In the “fire and fury” phase of Trump’s presidency everyone worried that he’d impulsively start a war with North Korea.

The worry should have been he’d, almost on a whim, step across the Korean DMZ in a chummy photo-op with Kim Jong Un.

Richard Nixon famously had his ”madman” theory of bringing our adversaries to heel by impressing on them his bellicose unpredictability. They’d better talk, otherwise the crazed anti-communist Nixon might nuke somebody.

It’s easy to see the inherent appeal of this theory to Trump, who has cited it in congratulating himself for avoiding war with North Korea. But the president, despite the occasional over-the-top threat, is not a natural madman in this Nixonian sense. He’s not a mad bomber; he’s the mad negotiator.

Does a South Korean delegation have an offer from Kim Jong Un to negotiate directly, with little or no preparation and fuzzy goals? By all means, let’s accept it, and make the meeting a captivating show.

Is US envoy Zalmay Khalilzad nearing a deal with the Taliban? Let’s get leaders of the insurgency to the storied retreat of US presidents, Camp David. Will Trump and Iranian president Hassan Rouhani both be at the upcoming UN General Assembly meeting? Let’s talk.

Trump has taken the old Obama statement from a 2008 debate that he’d be willing to meet without precondition with the leaders of rogue states, and made it an animating principle of his foreign policy.

This is why the Russian conspiracy theorists have always been off the mark. They’ve long believed — and still can’t shake the sense — that Putin “must have something” on Trump to account for the president’s eagerness to come to some sort of unspecified arrangement with him. By this reasoning the Taliban, Kim, Chinese President Xi Jinping and Rouhani all must have something on Trump, too.

Trump sees the best in even the world’s most dismal actors because he sees them, no matter how hostile or blood-stained, as potential negotiating partners. Indeed, the more hostile and blood-stained they are, the more alluring they appear — because any deal would be ever more epic and validating of Trump’s image as the ultimate deal-maker.

Trump is often interpreted in Jacksonian terms, and rightly so. And yet he goes well beyond a traditional Jacksonian’s instinct to leave the world alone until, when a threat emerges, he feels compelled to pound it into sand.

He’s a Jacksonian as real estate developer; he doesn’t want to leave the world alone — or pound it into sand — so much as have attention-getting ribbon-cutting ceremonies after audacious deals that prove the doubters wrong.

The M.O. of a publicity-conscious real estate guy is, once you’ve cut the deal, even if it isn’t really the best one ever, you insist it is. Your building is almost sold out, rich and famous people are buying there, the prices are above market rates, etc. This is what is known as puffery, and Kim Jong Un has been the beneficiary of it.

Even though Kim’s missile program continues apace and the prospect of him denuclearizing is as distant as ever, Trump still insists that they are great friends.

There are, to be sure, things to be said for Trump’s dealmaking-first approach. When it comes to China, for example, there is at least a colorable case for making a trade deal the priority over anything else right now.

Thanks to his flair for the dramatic and his belief in walking away from the table as a tactic, Trump has been willing to blow up his most dubious diplomatic gambits — namely, the deal that was in the offing during the Kim summit in Vietnam and the proposed Taliban visit to Camp David.

From one point of view, Trump is an exaggerated version of the mistake many US presidents tend to make. Because getting elected president means by definition that they have better-than-average persuasive skills, presidents often have an outsized view of their own ability to personally sway other leaders.

Obviously, Trump takes it to another level. The problem with his worldview is that, counter to its supposed hard-bitten realism, it depends on the idea that ultimately, yes, we can all get along, assuming the right dealmaker is in the Oval Office.

But no tool of foreign policy, including diplomacy, should be deployed indiscriminately and thoughtlessly. Some hands aren’t worth shaking, some ribbons not worth cutting.