After weeks of heightened tensions in the Persian Gulf, Britain said Thursday that one of its naval escorts had prevented Iranian vessels from blocking a British-flagged tanker. The tanker was attempting to pass the Strait of Hormuz — a key route for global oil exports — when the incident occurred.

Iran repeatedly threatened to close the strait in recent years but did not follow through. After the U.S. withdrawal from the Iran nuclear deal last year and amid suspected Iranian attacks on ships in the region in recent weeks, however, those threats began to carry a greater weight. When Iran acknowledged last month that it had shot down a U.S. spy drone, even a military escalation beyond the Strait of Hormuz appeared to be possible.

But on Thursday, Iran denied the British account of the latest incident, saying that its vessels had not challenged the tanker. The country’s foreign minister, Mohammad Javad Zarif, blamed Britain for what it said was an effort to “increase tensions” — an accusation the United States and other nations have similarly made against Iran.

The incidents in the Persian Gulf and in the neighboring Gulf of Oman have evoked memories of a prior “Tanker War” that occurred there.

“With mines exploding, insurance premiums soaring, and military vessels escorting tankers, the situation in the Persian Gulf and Strait of Hormuz today increasingly resembles parts of the Tanker War from the Iran-Iraq War era,” said Behnam Ben Taleblu, senior fellow with the Foundation for Defense of Democracies think tank, in an email. The bloody Iran-Iraq War from 1980 to 1988 also played out at sea, and hundreds of ships owned by or associated with the two sides were targeted in the conflict. Other ships were attacked, too.

Any attempt to block the Strait of Hormuz could easily escalate, experts said. “The U.S. is no longer as dependent on the flow of oil from the gulf as back then, but all of our allies are. So, for the functioning of the global economy, it’s still a vital waterway,” Nicholas Burns, a Harvard University professor and former undersecretary of state under President George W. Bush, said last month.

What happened in the 1980s confrontation?

The initial start of the sea conflict appeared to be slow and marginal, compared with the bloodshed on land: Iraq threatened to attack all ships going to or departing from Iranian ports in the northern part of the Persian Gulf in 1981, but it took until the following year for a Turkish oil tanker to become the first major vessel to be hit by an Iraqi strike. Unable to immediately match Iraq’s technical abilities to attack and sink ships, Iran later reciprocated.

Iran expert Gary Sick, who served on the National Security Council in the 1980s, emphasized the straightforward nature of those attacks at the time, both in terms of motivation and execution. Neither Iran nor Iraq made any secret of the fact they were waging a war of economic attrition, and they carried out their attacks with missiles and rocket-propelled grenades.

The United States became involved in the conflict in 1987, when it began escorting neutral Kuwait’s ships through the region to protect them from attacks. U.S. intervention ultimately helped end the conflict, after 37 U.S. crew members were killed when an Iraqi jet launched a missile attack against the USS Stark the same year.

What was the impact on the global economy?

Historical evidence from that period suggests that the most serious global repercussions had materialized long before U.S. involvement. Initially, in the early 1980s, “the Tanker War led to a 25 percent drop in commercial shipping and a sharp rise in the price of crude oil,” researchers with the University of Texas at Austin wrote. Prices also spiked because oil production itself was curbed after the Islamic Revolution in Iran in 1979.

One of the war’s paradoxes was that the more vessels were attacked, the more subdued was the reaction in the world economy. After an initial shock in the early 1980s, trading had resumed, and even at “its most intense point, the Tanker War failed to disrupt more than two percent of ships passing through the Persian Gulf,” wrote the University of Texas researchers.

Other countries increased their oil production in the following years to offset the impact of Iran’s Islamic Revolution. But another reason for the global oil market’s relative calm toward the end of the conflict was the realization that oil tankers are hard to sink.

On paper, the number of attacked vessels during the intensive phase of the conflict — from 1984 to 1987 — appeared significant enough to further disrupt global oil supplies.

Researchers later calculated the attacks sank or disabled less than a quarter of all attacked petroleum tankers.

Still, the conflict had a high price: Unable to match the Iraqi arms capabilities at sea, Iran began to target the crews of commercial vessels themselves. Hundreds of civilians were killed in both Iraqi and Iranian attacks.

How similar are today’s tensions and the 1980s Tanker War?

Analysts said there were some similarities between the 1980s confrontation and today’s tensions. “During the Iran-Iraq War, Iranian escalation in the Persian Gulf internationalized opposition to the regime,” Taleblu said. “Now, as Iran looks to throw its weight around in the Persian Gulf, it will likely drive more nations to embrace, rather than shun, Washington’s max-pressure strategy as the only way to deal with Iran.”

Others cautioned that growing pressure on Iran could make a repeat of the 1980s tensions more daunting. While the Tanker War of the 1980s was an extension of an existing war, today’s tensions at sea could become the trigger for one. Weapons systems are now more destructive and precise, and more easily available to Iranian forces. And this time, the United States has been a central player in the conflict from the beginning.

“It’s not that this is a difference between two other parties in the Gulf, and we are sort of bystanders,” Sick said.

This story was first published June 14. It was updated July 11.

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