The Strait of Hormuz: A Timeline of Tensions

Portuguese explorers first reached the Persian Gulf in 1507 while sailing around Africa on the way to India. After capturing the small island of Hormuz, the Portuguese built a fortress and a customs house there to collect tolls from ships passing through the strait to trade in commodities like silk, spices, pearls and Arabian horses.

“Portuguese authorities issued ‘cartazas,’ as they called them—paid permission to trade in the Persian Gulf,” says Matthee, author of The Politics of Trade in Safavid Iran: Silk for Silver, 1600-1730. “Portugal made itself the tributary power in the region and became quite oppressive, so there was a lot of resistance against them.”

The Portuguese enriched themselves on trade through the Strait of Hormuz for a century until they were driven out in 1622 by an alliance between Abbas I, shah of Persia’s powerful Safavid dynasty from 1588 to 1629, and the English East India Company. The English provided the naval power in return for lucrative trading contracts with the Safavids.

After oil was discovered in Iran in 1908, the British played a leading role in exploiting the resource. The company that later became BP started out as the Anglo-Persian Oil Company, which won a lopsided deal in 1933 to control Iran’s oil exports.

In 1951, Iranian Prime Minister Mohammad Mossadegh announced that Iran was nationalizing its oil industry, which included the largest oil refinery in the world at the time at Abadan.

“Mossadegh, the prime minister, had the audacity to challenge the British by nationalizing the oil, arguing that it's our oil and we should profit more from it than the British,” says Matthee.

The British responded by sending the Royal Navy to establish a blockade around the port of Abadan and prevent any Iranian oil tankers from passing through the Strait of Hormuz. “The British choked off Iran’s access to the world, which was their main mechanism of enforcement,” says Matthee.

Mossadegh was defiant and became a national hero. Iranian protesters in support of Mossadegh drove away the shah, who was criticized as a puppet for Western oil interests in Iran. The British and Americans responded in 1953 with a CIA-backed coup that overthrew Mossadegh and reinstalled the shah. The result was an agreement that split oil profits evenly between Iran and Western oil companies.

U.S. diplomatic relations with Iran collapsed after the 1979 Iranian Revolution and the taking of 52 hostages at the American Embassy in Tehran. When Saddam Hussein of Iraq invaded Iran in 1980, the U.S. backed Hussein against their shared enemy.

The Iran-Iraq War raged for eight years and threatened to disrupt the movement of oil through the Strait of Hormuz. Oil tankers became targets for both sides. In 1984, Iraq attacked some Iranian oil tankers and Iran retaliated by laying naval mines in the Persian Gulf and harassing Iraqi, Kuwaiti and Saudi tankers with armed speedboats. During the so-called “Tanker War," the U.S. sent warships to escort neutral tankers safely through the Strait of Hormuz.

In 1988, an Iranian mine damaged the USS Samuel B. Roberts, a naval frigate on escort duty in the Persian Gulf. The U.S. responded with Operation Praying Mantis, a major military operation that sank or crippled much of the Iranian navy. Later that year, a U.S. warship accidentally shot down Iran Air Flight 655, killing all 290 civilians aboard the commercial flight.

Iran’s nuclear ambitions were born during the Iran-Iraq War, says Matthee, when the Iranian regime found itself increasingly isolated on the international stage. In the 2000s, Iran’s contested nuclear weapons program became the target of increasingly harsh economic sanctions from the U.S. and its European allies.

In 2008, Iran threatened to seal off the Strait of Hormuz if sanctions weren’t lifted, a move that U.S. authorities said would amount to an act of war. When the European Union announced a total embargo on Iranian oil in 2012, the Iranian regime once again promised to close the Strait of Hormuz, cutting off access to oil from all Persian Gulf nations.

In defiance of Iran, the U.S., France and Britain sent aircraft carriers and warships through the Strait of Hormuz, and Iran didn’t make good on its threat.

“There have been standoffs like this since the Iranian Revolution when the regime came into power,” says Matthee. “Iran's slogan from the very beginning was ‘death to America’ and ‘death to Israel,’ you know, this very revolutionary stance.”

The international shipping lanes through the Strait of Hormuz are very narrow and Iran claims the right to detain ships that enter Iranian waters—defined by Iran as anything within 12 nautical miles of its shoreline. From 2015 to 2024, Iran responded to U.S. sanctions and other international pressures by harassing and seizing international vessels in the Strait of Hormuz.

On April 28, 2015, Iranian patrol boats seized the Maersk Tigris, a Danish-owned oil tanker, after firing warning shots across its bow. Iran claimed it was part of a legal dispute with the ship’s owner. In 2019, a British-flagged oil tanker was also seized, allegedly in retaliation for an Iranian tanker stopped by the UK Royal Marines in the Strait of Gibraltar. And in 2024, Iranian special forces captured an oil tanker as part of a larger attack on Israel.

"Since 2021, Iran has harassed, attacked or seized nearly 20 internationally flagged merchant vessels, presenting a clear threat to regional maritime security and the global economy," the U.S. Navy reported in 2023.

With its geographic proximity to Iran, Israel has long been deeply concerned about the prospect of a nuclear-armed Iranian regime. On June 13, 2025, Israel launched massive airstrikes targeting military and nuclear sites in Iran, the first direct Israeli attack on Iranian soil. Iran responded with drone and missile strikes on Israel. Global oil prices spiked as investors worried that Iran would close the Strait of Hormuz.

The U.S. joined the fight on June 22, deploying B-2 bombers and “bunker-buster” bombs to hit underground Iranian nuclear sites as part of Operation Midnight Hammer. Iran promised a swift retaliation and launched rockets at U.S. bases in neighboring Qatar and Iraq.

After the U.S. strikes, the Iranian press reported that its parliament had voted to close the Strait of Hormuz to international oil shipments, but no such closure happened before a ceasefire was announced a few days later.

After decades of threatening to seal off the Strait of Hormuz, Iran finally took action in 2026 in response to large-scale attacks by the U.S. and Israeli militaries that killed Iran’s Supreme Leader Ayatollah Ali Khamenei.

"The strait (of Hormuz) is closed. If anyone tries to pass, the heroes of the Revolutionary Guards and the regular navy will set those ships ablaze," said a senior adviser to the Islamic Revolutionary Guard Corps on March 2, 2026.

Iran made good on its threat by targeting ships and freighters in the Strait of Hormuz with drones and missile strikes. The closure choked off oil exports from Iraq, Kuwait, Qatar, Saudi Arabia and the UAE, and sent global oil prices skyrocketing.

“The Iranian regime has been preparing for an ultimate attack by Israel or the United States for a long time, so it's not that surprising that they didn't simply roll over and surrender unconditionally,” says Matthee. "Their whole existence is premised on this idea of defiance of the West and in a way, the world.”