23JUL

GPS blacked out across Gulf chokepoints

2 min read

19:27UTC

US and British maritime authorities confirm an electronic warfare corridor stretching 2,500 kilometres across two of the world's three critical sea lanes. There is no safe detour.

← Back to Second chokepoint doubles Med freight Jump to analysis ↓

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Key takeaway

An electronic warfare corridor now links two chokepoints, leaving no safe maritime alternative.

MARAD Advisory 2026-004 and UKMTO data confirm severe GNSS/GPS interference extending from the strait of Hormuz across the Gulf of Oman and into the Red Sea near Bab al-Mandeb ¹. This is not a side effect of military operations but a deliberate electronic denial zone spanning two of the world's three critical maritime chokepoints.

No modern peacetime precedent exists for electronic warfare denial at this scale. During the Tanker War (1987 to 1988), mines and missile boats threatened individual vessels. The current denial threatens the navigational infrastructure itself, degrading the ability of any vessel to determine its own position across a 2,500-kilometre corridor. The Houthis threatened Bab al-Mandeb closure the day after Pakistan confirmed talks had stalled.

Vessels diverting from Hormuz toward the Red Sea now navigate degraded positioning systems approaching a second contested chokepoint. Roughly 4.5 million barrels per day and 12% of global trade pass through Bab al-Mandeb. Combined with near-total Hormuz closure, the world's two most important oil chokepoints are under simultaneous pressure for the first time since the 1973 oil crisis ². The Cape of Good Hope route adds 10 to 14 days and $500,000 to $1 million per voyage in fuel costs.

Deep Analysis

In plain English

Ships navigate using GPS-style satellite signals. Someone is deliberately jamming those signals across a 2,500-kilometre corridor stretching from the Strait of Hormuz in the Gulf to the Bab al-Mandeb in the Red Sea. This matters because ships diverted away from Hormuz (which Iran controls) have been heading toward the Red Sea instead. The GNSS jamming makes that alternative route significantly more dangerous, because ships cannot accurately determine their own position. The practical effect: there is now no safe, insurable sea route between the Gulf and global markets. Ships must go around Africa instead, adding 10 to 14 days and significant fuel costs to every voyage.

Source Landscape

This story draws on neutral-leaning sources

Primary parallel: The Tanker War of 1987-88 saw Iran and Iraq attack vessels in the Gulf, leading to Operation Earnest Will — US Navy convoy protection through Hormuz. The threat was kinetic and localised. The current electronic denial operates across a 2,500-kilometre corridor simultaneously.

Counter-parallel: Operation Earnest Will succeeded because the threat was to individual vessels from mines and missiles, allowing convoy protection. There is no analogous response to a denial zone that degrades navigation infrastructure across two entire sea lanes.

The Cape of Good Hope detour adds 10 to 14 days and $500,000 to $1 million per voyage. Combined GNSS denial and the physical threat at both chokepoints effectively makes the Cape route the only commercially viable option for most carriers.

Insurance costs for Gulf and Red Sea transits have already risen sharply. The combined GNSS denial zone eliminates the risk-reduction argument that the Red Sea is a safer alternative to Hormuz.

Consensus view: RUSI maritime security researchers and Lloyd's List Intelligence assess the GNSS denial corridor as a layered access denial strategy: degrading navigation instrumentation reduces both commercial willingness to transit and the tactical effectiveness of any anti-IRGC naval operation.

Counter-view: The Turkish maritime authority UDHB and Chinese COSCO maritime risk analysts note that modern vessels carry inertial navigation backups and that the denial zone, while severe, does not render transit physically impossible — it increases risk and insurance cost rather than creating a hard barrier.

Key tension: Whether the GNSS denial zone is a direct precursor to kinetic action against vessels attempting the Red Sea detour, or a sustained electronic deterrent intended to raise costs without triggering a new military confrontation.

Sources:International Maritime Organisation / UKMTO·International Maritime Organisation / UKMTO·US Maritime Administration

Mentions:Strait of Hormuz →Pakistan →Iran →Bab al-Mandeb →Islamic Revolutionary Guard Corps (IRGC) →Houthis →UKMTO →

First Reported In

Update #51 · Iran hits aluminium plants; Hormuz emptying

International Maritime Organisation / UKMTO· 29 Mar 2026

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Causes and effects

Caused by

Houthis threaten to close Bab al-Mandeb

The GNSS denial zone extending to Bab al-Mandeb is the electronic precursor to the physical closure threatened by Houthi minister Mansour.

Occurred 28 Mar 2026

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This Event

GPS blacked out across Gulf chokepoints

The deliberate GNSS denial zone eliminates the Red Sea as an alternative to Hormuz, trapping commercial shipping between two contested chokepoints with degraded navigation systems.

Led to

Houthis threaten second chokepoint

GNSS denial across both chokepoints supports the coordinated Houthi-Iran electronic warfare enabling the sustained missile campaign against Israel.

Occurred 30 Mar 2026

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Different Perspectives

US money managers (CFTC-tracked)

US money managers had trimmed WTI net long positioning into July's rally, doubting the Hormuz premium would hold without freight or war-risk confirmation, and the crude stock build reported for the week to 17 July gives that scepticism a fundamentals basis. The 25 July CFTC data will show whether Brent's move above $100 changed their calculus.

Asian distillate buyers (Singapore)

Singapore's distillate holders kept retaining middle-distillate barrels as the East-West arbitrage window narrowed further this week, a pattern that sharpened as Fujairah light distillates hit a record low. Cargoes are being held rather than released west into the tightening Mediterranean market.

Bulgaria

Bulgaria secured the removal of Lukoil founder Vagit Alekperov and Patriarch Kirill from the 21st package, with President Rumen Radev calling a personal listing 'shooting ourselves in the foot'. Sofia is protecting its position in Lukoil's EUR 3bn compensation claim over the 2023 Neftohim Burgas nationalisation.

Russia

Russia loses the roughly $14 a barrel of legal headroom the price-cap formula would have released toward $58, even as Urals continues trading below Moscow's $59 budget floor. The shadow-fleet insurance workaround that lets sanctioned crude clear above $44 in practice remains untouched by the freeze itself.

European Union

The EU adopted its 21st sanctions package on 23 July, freezing the $44 Russia oil cap for 12 months rather than letting the formula drift it toward $58, and listed shadow-fleet support vessels for the first time. The package cleared only after three failed Coreper votes.

Marine war-risk underwriters (Lloyd's-linked syndicates)

War-risk syndicates lifted southern Red Sea hull premiums 150% to about 0.75% of hull value after the 20 July blockade declaration, still a seventh of the roughly 5% Hormuz band. Underwriters reset on realised loss, not declared threat, so the 23 July Encelia and Layla strikes set up the next re-mark.