“We’re out of the deal. We’re out of the deal.” That was national security advisor John Bolton’s summary of President Donald Trump’s decision over the nuclear agreement with Iran. Over the next six months, the sanctions that the deal waived and revoked will roll back into place. Iran’s response remains to be seen. President Hassan Rouhani stated that Tehran would hold discussions with the remaining parties to the deal on paths forward; if Iran’s national interests are secured, they’ll remain, “but if the nuclear deal turns into a mere document under which Iran’s national interests are not taken into account, then our decision will be clear.” Rouhani also directed Iran’s Atomic Energy Organization to be ready to resume “industrial [uranium] enrichment without restriction.” Trump, for his part, said he was “ready, willing, and able” to negotiate “a new and lasting deal.”
Such a deal will be a long time coming, if it comes at all. The restored sanctions will only be fully in place by the midterm elections, and may take longer to bite. The original nuclear deal took years to realize even after the strongest sanctions were put in place. The original sanctions had support from key Iranian trading partners in Europe, and were helped along by then-president Mahmoud Ahmadinejad’s severe economic bungling. The broader deal Trump seeks, if talking points circulated by the White House reflect the president’s convictions, will require Iran to make the sorts of steep concessions usually only offered by states defeated in war. The odds are long.
We are giving up a fine bird in the hand for those two in the bush. The deal itself was fairly solid—serious restrictions on Iranian enrichment capacity, uranium stockpiles, enrichment levels, pathways to plutonium, and enrichment methods, coupled with implementation (though not guaranteed ratification) of an Additional Protocol monitoring agreement with the International Atomic Energy Agency. No state of the 129 with an Additional Protocol has ever acquired nuclear weapons.
The Trump administration had inadvertently made the deal better still with its many months of ambiguity. Iran’s desire to keep America in the deal and the Europeans off America’s side must have had something to do with the sudden and sustained end to Iranian harassment of U.S. Navy vessels in the Persian Gulf. American troops have largely been safe from Iranian militia violence in Syria and Iraq, and Iran hasn’t made a serious attempt to retaliate against Israel for repeated strikes on Iranian assets in Syria.
The benefits of Trump’s ambiguity stood to grow. There are many points of friction between America and Iran these days, and many are getting worse. Iran-friendly militias in Iraq have been warning for months that they might take action against America’s presence there now that ISIS is on the ropes. It’s a similar story for U.S. troops in Syria. Iran’s puppet Hezbollah had a strong showing in Lebanon’s elections last weekend; Iran’s friends in Iraq have their turn at the polls this weekend. Israel’s northeastern frontier is poised to explode—shortly before Trump’s speech, residents of the Golan were warned to prepare bomb shelters due to unusual Iranian movements. The loss of ambiguity may make war there more likely.
Trump’s decision makes a direct U.S.-Iranian war more likely, too. Iran now has less to lose in its relations with America, and less incentive to avoid negative and inflammatory actions that could contribute to crises. If the deal continues to fall apart and Iran resumes significant uranium enrichment, the pressure will grow on the United States and Israel to attempt to destroy the nuclear program. In the tense days before the last round of negotiations began in earnest, U.S. Central Command analysts were reportedly even watching moon phases in an attempt to anticipate the night of an imminent Israeli strike. Improvements in Iran’s defenses and options against Israel since then have made it more likely that the task would instead fall to America. And a strike, mind you, might only delay the Iranian nuclear program, meaning later strikes could follow—a process Israeli analysts describe as “mowing the lawn.” The strongest criticism of the nuclear deal had been that it only delayed an Iranian bomb. But unlike strikes, the deal didn’t kill anyone, cost anything, or risk a wider war.
Trump’s withdrawal from the deal wasn’t his only option for taking action against it. He could have stayed in without sitting on his hands. A deep report by Washington Institute Iran policy wizard Patrick Clawson highlighted the many points of presidential discretion in the array of sanctions laws that apply to Iran. Trump could have refrained from waiving sanctions—all he had to do this week—and perhaps applied a few new measures. He could have worked methodically, increasing pressure step by step, creating uncertainty, steadily building pressure on Iran while preserving the pacific incentives ambiguity created. This would have violated the deal, but America would have retained access to several key levers against Iran. It would still have been a member of the deal’s Joint Commission mechanism, which would have allowed it to pursue possible Iranian violations. And Washington would have had the option of triggering, on its own, UN sanctions against Iran via Security Council Resolution 2231. (The 2231 mechanism is restricted to participants in the deal; Bolton explicitly stated that Treasury guidance around the mechanism wasn’t applicable “because we’re out of the deal.”) 
Full U.S. withdrawal takes these options off the table.
Where will things go from here? Watch Brussels. Henry Kissinger in his Arab-Israeli diplomacy days used to say that there could be “no war without Egypt, and no peace without Syria.” In nuclear talks with Iran, there can be no decisive impact without Europe, and no settlement without America. Europe is the pivot player. Iran wants to do business with Europe; even with the nuclear deal, much U.S. business with Iran was illegal. Trump will either need to get Europe on board with new sanctions that hurt European businesses, or he will need to target European companies himself, creating a serious diplomatic crisis. (The middle path, sanctioning Iran unilaterally while letting Europe slide, would significantly reduce pressure on Tehran.) Europe so far has shown no appetite for putting fresh pressure on Iran. And all this, again, is for the chance of creating enough leverage to begin broader negotiations, and comes at real technical and strategic cost. One thing alone is sure: Iran’s main strategic goal on the nuclear issue has been achieved. America and Europe are split, and the UN sanctions are off. Now Tehran can choose whether it would like an enriched cherry on top.
John Allen Gay is executive director of the John Quincy Adams Society and coauthor of the 2013 book War with Iran: Political, Military and Economic Consequences.