Iran Blockade Sets Up a Test of Which Side Can Endure More Pain

President Trump’s decision to blockade all Iranian shipments out of or into the Strait of Hormuz starting Monday morning sets up the next great test in the Iran war: Which side can endure more economic pain, Tehran’s new leadership or Mr. Trump himself?

Almost everything about how this new turn in the war plays out is likely to look very different than what has unfolded so far.

Instead of directing missiles and bombs at military sites, missile emplacements and Iran’s defense industry, Mr. Trump will try to choke off the country’s lifeblood, the oil that accounts for more than 50 percent of its exports and just about all of the government’s revenue.

The president’s first hope, administration officials said on Sunday, is to force the government to surrender to the terms that Vice President JD Vance laid out in peace talks in Islamabad, Pakistan — and that Iran rejected, just as it did in negotiations in Geneva before the war began on Feb. 28. The list of terms starts with Iran’s agreement to turn over every ounce of its uranium stockpile, permanently dismantle its huge infrastructure for producing nuclear fuel and give up its claims to regulate traffic in the strait.

Failing an Iranian capitulation, Mr. Trump appears to still harbor the hope he expressed the first evening of the war: that a restive Iranian populace will rise up and overthrow the military-clerical regime that has guided the country since the revolution in 1979. But engineering that outcome is no easier than it was a month and a half ago.

For its part, Iran’s strategy appears to be one of waging the conflict in the global markets, where Tehran has discovered new powers. Acutely aware that they lost the military contest in the first five weeks, but performed above expectations in the information arena and in terrorizing their neighbors with well-aimed missile and drone strikes, the Iranians are betting that Mr. Trump’s tolerance for political pain is limited.

If no Iranian oil gets through the strait, prices could keep rising over time — some companies say they are planning for $175 a barrel. The Iranians understand the potential political effects of continued inflation in the United States less than seven months before midterm elections.

“Soon you’ll be nostalgic for $4 to $5 gas,” Iran’s top negotiator and the speaker of its Parliament, Mohammad Bagher Ghalibaf, warned American consumers after the failure of the talks he led with Mr. Vance. As of Monday morning, with the naval blockade about to begin, the markets did not seem especially panicked: Brent crude oil prices rose about 6 percent, to just above $101 a barrel, but were still below where they were before the cease-fire was declared last week.

Mr. Trump, for his part, is dialing back his previous claim that as the shooting stops, gas prices will drop. He told Fox News on Sunday that prices “should be around the same” during the midterms and might be “a little bit higher.” That is the exact fear of many Republican candidates.

This is uncharted territory. Like President John F. Kennedy’s “quarantine” of Cuba in 1962, intended to keep the Soviets from bringing nuclear weapons onto Cuban soil, it is impossible to know beforehand how this will play out. Back then, Kennedy and his advisers watched anxiously to see if the Soviets would try to “run the line” and risk military confrontation with the U.S. Navy or whether they would retreat, negotiate and find a face-saving way out.

The Soviet leader at the time, Nikita Khrushchev, chose to back off.

After the blockade on any ships leaving or destined for Iranian ports goes into effect, at 10 a.m. Eastern on Monday, it may become clear whether the new ayatollah, Mojtaba Khamenei, and the Islamic Revolutionary Guard Corps make the same choice. But without a navy, Iran knows it has virtually no chance in a direct confrontation.

For Mr. Trump, this is yet another reversal of strategy. A few weeks ago, he decided to allow Iran to sell oil that was already at sea, in hopes of easing supply shortages. But the effects on prices were minimal. And Mr. Trump looked as though he were conducting a halfhearted war, bombing Iran while allowing it to profit. And the country’s imposition of tolls on traffic going through the strait meant that a new revenue stream was opening up for Tehran at the moment it needed it most.

“The current situation, in which Iran gets to deny use of the strait to all except its friends or those who pay up, is untenable,” said Richard Haass, a former Republican senior national security official and the former president of the Council on Foreign Relations, who was among the first to advocate a blockade strategy.

“It gets rich while others get poor,” he continued. “A blockade adds to the economic pressure on Iran that already existed before the war and was made worse by the war. If they want to sell their oil, they need to reopen the strait to all.”

The test of the strategy may well be how Iran’s biggest customers react. Mr. Haass argues for pairing the blockade with a diplomatic strategy to get China, India, Pakistan and Turkey — all major customers of Iran — to pressure the country to give in to U.S. demands and get oil flowing again. But it is unclear whether they will do so, especially if China sees an opportunity to profit in the long term from the confrontation.

Mr. Haass also said that “we should couple the threat or reality of a blockade with a proposal to establish new governance authority for the strait that would include Iran,” giving it a voice — but not control — over governance of the waterway.

It might work. But there is also the possibility that Iran’s reaction will be to resume attacks on energy facilities in the United Arab Emirates, Kuwait and perhaps even Saudi Arabia. In that scenario, Iran would essentially say that if it cannot ship oil, its Arab neighbors will not be able to, either.

As with so much in this war, there was confusion on Sunday about what, exactly, was subject to blockade. Mr. Trump’s social media post declared a “complete” blockade on all traffic in and out of the strait. But as described in a news release on Sunday from U.S. Central Command, the blockade applies only to ships going to or from Iranian ports. Cargo from other Gulf states will be allowed to pass, assuming they are willing to take the risk of hitting mines or being attacked by Iranian speedboats or drones. It was also unclear how the United States would determine which ships had paid a toll to the Iranians.

The strait has been shuttered before, of course, but history does not provide much guidance that fits the current situation.

As Mr. Haass, along with the historians Niall Ferguson and Philip Zelikow noted in The Free Press last week, the Portuguese first took control of the strait 519 years ago and charged a toll. They were ousted by Persian and British forces. Half a millennium later, the Portuguese and the British made clear that the attack on Iran, even in the name of preventing it from getting within reach of a nuclear weapon, was ill considered.

In the early 1950s, Britain blockaded the strait after Iran’s prime minister at the time, Mohammad Mossadegh, nationalized the country’s oil industry. He was overthrown in a coup that was partly supported by the C.I.A., a covert intervention that the Iranians resent to this day and that history has not treated kindly.

And there were episodic disruptions during the Iran-Iraq war in the 1980s.

But none of those experiences is a very close analog to the complex confrontation that is currently unfolding. If the blockade is short-lived and ends Iran’s ability to extort the global economy, Mr. Trump’s gamble may well look like a savvy turning of the tables. And if the Iranian leadership gives in to his demands, it may ratify Mr. Trump’s conclusion that the new leadership is more “reasonable” than the last.

If the blockade drags on, though, Mr. Trump runs the risk of looking once again as though he failed to see around corners, anticipating what could go wrong with an attack on what appeared to be a weakened Iran. The war that he thought might last only days is entering its seventh week. And for the global economy, the hard part is not close to over.

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