When the postmortems are written about President Trump’s foreign policy — sooner, we have to hope, rather than later — one phrase will stand out as a hallmark of failure: “maximum pressure.”

Much of this president’s international engagement has been a hodgepodge of impulsive and contradictory actions. But to the extent there is a Trump doctrine, it amounts to this: Use tariffs, sanctions and other means of economic pressure to compel U.S. adversaries — and, as often, allies — to accede to White House demands.

The amount of this pressure has varied from China to South Korea and from Ukraine to Mexico. So have the results. But in three cases — North Korea, Iran and Venezuela — Trump’s explicit policy has been “maximum pressure.” And in those instances, the record at the moment is clear: maximum ­failure.

Maximum pressure was supposed to induce the regime of Kim Jong Un to surrender its entire arsenal of nuclear, chemical and biological weapons. Three years in, it is still building them — and it has now publicly sworn off any further negotiations with the Trump administration. Whether Kim will order a return to the testing of long-range missiles or nuclear warheads in the next few months, thereby provoking an election-year crisis for Trump, remains uncertain. What’s certain is that North Korea will end Trump’s first term with a dozen or so more nukes than it had when he took office.

Maximum pressure was going to force Iran to renegotiate the curbs on its nuclear program — and maybe cause the regime to collapse. Instead, by the end of this year, the regime of Ayatollah Ali Khamenei is likely to have enough enriched uranium to build a bomb, according to the latest Israeli intelligence assessment. The previous deal, which Trump shredded, ensured that Tehran would remain at least a year away.

Iran’s economy has contracted by 10 percent, many of its people are rebellious, and Maj. Gen. Qasem Soleimani, the architect of its foreign adventurism, is dead. But this regime, like Kim’s, has ruled out negotiations with Trump, and so far its willingness to ruthlessly gun down protesters has kept domestic dissent at bay. It, too, could cause Trump trouble between now and November — in this case, with attacks across the Middle East or on the Internet. What won’t happen is a new nuclear deal.

The least noticed but most striking failure of maximum pressure has come in Venezuela, a country just three hours by air from Miami that for decades was deeply dependent on the United States for oil revenue. Trump cut off that income stream, confident it would cause the collapse of a socialist dictatorship already in economic and political free fall.

Instead, a year later, the regime of Nicolás Maduro appears to have stabilized. The lights are back on in Caracas, once-empty stores are full of goods, and the U.S.-backed opposition has been ousted — at least physically — from the National Assembly. Trump’s demand — that Maduro leave office and make way for fresh elections — won’t be realized anytime soon.

So why hasn’t maximum pressure worked? The reasons are not hard to discern. First, Trump set wildly unrealistic goals. As numerous North Korea experts pointed out three years ago, Kim was never going to surrender his entire arsenal at a stroke; at best, he could have been coaxed into a step-by-step process. On Iran, Secretary of State Mike Pompeo demanded a dozen major concessions that were inconceivable without a change of regime. And Venezuela policy supposed that Maduro’s criminal clique, which has nowhere to take refuge, would willingly surrender office — or be overthrown by equally corrupt generals.

Trump’s next mistake was assuming that unilateral U.S. action was enough to succeed, and that he didn’t need the international cooperation obtained by previous presidents. He was wrong. China, whose aid Trump lost when he launched a trade war, has quietly helped North Korea survive sanctions. Russia has done the same for Venezuela, trafficking as much as 70 percent of its oil exports. U.S. allies in Europe have refused to go along with Trump’s voiding of the Iran nuclear deal and reimposition of sanctions. Even Middle East nations such as Saudi Arabia have quietly sought accommodation with Tehran.

Trump’s biggest miscalculation was that economic weapons were enough to strong-arm the likes of Kim, Khamenei and Maduro. He supposed that prosperity is their priority; it’s not. He waxed lyrical about the beach developments that North Korea could have. But these dictators don’t care about glitzy resorts. Their only interests are their own survival and that of their extreme ideologies.

Economic pressure sometimes works, of course. Mexico has made concessions to Trump to dodge sanctions, as did China. But for the hardest cases, it’s a poor substitute for a multifaceted foreign policy. That’s why “maximum pressure” will be an emblem of Trump’s tenure: a crude, half-baked strategy that was destined to fail.

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