With his decision to pull out of the Iran nuclear deal, President Trump has committed his most irresponsible act in foreign policy to date.

The move—which Trump took against the urgings of European heads of state, Israeli security officials, dozens of current and former diplomats, his own secretary of defense, and even the conservative chairman of the House Armed Services Committee—can only be attributed to one or more of three motives: a misunderstanding of the deal’s terms, a need to torpedo yet another one of President Obama’s accomplishments, or a desire to weaken or destroy the government of Iran.

Trump claimed in his televised speech today that Iran is cheating on the deal, but his own intelligence directors have said there is no evidence of this claim whatsoever. The International Atomic Energy Agency has certified Iran’s compliance 10 times since the deal was signed. Secretary of Defense James Mattis testified to a Senate committee last month that, after reading the 140-page agreement three times, he was struck by how “robust” the deal’s verification provisions were.

It’s also the case that the most influential backers of Trump’s decision—Israeli Prime Minister Benjamin Netanyahu, Secretary of State Mike Pompeo, national security adviser John Bolton, and the Sunni Crown Prince of Saudi Arabia—are fervent advocates of regime change in Iran, by force if necessary.

From early on in his presidential campaign, Trump promised to kill the accord, which he has repeatedly called “the worst deal” ever “drawn up by anybody.” Here is where ignorance enters the picture. As evidence of his charge, Trump used to claim that the deal required us to pay Iran $100 billion—when, in fact, it merely required us to return Iranian assets that we’d frozen. (Also the $100 billion is a rough estimate of assets frozen not just by the U.S. but worldwide.) Far from a bad deal, this seemed like a fair trade: We had frozen their assets as punishment for their illegal nuclear program; therefore, in exchange for dismantling the program, we would unfreeze the assets.

Trump has also complained that the deal has not stopped Iran from testing ballistic missiles or supporting terrorists. In fact, the deal’s negotiators made no claims that it would—any more than U.S.–Soviet arms-control treaties during the Cold War blocked Moscow from various activities that threatened U.S. interests. Besides, several existing sanctions related to Iran’s ballistic missiles and support for terrorist movements remained active after the deal went into effect.

Finally, Trump complained, as have many other critics, that the deal—which was signed in 2015 by Iran, the United States, and five other countries (France, Britain, Russia, China, and Germany)—expires in a mere 10 years after the deal’s signing, at which point Iran could simply resume its nuclear ambitions. It’s true that some of the deal’s aspects expire in 2025—the ban on production of advanced centrifuges, the monitoring of Iran’s civil nuclear procurement, the automatic U.N. “snapback” of sanctions if Iran cheats. But many other restrictions hold until 2030. These include the 3.67 percent cap on enriched uranium (far below the level of enrichment necessary for bomb-grade material), the stockpile gap on that level of low-enriched uranium (meaning that even if they enriched it to weapons-grade levels, they wouldn’t have enough to turn it into a bomb), and the ban on heavy-water reactors (which would be needed to turn the uranium into a bomb). More important still, international inspectors are allowed to keep intrusively monitoring centrifuge production until 2040. And other pledges that Iran made in the agreement—to permit other sorts of inspection, to reprocess spent fuel (rather than turn it into weapons), and to continue abiding by the Non-Proliferation Treaty—have no expiration date.

This is the main problem with pulling out of the deal, the problem that has made even many critics of the deal urge Trump to stay in: Once the deal is undone, Iran has no obligation to keep hosting the inspectors. It is a long-established fact that Iranian scientists know how to build an atomic bomb. (The trove of 15-year-old documents that Netanyahu theatrically revealed last week—and which Trump cited as the basis for his charge that Iran is cheating—was, in that sense, nothing new, and contained nothing suggesting that Iran is pursuing a nuclear weapon now.) The deal gives international inspectors intrusive powers to ensure that those scientists aren’t acting on their know-how. Without the deal, they have no such powers. The Iranians once did have a secret nuclear program; without the deal in place, they can restart it, without notice by outsiders.

And the U.S. withdrawal from the deal means the deal is very likely dead. Reimposing sanctions on Iran would also entail reimposing “secondary sanctions” on banks and other enterprises that do business with Iran. Most foreign companies, faced with the choice of forgoing deals with Iran or ending deals with the United States, would choose the former. (Russia and China might prove exceptions, in which case Trump’s move would benefit them.)

The European signatories have declared in recent days that they will stay in the treaty and encourage Iran to do the same. European Union officials added today, in advance of Trump’s announcement, that they would try to protect companies that continued doing business with Iran. Colin Kahl, a former Obama administration official, said in an email that the EU could compensate those companies for their losses caused by U.S. secondary sanctions; they could even threaten retaliation against the United States and take the Trump administration to the World Trade Organization to deter full enforcement of those sanctions.

That would be quite an escalation in trans-Atlantic tensions, but U.S. allies might have determined by now that as long as Trump is president, they have little to gain from cooperation with Washington when their own notions of security and global interests are at stake.

The withdrawal might also compel Iran to resume its nuclear program—this time, with no outside inspectors. For some time, hard-line factions in Tehran have been grumbling that the deal has given them little in economic benefits—mainly because businesses have shirked from investing much in Iran, fearing that they might have to abandon their stakes if Trump pulled out of the deal and reinstated sanctions. Now that Trump has done just that, the hard-liners are no doubt chortling.

So Trump has wrecked one of the most successful arms-control deals in modern history, destroyed any possible leverage to negotiate a new one, further disrupted unity with our allies, further damaged U.S. credibility, strengthened hard-line factions in Iran, exacerbated instability in the Middle East, and possibly boosted the chance of war—which some of Trump’s abettors desire. Quite the deal-maker.