Tweeting from his golf resort in New Jersey on Sunday morning, the President of the United States disparaged the effort to find a diplomatic solution to the nuclear standoff with North Korea. “I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man,” Donald Trump wrote, using the nickname he has adopted to humiliate the North Korean leader, Kim Jong Un. The President was responding to Tillerson’s recent comment that the U.S. is “probing” for diplomatic solutions via two or three channels to Pyongyang. In his tweets on Sunday, Trump belittled that strategy and suggested that he is more interested in military action: “Save your energy Rex, we’ll do what has to be done!”

You can take the temperature of America’s standoff with North Korea in several ways. Some indicators are reassuring. Were North Korea actually preparing to reduce the United States to “ashes and darkness,” as it recently suggested that it was, American intelligence would be picking up signs of movement—say, ground forces breaking out ammunition, or an uptick in traffic across electronic command-and-control channels. (The U.S. monitors hundreds of such data points every day, down to the location of individual North Korean leaders.) But General Joseph Dunford, the chairman of the Joint Chiefs of Staff, told a Senate committee on Tuesday that the U.S. has detected no “change in the posture of North Korean forces” as a result of the “charged political environment.” Likewise, the U.S. has not moved ground troops or aircraft carriers closer to North Korea. That is no guarantee against a sudden attack—both sides are capable of firing missiles on short notice—but it is a reason not to hyperventilate at every headline.

Beyond the physical indicators, however, the relationship is deteriorating. When I visited North Korea in late August, I left with a sense that, for all the hostility, the confrontation with the United States would lead to talks, not violence. I’m less hopeful of that now, because of President Trump’s seemingly irresistible urge to mock and threaten North Korea’s leader, against the advice of his national-security aides. For months, aides who briefed the President on the conflict had advised him not to personalize the dispute. Unlike in the American arenas where Trump had honed his faith in his instincts—reality television, business deals, political primaries—in North Korea a nickname would not be received as merely a playground jab. At first, Trump complied; in May, he even complimented Kim, calling him a “smart cookie,” and expressed a willingness to meet with him. In Pyongyang, a government official told me that his peers had taken notice of Trump’s tendency to criticize other opponents, but not Kim, a fact that they interpreted as a deliberate effort to maintain the basis for an eventual negotiation.

Then, in mid-September, Trump jumped the guardrails erected by his advisers. He started to mock Kim, calling him Rocket Man, even during a formal address at the United Nations, in front of scores of heads of state—an especially humiliating setting for Kim. In a line that was reportedly added after national-security officials had read the draft, Trump said, “Rocket Man is on a suicide mission for himself and for his regime”; Trump threatened to “totally destroy” North Korea if the United States or its allies were attacked, and in a tweet, a few days later, Trump said North Korea’s leadership may not “be around much longer” if it continues its threats. By extending the taunts to his own Secretary of State, Trump might imagine that he is playing the bad cop to Tillerson’s good cop. At its best, it might be a ham-fisted effort to make Pyongyang more pliable to Tillerson’s entreaties. But this is not a police procedural. In national-security terms, Trump was undermining Tillerson’s credibility in the eyes of his North Korean counterparts. Why should they offer concessions to Tillerson when his boss clearly doesn’t support him?

Trump‘s personalization of the conflict has introduced a new playbook that seems almost perfectly engineered to trigger Kim’s paranoia and animosity. Kim responded to Trump’s U.N. speech by calling him a “mentally deranged U.S. dotard,” a comment that drew laughs here for invoking an obscure term. But, to American specialists on North Korea, it was ominous: Kim’s rhetorical blasts are usually sent out by the state media, but Kim personally delivered this message in a video that was broadcast on North Korean television. It was an unprecedented gesture that has staked his name and his stature on his refusal to back down. More than anything else, Kim’s personal rebuttal signals that the two leaders—each a national-security neophyte navigating his first crisis of this scale—are now locked in a war of egos.

After Trump’s personal taunts of Kim, Evans Revere, a Korea specialist who is a former deputy assistant secretary of state, told me that it is easy for outsiders to underestimate the depth of North Korea’s rage. “I’m a big fan of keeping your adversary off balance, of keeping your adversary guessing about your intentions,” he said. “But this is North Korea, and part of the national credo is the protection of what they call the ‘dignity of their supreme leadership.’ It is so ingrained in their politics, in their society, and their culture.” He added, “At some point, you risk crossing the line, and they just feel compelled to do something. Otherwise, they just end up looking foolish, internally.”

In addition, even by the standards of dictatorships, Kim is acutely sensitive to the risk of looking weak, in part because of his youth. (He is thirty-three.) Not long ago, I met Ri Jong Ho, who was a senior North Korean official until he defected, in 2014. “North Korea is similar to a monarchy of the sixteenth and seventeenth centuries,” Ri told me. In that analogy, Kim is the nervous tyrant. “Although he is worshipped like a god, he does not think that he has stable control over the country. You can see, from his actions, that he is anxious. He’s quick-tempered,” Ri said. “He feels the need to show that he is a bold, daring leader who can make spontaneous decisions, that his power is strong. He is young and proud. He is like a car with no brakes. If his father were alive, he would be controlled, but his father is gone, and there is no one who can control him”

In a dark irony, the lack of controlling influences is one of the features that Kim and Trump have in common. Outside the White House, and around the world, political observers often ask whether the seasoned generals in Trump’s orbit—including H. R. McMaster, the national-security adviser, and James Mattis, the Secretary of Defense—could modulate or interrupt the President’s impulses on complex security questions. Last week, McMaster addressed that question head-on. “There’s nobody there to control the President or ‘keep him on the reservation,’ ” he told a conference at the Institute for the Study of War. “We’re there to serve the President and help him to advance his agenda.”

By personalizing the conflict, Trump has helped to feed a specific strain of North Korean paranoia about efforts to depose—or, in national-security parlance, “decapitate”—the nation’s leadership. In an unusually detailed official statement issued in May, North Korea accused the C.I.A. of a “hideous” plot to assassinate Kim Jong Un, and vowed to “ferret out and butcher every culprit.” South Korean intelligence recently told lawmakers that Kim is increasingly worried about his safety, travelling mostly at night, using decoys and body doubles to disguise his movements. When he leaves his home or Party headquarters, his security guards surround him in at least seven concentric rings, according to research by Ken Gause, at the Center for Naval Analyses, a nonprofit research group in Washington, D.C. When an applicant seeks to work in Kim’s security detail, investigators study the family tree, out to the branches of third cousins, looking for traces of political unreliability.