Pulling the latest published assessment.
The Strait of Hormuz has been mined, escorted, threatened and fought over since 1984, yet it has never been shut. This timeline logs the incidents, seizures and agreements that moved the status needle, from the Tanker War to the interim passage window now in force.
War between the US, Israel and Iran cut daily transits by about 70 percent and put mines back in the approach corridors. A Muscat memorandum reopened fee-free passage in June under Iranian routing control, the arrangement still running today.
Iranian forces intercepted six merchant vessels using the Omani corridor and directed them back into the lanes Iran designates under the June memorandum. No damage or boarding was reported. Transit times on the affected legs rose by roughly four hours. Source: Reuters ↗
IMPACTAdded ~4 hours to affected transits and hardened routing compliance
A container ship grounded near Larak Island after transiting a route Iran had not approved. Salvage operations began the same week and both designated lanes remained usable throughout. No pollution was reported. Source: Lloyd's List ↗
IMPACTNo lane closure, but underwriters flagged off-route transits as a loss driver
A memorandum of understanding signed in Muscat opened a 60-day window in which merchant vessels transit without paying passage fees. Iran retains the authority to designate routing through the strait. The window is the reason the current status reads restricted rather than severely restricted. Our MOU explainer → Source: State Dept ↗
IMPACTTransits recovered sharply; war-risk quotes eased but stayed above pre-2026 levels
Iran turned down a France–Oman initiative to clear mines from the approach corridors. In the same week the IMO circulated a proposal for an alternative shipping lane off the Omani coast, which Iran declared void. No clearance work started. Source: IMO ↗
IMPACTKept mine risk unresolved and left routing entirely in Iranian hands
Reports of moored and drifting mines in the approach corridors circulated through naval and commercial reporting channels in the weeks after the war began. Owners held vessels at Fujairah and in the Gulf of Oman rather than transit. Daily transits stayed about 70 percent below the 2024 baseline. Transit volume data → Source: UKMTO ↗
IMPACTTransits held ~70% below baseline; war-risk cover repriced daily
Open hostilities started between the US and Israel on one side and Iran on the other. Iran announced control of the transit lanes within days. Daily transits fell by roughly 70 percent as owners suspended sailings. Source: AP ↗
IMPACTLargest single drop in transit volume recorded on this timeline
The Houthi campaign pushed container traffic around the Cape and made Hormuz the chokepoint with no alternative route. A twelve-day Israel–Iran war in 2025 brought widespread GPS jamming and the first parliamentary vote to recommend closing the strait.
Iran's parliament voted to recommend closing the Strait of Hormuz during the twelve-day war with Israel. The measure was advisory and was never enacted; the decision rests with the Supreme National Security Council. Traffic continued throughout. Source: Reuters ↗
IMPACTBrent spiked on the headline before retracing; no physical disruption
Twelve days of direct exchanges between Israel and Iran produced the heaviest electronic interference the Gulf had seen, with GPS jamming and spoofing reported across the strait and the Gulf of Oman. Several ships reported position errors of tens of nautical miles. War-risk premiums for Gulf calls rose sharply. Source: Windward ↗
IMPACTWar-risk premiums multiplied; some owners paused Gulf fixtures for days
IRGC forces boarded the container ship MSC Aries by helicopter near the Strait of Hormuz and took it to Iranian waters. The seizure came as regional tensions peaked and put box carriers, not just tankers, into the risk picture. The crew was held for weeks. Source: AP ↗
IMPACTContainer lines added Hormuz risk surcharges alongside tanker war-risk cover
A multinational escort operation was announced for the southern Red Sea after weeks of Houthi attacks. Most major container lines had already begun routing around the Cape of Good Hope. With Suez effectively bypassed, Hormuz became the chokepoint with no detour available. Source: US Navy ↗
IMPACTRaised the strategic weight of Hormuz without changing its own transit volumes
Houthi forces landed on the car carrier Galaxy Leader by helicopter in the southern Red Sea, opening a campaign against commercial shipping. The strait itself was unaffected, but Gulf trade began rerouting and repricing. Underwriters started treating the two waterways as one risk complex. Source: Reuters ↗
IMPACTStarted the reroute that made Hormuz the only chokepoint without an alternative
After the US left the nuclear deal, limpet mines, drone strikes and tanker seizures became a recurring feature of the Gulf of Oman approaches. Transits continued at close to normal volumes, but insurance, crewing and routing decisions were repriced around the risk.
Iranian naval craft intercepted the empty tanker Niovi as it transited from Dubai to Fujairah and escorted it into Iranian waters. It was the second seizure in a week. The US Navy said it observed the interception in progress. Source: US Navy ↗
IMPACTSecond seizure in seven days; escort requests to naval forces rose
Iran seized the crude tanker Advantage Sweet in the Gulf of Oman, citing a collision claim. The vessel had been chartered to lift Kuwaiti crude for a US refiner. It was held for months before release. Source: Reuters ↗
IMPACTCharterers began writing Hormuz seizure clauses into voyage terms
A drone struck the product tanker Mercer Street off the coast of Oman, killing two crew members. It was the first attack on Gulf-linked shipping in this period to cause fatalities. Investigators recovered drone debris from the vessel. Source: UKMTO ↗
IMPACTCrew-risk clauses tightened; Gulf of Oman transit premiums stepped up
A US strike in Baghdad killed the commander of Iran's Quds Force, and Iran struck back at bases in Iraq days later. Shipping in the Gulf braced for a maritime response that did not come. Owners slowed transits and some held vessels outside the strait for several days. Source: AP ↗
IMPACTWar-risk quotes for Gulf calls jumped; a brief pause in transit scheduling
The International Maritime Security Construct became operational in Bahrain, several months after the US announced Operation Sentinel. Its role was surveillance and reassurance rather than convoying every ship. Participation stayed narrow, with most European states staying out. Source: IMSC ↗
IMPACTRestored enough confidence to steady transit volumes through the winter
IRGC forces boarded the British-flagged tanker Stena Impero as it transited the strait and took it to Bandar Abbas. The seizure followed the detention of the tanker Grace 1 at Gibraltar two weeks earlier. The vessel was held for more than two months. Source: Reuters ↗
IMPACTUK-linked tonnage began transiting under naval escort
Authorities at Gibraltar detained the tanker Grace 1 on suspicion its cargo was bound for Syria in breach of sanctions. Iran called the detention piracy and warned of reciprocal action. The Stena Impero seizure followed within two weeks. Source: Lloyd's List ↗
IMPACTTriggered the tit-for-tat detentions that defined the 2019 risk picture
Iranian air defences shot down a US RQ-4A surveillance drone near the strait, with the two sides disputing whether it was over international or Iranian airspace. A US retaliatory strike was called off at short notice. The incident brought the confrontation closer to open conflict than any point since 1988. Source: AP ↗
IMPACTOil rose several percent on the day; some charters paused pending clarity
Two tankers, the Front Altair and the Kokuka Courageous, were damaged by explosions in the Gulf of Oman just outside the strait. Crews were evacuated and one vessel burned for days. The US attributed the attacks to Iran, which denied involvement. Source: Reuters ↗
IMPACTWar-risk premiums for Gulf voyages rose roughly tenfold within weeks
Four vessels at anchor off Fujairah were holed near the waterline in what investigators assessed as limpet-mine attacks. Fujairah sits outside the strait and is the main bunkering and loading alternative to Gulf ports. No casualties were reported. Source: UAE authorities ↗
IMPACTFirst repricing of Gulf war-risk cover since the JCPOA era began
Three decades in which the strait stayed open and closure was mainly a bargaining chip, invoked whenever sanctions tightened. Naval friction was frequent, but no incident interrupted the flow of roughly a fifth of world petroleum liquids consumption.
The US left the nuclear agreement and began reimposing sanctions on Iranian oil exports. Iranian officials again raised the possibility that no oil would leave the Gulf if Iran's own exports were blocked. The strait itself remained open and traffic was unchanged. Source: State Dept ↗
IMPACTSet up the maximum-pressure period; no immediate effect on transits
Iran and six world powers agreed the Joint Comprehensive Plan of Action, easing oil sanctions in exchange for nuclear limits. Closure threats dropped out of Iranian rhetoric for the next three years. Gulf war-risk premiums fell to their lowest level in a decade. Source: IAEA ↗
IMPACTLowest Hormuz risk pricing of the whole 1989–2018 era
Iran ran a ten-day naval exercise spanning the strait and the Gulf of Oman, including missile launches, as the EU moved toward an oil embargo. Washington said any interruption of transit would not be tolerated. Traffic ran normally throughout the drills. Source: Reuters ↗
IMPACTBrent added a risk premium of several dollars a barrel for weeks
Senior Iranian officials said the strait could be closed if sanctions cut off Iran's own oil exports. It was the most explicit closure threat since the Tanker War. No operational measures followed and transits continued at normal volumes. Source: Reuters ↗
IMPACTOil rose on the statement; freight and insurance largely unmoved
Several IRGC small craft manoeuvred aggressively around three US Navy ships transiting the strait, coming within a few hundred metres before turning away. The two governments gave conflicting accounts of radio traffic during the encounter. No shots were fired. Source: US Navy ↗
IMPACTNo commercial effect; established the fast-boat harassment pattern
Iraq's invasion of Kuwait put the northern Gulf back into a war-risk zone and removed Kuwaiti crude from the market overnight. The strait stayed open and loadings continued from Saudi and UAE terminals. Underwriters redrew Gulf war-risk boundaries within days. Source: Lloyd's List ↗
IMPACTWar-risk zone redrawn; strait transits continued without interruption
Iraq and Iran turned commercial shipping into a target set, and by 1987 the approaches to the strait were mined and patrolled by foreign navies. Traffic never stopped, but it moved in escorted convoys under war-risk premiums that repriced the whole Gulf trade.
The ceasefire under UN Security Council Resolution 598 took effect, ending eight years of war between Iran and Iraq and the attacks on shipping that came with it. Mine clearance in the Gulf ran on for months. Escorted convoys wound down over the following year. Source: UN ↗
IMPACTWar-risk premiums collapsed; normal unescorted transits resumed
The USS Vincennes, engaged with Iranian small craft in the strait, shot down Iran Air Flight 655 over the Gulf, killing all 290 people on board. The US said the airliner was misidentified as a military aircraft. It remains the deadliest single incident in the strait's modern history. Source: ICAO ↗
IMPACTMarked the peak of escalation before the ceasefire six weeks later
US forces destroyed two Iranian oil platforms used for surveillance and sank or crippled several Iranian naval vessels in reprisal for the mining of the USS Samuel B. Roberts. It was the largest US surface engagement since the Second World War. Iranian attacks on shipping fell away sharply afterwards. Source: US Navy ↗
IMPACTAttacks on merchant shipping dropped in the weeks that followed
The frigate USS Samuel B. Roberts hit a moored mine in the central Gulf, tearing a hole in the hull and injuring ten sailors. The crew kept the ship afloat and it was towed to Dubai. Recovered mines in the area matched Iranian stocks. Source: US Navy ↗
IMPACTTriggered Praying Mantis four days later; mine risk repriced Gulf-wide
US helicopters engaged and boarded the landing craft Iran Ajr as it laid mines in international waters near the convoy routes. Mines were recovered from the deck and the vessel was later scuttled. It was the first direct evidence tying Iran to the Gulf mining campaign. Source: US Navy ↗
IMPACTConfirmed a deliberate mining campaign; convoy escorts were reinforced
The reflagged supertanker Bridgeton struck a mine on the first Earnest Will convoy, holing a forward tank. The ship stayed afloat and led the escorting warships out of the danger area because none carried mine countermeasures. Minesweepers were rushed to the Gulf afterwards. Source: US Navy ↗
IMPACTExposed the escort gap and forced a mine-countermeasures deployment
Kuwaiti tankers were reflagged under the US flag and began transiting the Gulf under US Navy escort. It became the largest naval convoy operation since the Second World War. Escorted transits ran until well after the 1988 ceasefire. Source: US Navy ↗
IMPACTKept Kuwaiti crude moving, at convoy speeds and on naval schedules
Iran began attacking tankers serving Kuwait and Saudi Arabia in response to Iraq's campaign, widening the war to neutral shipping. Vessels calling at Gulf Arab terminals were now targets regardless of flag. Saudi air defences engaged Iranian aircraft over the Gulf in June. Source: Lloyd's List ↗
IMPACTWar-risk cover extended to all Gulf calls, not just Iranian and Iraqi ports
Iraq escalated air strikes on tankers loading at Iran's Kharg Island terminal, opening what became known as the Tanker War. Hundreds of merchant ships were hit over the following four years. Traffic through the strait continued, but crews and insurers began pricing the Gulf as a war zone. Source: Lloyd's List ↗
IMPACTFirst sustained targeting of merchant shipping in the Gulf
Traffic moving normally. Several major incidents sit at this level because the strait itself kept running.
Transits continue but under conditions — escorts, routing control, seizure risk or a war-risk surcharge.
Volumes materially down, with mines, active hostilities or lane control keeping owners out of the water.
Each era band shows the most disruptive level reached in that period, not its average.