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Why are the US and Iran at war, and what is happening in Hormuz?

What began as US and Israeli strikes on Iran in February is now in its eighth month, with oil at a five-month high. The fighting has shifted to a narrow waterway that carries about a fifth of the world's oil, and a US election date now shapes the timing.

Published 22 Oct 2026 Updated 23 Oct 2026 By Implica 24 sources 9 min read

THE SHORT ANSWER

The reports so far do not give one stated reason for the US and Israeli strikes that began the war on 28 February 2026, but the quarrel sits on decades of hostility over oil, sanctions and Iran's nuclear programme. Iran answered by asserting control of the Strait of Hormuz, the Gulf's only sea exit. The US answered with a blockade of Iranian ports and sanctions. Both sides now press each other through shipping, and talks have not ended the fighting.

What happened

On 20 October, Iran's Revolutionary Guard, a powerful branch of its armed forces, said mines it laid in the southern part of the Strait of Hormuz exploded under two oil tankers, setting both ablaze. It named neither ship. On 22 October, Iranian state television said seven tankers had caught fire or hit mines overnight. The Guard's navy said four caught fire while transferring oil and three were immobilised by mines. The Associated Press could not confirm this, and the British military monitor UKMTO did not report the attacks. If true, it is the most vessels hit in a single day since the war began.

President Donald Trump said on 22 October that Iran was making up "fake hits" to push up oil prices before the US midterm elections on 3 November, and that more oil was passing through Hormuz than before the conflict. Data provider Kpler had reported crude exports through the strait at 82% of pre-war levels as of Sunday 18 October, but refined products such as petrol at only about 44%. The US Navy has been escorting civilian ships along a southern route near Oman. Iran calls that route illegal.

Diplomacy is stuck. Iran has proposed that it reopen the strait and resume nuclear talks within a week, in return for an end to the US blockade, eased limits on its oil sales and a restored ceasefire. Its foreign ministry called the US reply "insufficient and incomplete". Iranian officials told Reuters they expect bombing to resume. On 23 October Iran said it would hit Gulf oil facilities, undersea cables and datacentres if the US and Israel attack again, and Brent crude, the global oil benchmark, reached $114.72 a barrel, its highest since May.

Why it matters

The Strait of Hormuz normally carries about 20% of global oil supplies, so attacks there raise fuel prices far from the region. Before the war Brent traded around $72 a barrel. It hit $126 at the end of April. Fuel costs are now a top issue in the US midterms, and the UN trade body UNCTAD has cut its 2026 world growth forecast to 2.6%, blaming the energy shock.

  • For ship crews and owners, The UN has logged 106 confirmed incidents and at least 24 seafarer deaths since the war began. Two ships have been sunk, the latest the container ship GFS Pride on 14 October.
  • For drivers and governments, US regular gasoline averaged $4.32 a gallon on 16 October, and US diesel is up 70% since the war began. The UN says fuel subsidies are on track to exceed $1 trillion this year.
  • For firms that trade with Iran, The US has sanctioned companies and ships in Turkiye, China, the UAE, the UK, the Marshall Islands and India. Treasury says about 20 million barrels of Iranian oil are stranded at sea.
  • For poorer countries, G7 finance ministers pledged to mobilise $2.5 billion, mostly for fertiliser, because the World Bank has identified 44 countries that may face food security problems.

The background: seventy years of oil, sanctions and mistrust

Oil, a coup and an alliance (1951 to 1978)

In 1951 Iran nationalised its oil industry, seizing the assets of the British-owned Anglo-Iranian Oil Company. Mohammad Mosaddegh became prime minister that April. In 1953 the US and Britain, through the CIA and MI6, orchestrated a coup that removed him. It failed at first and succeeded on a second attempt, and it put Shah Mohammad Reza Pahlavi back in power.

The Shah then became a close US partner. In 1953 the US launched Iran's nuclear programme under its Atoms for Peace scheme, and in 1967 it supplied the Tehran Research Reactor and 5.58 kg of enriched uranium. Iran signed the Treaty on the Non-Proliferation of Nuclear Weapons, which bars states from building nuclear weapons, and ratified it in 1970.

Revolution and naval clashes (1979 to 1988)

The Iranian Revolution of 1978 and 1979 ousted the Shah and brought Ayatollah Ruhollah Khomeini to power. On 4 November 1979 students seized the US embassy in Tehran and held 52 American diplomats for 444 days, after the US admitted the deposed Shah.

Shipping became a target in the Iran-Iraq War. From May 1981 Iraq attacked commercial ships, and Iran retaliated against the vessels of Iraq's trading partners. On 18 April 1988 the US Navy struck Iranian targets in Operation Praying Mantis, in retaliation for Iran mining the Persian Gulf. On 3 July 1988 the USS Vincennes shot down Iran Air Flight 655, killing 290 people. The US later said it was an accident.

Sanctions and the nuclear deal (1995 to 2025)

In April 1995 President Bill Clinton imposed a total oil and trade embargo on dealings with Iran by American companies. In 2015 Iran and world powers agreed the Joint Comprehensive Plan of Action, which limited Iran's enrichment and stockpile in return for sanctions relief. Nuclear sanctions were lifted on 16 January 2016.

On 8 May 2018 the US withdrew from the deal under Trump and reinstated sanctions as a policy of maximum pressure. In July 2018 Iran threatened to close the strait. On 13 June 2019 two tankers were hit by explosions there, and the US blamed Iran, which denied it. A 2019 US estimate said Iran had over 5,000 naval mines. In June 2025 Iran reportedly threatened to block the strait after Israeli attacks on its military and nuclear sites. Before 2026 the strait had not been closed for any extended time.

War, blockade and a failed deal (February to September 2026)

On 28 February 2026 the US and Israel launched a large-scale joint military operation against Iran. Iran asserted control of Hormuz soon after. The US imposed a naval blockade of Iranian ports on 13 April and suspended it on 18 June, a day after the Islamabad Memorandum of Understanding set a temporary framework to end military operations and reopen the waterway. Trump said on 3 July that Iran had agreed to US demands. The memorandum collapsed, the reports so far do not say why, and the blockade returned on 14 July.

Talks stalled over Iran's demands for sanctions relief and reparations. Strikes resumed. On 1 September the US bombed Revolutionary Guard sites and two supertankers were hit fleeing the strait. On 9 September the US destroyed five Iranian tankers near Kharg Island after Iran targeted a US warship. Treasury also widened its sanctions campaign, Operation Economic Outcast.

October 2026

Iran hit seven tankers in five days in early October. On 8 October Trump said the US would not attack before the midterms, while keeping the blockade. Treasury sanctioned 27 companies, six individuals and 22 vessels that day. Attacks surged afterwards, and UKMTO says October has had the most reported attacks on shipping since March. Analysts and an Arab diplomat quoted by The Washington Post say Iran is trying to punish Trump at the polls. Iranian officials told Reuters they expect bombing to resume sooner or later.

GOOD TO KNOW

Onshore pipelines can carry only about 3 million barrels of oil a day, while about 15 million barrels a day were moving through the Strait of Hormuz by 2025.

Why does the Strait of Hormuz matter so much?

The strait lies between Iran and Oman's Musandam Peninsula, and it is the only sea passage from the Persian Gulf to the open ocean. It is about 104 miles long and 24 miles wide at its narrowest. Iraq, Kuwait, Qatar, Bahrain and the UAE depend on it, and all liquefied natural gas from the Gulf must go by ship through it.

Pipelines can carry only part of the load: onshore pipelines have a maximum capacity of around 3 million barrels a day, against about 15 million barrels a day through the strait by 2025. Middle East exports still reached 16.5 million barrels a day in September, though 40% of that now bypasses the strait.

What are the blockade and the sanctions meant to do?

The blockade is a US naval cordon around Iranian ports. US Central Command says it has redirected 138 commercial vessels since it resumed on 14 July. Sanctions target the ships, firms and banks that move Iranian oil, including the ageing tanker network known as the shadow fleet. Treasury says the combination has halted Iranian crude loading and unloading.

Iran says lifting the blockade and ending the war on all fronts are legitimate demands. It has also said it will not abandon uranium enrichment, so the nuclear question stays tied to any deal on Hormuz.

Timeline: 1951 to today

OIL, COUP AND REVOLUTION

  1. Iran nationalises its oil industry, seizing the assets of the Anglo-Iranian Oil Company.

  2. The US and Britain orchestrate a coup that removes Prime Minister Mosaddegh and restores the Shah.

  3. The US supplies Iran's first nuclear reactor and 5.58 kg of enriched uranium.

  4. Students seize the US embassy in Tehran after the revolution and hold 52 diplomats for 444 days.

  5. The US Navy strikes Iranian targets in Operation Praying Mantis, after Iran mines the Persian Gulf.

SANCTIONS AND THE NUCLEAR DEAL

  1. President Clinton imposes a total oil and trade embargo on US dealings with Iran.

  2. Nuclear sanctions on Iran are lifted under the 2015 nuclear deal.

  3. The US withdraws from the deal and reinstates sanctions.

  4. Two tankers are hit by explosions near the strait; the US blames Iran, which denies it.

  5. Iran reportedly threatens to block the strait after Israeli attacks on its military and nuclear sites.

THE WAR

  1. The US and Israel launch a large-scale joint military operation against Iran, and Iran asserts control of Hormuz.

  2. The US imposes a naval blockade of Iranian ports.

  3. The Islamabad Memorandum of Understanding sets a temporary framework to end military operations; the blockade is suspended the next day.

  4. The US reinstates the blockade after the memorandum fails to hold.

  5. Oil heads for a 20% monthly surge as renewed strikes widen the war.

  6. Oil passes $85 as a Hormuz reopening deal stalls over Iran's demands for sanctions relief and reparations.

  7. The US bombs Revolutionary Guard sites and two supertankers are struck fleeing the strait.

  8. The US destroys five Iranian tankers near Kharg Island after Iran targets a US warship; Brent tops $100.

OCTOBER 2026

  1. Iran is reported to have hit seven oil tankers in the strait in five days.

  2. Middle East oil exports are reported back at pre-war levels in September, with 40% bypassing Hormuz.

  3. Trump rules out striking Iran before the 3 November midterms, and Treasury sanctions 27 firms and 22 vessels.

  4. The container ship GFS Pride sinks in the strait; Singapore reports a projectile and Iran's Guards say a mine.

  5. Iran says its mines set two tankers ablaze in the southern lane.

  6. Iran says seven ships were struck in a night, and Brent rises to its highest since May.

What to watch next

  • The 3 November midterms. Trump has said the pause on striking Iran is not a settlement and that he may resume full-scale operations after the vote.
  • The US reply to Iran's proposal. Iran's seven-day offer to reopen the strait and restart nuclear talks awaits an answer that Tehran does not call insufficient.
  • Iran's threats to Gulf infrastructure. Iran says it would hit Gulf oil facilities, undersea cables and datacentres if the US and Israel attack again.
  • Verification of the tanker attacks. The seven-ship claim of 22 October has not been independently confirmed, and the UN and UKMTO figures will show how the shipping campaign develops.

Sources

How this article was made: Implica's editorial system wrote it from the news reports above, with the background drawn from Wikipedia: Iran–United States relations, Iranian Revolution, Iran nuclear deal, Strait of Hormuz.

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