as he says. In response, we would generally expect an adversary to either escalate in brinkmanship or back down.

North Korea and China did neither.

Instead, each responded with tailored signals of their own that advanced their interests. China published an editorial in a state-run newspaper — akin to an official statement — pledging that it would support neither North Korea nor the United States if the former struck first. It sought to induce caution on both sides and reduce its risk of entrapment.

North Korea played its own hand deftly, releasing a detailed conditional plan for a coercive missile display. The plan to fire missiles over Japan toward Guam created a no-win situation for the United States. Should it attempt to use its missile defense to intercept all of North Korea’s missiles, knowing it might miss some — or take no action? Either move would unnerve U.S. allies who count on the American defense umbrella. By suggesting that the plan could be paused, however, Pyongyang invited U.S. engagement to halt it.

Both China’s and North Korea’s responses attempted to de-escalate and recoup leverage. Histrionics were met with rationality, and crazy didn’t win.

5. There may be lasting damage to U.S. alliances in Asia

Trump has not disguised his disdain for America’s alliances and has previously rattled Seoul by maligning important trade and missile defense deals. With his nuclear threats, however, he has done more serious damage to the U.S.-South Korea alliance.

The South Korean public’s confidence in the United States has plummeted under Trump. The country now has a progressive president who wants to engage with Pyongyang. President Moon Jae-in has admonished Trump’s attempts to trap his country in a conflict, declaring that “we cannot rely on our ally for our security.”

Even when this episode passes, the rift will be hard to mend. Moon will be less inclined to coordinate North Korea strategy with the United States. Should the United States attempt to pressure North Korea, Moon could take some of that pressure off by continuing diplomacy despite the U.S. approach. He will be less likely to agree to future missile defense deployments and may be warier of trilateral cooperation with Japan. Right-wing voices in South Korea who favor a domestic nuclear capability may also feel emboldened, and politicians from all political parties may seek a more independent defense policy.

So why did Trump do it?

Trump’s preoccupation with his base and China help explain why he was unconcerned about sending credible threats to North Korea or assurance to the South. But this choice of audience is also a reminder of Trump’s short time horizons: He preferred to score immediate domestic points and give a challenger a fright, even at the cost of his credibility and America’s influence.

A week on the rhetorical brink leads to a final, startling question: When the United States declares its nuclear intentions, who should be believed? The president or his defense team? Allies, adversaries and Trump’s domestic audience have no easy task as they strain to hear the signal in the fire and fury.

Mira Rapp-Hooper is a senior research scholar at the Paul Tsai China Center at Yale Law School and an adjunct senior fellow at the Center for a New American Security.