It will be a new sort of special relationship as the men who lead the U.S. and the U.K. work to undo what their predecessors built after World War II.

New British Prime Minister Boris Johnson and U.S. President Donald Trump are political twins of a sortnot identical, but fraternal. They share certain familial traits: funny hair of dubious coloration, an often oafish sense of humor, and a reputation for irremediable mendacity. Above all, Johnson and Trump spring from the same breeding ground of middle-class, anti-globalist rage (politically, that is; personally both men come from wealthy families). They are brothers in demagoguery who have expediently kicked aside old-style conservatism and replaced it with a virulent brand of neonationalism.

And like so many demagogues before them, Trump and Johnson are making reckless promises they cant keep. For Trump, it has been the pretense that a go-it-alone United States freed of international obligations can somehow do better under a new set of unilateralist Trump-branded deals; for Johnson it is that a go-it-alone Britain can accomplish something similar, especially with regard to the European Union. Both men are adept at conjuring the illusion that they can somehow take their countries backward in timeto restore them to their former glory, the theory goeswhile the rest of the world meekly goes along with them.

In fact, the rest of the world is doing nothing of the sort: It has already moved on, forging its own trade deals without the United States and Britain, as my colleague Keith Johnson recently pointed out. But now that Trump and Johnson will be working togetherpossibly in pursuit of dismantling the West as we know ittheres no telling how much damage they could do, if they get enough time.

Whether they will have that time is very much at issue, of course. Trump faces reelection a year from this fall with his approval ratings still well below 50 percent. Johnson, having promised the nation Brexit by Oct. 31 even if theres no deal, is facing the threat of defections from leading Tories who will give him very little time to prove he can do the impossible: renegotiate Theresa Mays failed Brexit deal. (Brussels says flatly that he cant.) His working majority could quickly disappear, especially as polls show Britons are cooling to Brexit and are coming to realize that the ultimate irony of the slogan Johnson and other Leavers deployed during the Brexit campaignTake Back Controlis that Britain has relinquished even more control to Brussels.

In the meantime, however, we will all be witnessing a bizarre backward version of the so-called special relationship, one premised on undoing a great deal of what the U.K. and the United States accomplished together after World War II, when both nations oversaw the creation of postwar institutions such as the United Nations and Bretton Woods; British Foreign Minister Ernest Bevin took the lead in creating NATO (even as an exhausted U.K. bequeathed to the United States the role of stabilizer of the West); and the United States and Britain were the primary progenitors of the global free-trading system.

Now each leader will be swinging his own wrecking ball, said Charles Kupchan, an expert in trans-Atlantic relations at Georgetown University. Kupchan added that even though Trump and Johnson are kindred spirits, I do not expect them to team up on a regular basis. Trump tends not to fashion lasting and meaningful relationships with other world leaders; he prefers to be on his own, putting America first. And Johnson will be so beset handling Brexit that he will have little bandwidth for anything else, including rubbing shoulders with Trump.

That may be true, but theyll be at least winking at each other across the pond. There are major differences, of course, between Johnson and Trump: The new prime minister is intellectually brilliant, erudite, and deeply experienced in politics, while the U.S. president is none of these things. Johnson himself once deplored Trumps treatment of immigrants and called his proposal for a Muslim immigration ban complete and utter nonsense. And after Trump falsely said in 2015 that there were no-go zones in London because of Muslim extremists, then-London Mayor Johnson said Trump had displayed a quite stupefying ignorance that makes him, frankly, unfit to hold the office of president of the United States.

But that hasnt stopped Johnson from sounding even more racist than Trump on occasionhe once dismissed Britains brutal colonial past in Africa by calling the continent a blot and saying, The problem is not that we were once in charge, but that we are not in charge any more. And today, when it comes to broad policy strokes, the two leaders are very much on the same page. Johnson and Trump can also still accomplish much together, especially if the U.S. president deploys his lone-superpower leverage to co-opt the prime minister on issues such as Iranwhich, following the seizure of British-flagged tankers, Johnson may be willing to do. Trump will use his relationship to try to get the U.K. to change its views on the Iran nuclear deal, said Heather Conley of the Center for Strategic and International Studies. Until now, the U.K. has stood with France and Germany in seeking to rescue the 2015 nuclear pact that Trump rejected last year; if it sides with the United States now, that in turn could create more fissures in the trans-Atlantic alliance.

And if Johnson does get his way, he may well end up undoing more than Britains relations with Europe. He could undo the U.K. itself, especially if he succeeds in crashing out of the EU without any deal on tariffs and customs, and if Scotlandwhich wants to stay in the European Uniondecides to re-up a referendum on independence. The spectacle of an incredible shrinking U.K. would only expedite other scary trends, like an inward-looking EU driven by the rise of neonationalists in other European countries following the parliamentary elections in May, and a prolongation of isolationism across the Atlantic.

Trump is plainly eager to have Johnson as an ally in his great task of unmaking the international system. In remarks on Tuesday after Johnson won the Conservative Party vote, the president praised him, somewhat awkwardly, as one of his own ilk. Theyre saying Britain Trump. They call him Britain Trump, and theres people saying thats a good thing, Trump said. They like me over there. Thats what they wanted. Thats what they need.

Johnson, like Trump, is so publicly invested in pushing his all-but-nonexistent agenda forward that hell have little choice but to be all-in. Just as Trump pretended he was giving the American people a better NAFTA deal (which now has little chance of congressional passage) and pulled out of the Trans-Pacific Partnershipwhich had been the single most effective means of forcing China to behave better on trade and intellectual property rightsto show that he could do it better alone (he hasnt), Johnson will take his nation through a similar charade. Egged on by Nigel Farages Brexit Partywhich will threaten him with more Tory defections if he doesnt keep his wordJohnson will continue to pretend to the British people that they can get better trade deals on their own, when most of the evidence is that instead he will bequeath to them international isolation, ever-rising prices, and permanent economic eclipse. And perhaps the eclipse of the Conservative Party as well. The result will be not only a continuing decline of the British economy but also a drag on everyone elses.

This article was published by Foreign Policy on the 24th of July 2019.

Michael Hirsh is a senior correspondent and deputy news editor atForeign Policy.