Iran moves to block the Strait of Hormuz: What happens next
Oil prices spike, markets wobble as Iran votes to slam the gate on strategic waterway
On December 6, 1987, the Singapore-registered tanker Norman Atlantic went up in flames in the Strait of Hormuz after being attacked by an Iranian gunboat.
A few months later, in April 1988, amid the Iran-Iraq war, the US Navy’s USS Samuel B. Roberts (FFG-58) was badly hit by a naval mine as it passed through the Strait of Hormuz.
It blew an immense hole in the ship’s hull.
In retaliation, US forces launched “Operation Praying Mantis” hitting Iranian targets in the Arabian Gulf (read till the end to know on what happened next).
Would a similar incident play out now?
Hold on to your petrol receipts.
Iran’s parliament just gave the green light to close the Strait of Hormuz, pending final approval by the country’s Supreme Council — which, according to state-run Press TV, is expected to decide “soon”.
Already, merchant ships are steering clear of the strait amid the escalation of tensions between Iran on one side and Israel and the US on the other.
This narrow stretch of water is a key energy artery that moves 20% of the world’s oil per day — about $1 billion worth (yes, that’s daily), equivalent to ~17–20 million barrels/day and substantial LNG supplies.
Iran’s decision has rocked global oil markets. On Monday, Brent crude, the global benchmark, shot up to $77.36. WTI went up to $74.15, as per oilprice.com.
When oil jumps, inflation jitters follow.
Suddenly, the global stock markets do the see-saw shuffle.
Why does this tiny stretch of water matter so much?
Because Iran, a top oil producer, sits right next to it. And it's a narrow gate.
It’s like the landlord threatening to lock the front door on the world’s oil supply.
And now they’re saying they just might. Iran exerts influence via its coast.
Does Iran have the authority or legal right to block the strait?
No.
Under international maritime law, no country possesses legal authority to unilaterally close the strait.
How does maritime traffic work in this strait?
While the strait is relatively narrow (33 km), it is deep enough for VLCCs, or very large crude carriers to pass through unimpeded.
Ships follow a strict lane system: large tankers traverse two narrow shipping lanes.
How can Iran impose a blockade?
Iran can threaten movement with naval mines, small boat swarms or missile/drone strikes in the intervening “buffer zones”.
What do expert say about the threat?
A 2008 International Security study warned Iran that could have the capability to obstruct shipping for "up to a month" – unless forcefully countered.
Meanwhile, the US Congressional Research Service (CRS) and Washington Institute papers, put a spotlight on Iran’s “asymmetric warfare” in the Strait of Hormuz — with mines and swarm boats at the core.
Studies conducted by the Strategic Assessment and Center for Strategic & Budgetary Assessments outlined Iran’s Anti-Access/Area Denial (A2/AD) tactics, including mines, fast craft, and shore missiles. These are designed to complicate US and allied naval operations in the Gulf by creating asymmetric threats, saturating defence systems, and leveraging geography to deny freedom of manoeuvre in key chokepoints like Hormuz.
What triggered Iran’s decision to block Hormuz?
Early on Sunday (June 22, 2025), the US launched “Operation Midnight Hammer”, targeting three key Iranian nuclear sites — Fordow, Natanz, and Isfahan — with B‑2 stealth bombers, Tomahawk missiles, and among them 14 GBU‑57 bunker-buster bombs — the first combat deployment of these 14,000 kg (30,000‑lb) munitions.
What happens next?
And if Iran follows through with its decision, oil tankers may be forced to find an alternative route.
There’s just one problem: there isn’t one.
Naturally, oil prices did what oil prices do when threats like this surface — they spiked.
Countries that depend on imported oil, including China, India, and most of east Asia, could suffer economically.
On Sunday (June 22), US Secretary of State Marco Rubio urged China to help deter Iran from shutting down the Strait.
“I encourage the Chinese government in Beijing to call them about that because they heavily depend on the Strait of Hormuz for their oil,” Rubio said on Fox News.
What does history show?
Iran has often talked about closing Hormuz and has harassed or mined shipping.
But history shows it has never managed to shut this key waterway outright.
Reason: Sustained closure would be just as painful for Tehran as for the rest of the world.
Has Iran ever actually closed the Strait of Hormuz?
Short answer: No.
Tehran has threatened or tried to disrupt traffic several times, but it has never succeeded in sealing the waterway to commercial shipping.
The closest it came: the 1980-88 “Tanker War”.
Iran laid naval mines in and near the strait, fired Silkworm anti-ship missiles at tankers, used small fast-attack boats to harass vessels.
In response, the US re-flagged Kuwaiti tankers (“Operation Earnest Will”) and ran convoy escorts; mines were swept and traffic kept flowing.
While Iran damaged ships, it never stopped the oil stream.
Why did Iran fall short?
For one, Iran does not have the legal right under international law to block it.
On a practical note: Iran itself needed the strait for its own crude exports.
Moreover, the US Navy (and its allies) quickly counter-mined and escorted traffic.
The US Fifth Fleet (Bahrain-based) and allied navies have also maintained freedom of navigation patrols (FONPs).
After the Iran-Iraq war, the strait’s shutdown was a recurrent threat that never materialised.
In the 1990s, the chief of Iran’s Navy stated that the mission of their new Kilo-class submarines is to “control” the strait.
In response, US submarines and surface groups increased patrols.
Between December 2011 and January 2012, Iranian Parliamentarians vowed to “definitely” shut Hormuz if oil sanctions bit. There were Iranian war games and missile tests, but shipping continued.
In July 2018, Iran’s Revolutionary Guards Corps (IRGC) commander threatened to block all Gulf exports after US quit the Joint Comprehensive Plan of Action (JCPOA) – the Iran nuclear deal – a landmark agreement reached in 2015 between Iran and several world powers (including the US, UK, China, France, Germany, Russia, and the EU) aimed at limiting Iran's nuclear programme in exchange for sanctions relief.
There were short-lived exercises and a ballistic-missile test over the strait, but no closure.
What could Tehran try — and why is it hard?
Tools: mines, shore-launched missiles, swarming speedboats, mini-subs.
Challenges:
US-led naval coalitions can sweep mines and reopen lanes within days.
Blocking Hormuz would strangle Iran’s own oil lifeline and foreign-currency earnings.
US and its allies have assets in the region, and could bring more, to deal with Iranian military threat.
Moreover, oil buyers can divert via other pipelines that bypass the choke-point, as per a Reuters report.
Who’s the most affected?
Gulf oil producers: They will lose export capability, including Iran.
Import-dependent economies: East Asian nations feel energy disruptions swiftly.
Global markets: Higher crude costs reverberate across transportation, manufacturing, and inflation.
Shipping and insurance: Transit becomes riskier and costlier; insurers hike premiums.
The world will be watching
Meanwhile, satellite eyes are on Jask — a southern Iranian port town perched just outside the strait.
So, will Iran turn the Strait of Hormuz from a superhighway into a dead end?
Here's quick note on "Operation Praying Mantis": On April 18, 1988, US retaliation destroyed, damaged, or sank two Iranian oil platforms, three warships, several armed boats, and two fighter jets.
Two US Marine aviators died when their helicopter crashed into the Gulf.
This time, the world will be watching as oil traders and consumers sweat it out. If things heat up there, expect headlines, market swings, and petrol pump grumbles.
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