The regime has never much liked the annual joint U.S.-South Korea military exercises, and has made its feelings known; the exercises have tended to carry on every year without direct consequences to the personnel involved. Nor has the regime ever welcomed American aircraft carriers in its nearby waters or been shy about saying so; those, too, have come and gone unmolested.

What’s different now is Donald Trump. Whereas many of his predecessors steered sedulously clear of escalatory rhetoric, preferring to treat various North Korean leaders as recalcitrant children at worst or distasteful but nevertheless semi-rational negotiating partners at best, Trump has threatened North Korea via Twitter, declaring that the regime is “looking for trouble.” As my colleague Uri Friedman pointed out Thursday, three successive presidents prior to Trump, since the Clinton administration considered military action against the North’s then-nascent nuclear program, have opted for trying negotiations rather than risk a strike. It’s apparent that none succeeded in halting the nuclear program’s progress. But it’s equally apparent that the kind of massive conflagration on the Korean peninsula that world leaders are now warning against has been avoided since 1953.

For allies, enemies, and observers alike, though, Trump appears to be a wild card, and self-avowedly so. Even foreign-policy positions that are “predictable” for an American president—condemning the use of chemical weapons in war, say, or not deriding NATO as obsolete—were unanticipated reversals from this particular president. Trump himself has said that America needs to be more “unpredictable;” as Kevin Sullivan and Karen Tumulty reported in The Washington Post this week, he has made it so, leaving diplomats to ask what exactly the White House intends to do on issues ranging from border-adjustment taxes to Russia. (Russians are themselves confused: A foreign ministry spokeswoman told my colleague Julia Ioffe and other journalists this week: “We don’t understand what they’re going to do in Syria, and not only there. ... No one understands what they’re going to do with Iran, no one understands what they’re going to do with Afghanistan. Excuse me, and I still haven’t said anything about Iraq.”)

On the other hand, where coercive diplomacy is concerned, there are clear advantages to a posture of: “Don’t try it. You have no idea what I’m capable of.” From Cold War deterrence resting on the guarantee of “mutual assured destruction”—you hit me with nukes, I will strike back, even if we incinerate the world—to Barack Obama’s vow to take unspecified measures against Russian hacking “at a time and place of our own choosing,” presidents routinely court risks and instrumentalize uncertainty as a negotiating tactic. If you extract a concession because an enemy fears an attack you had no real intention of carrying out anyway, so much the better. At the very least, there’s the practical advantage that comes with not telegraphing your intentions to an enemy trying to prepare for your next move.