For any operator moving tonnage through the Gulf of Oman, the Arabian Gulf or the southern Red Sea, the long-running confrontation between Iran and Israel is not a distant geopolitical story. It is a direct and recurring threat to crews, hulls and schedules. For more than a decade the two states have fought a covert campaign at sea, striking each other's commercial and commercially linked shipping through limpet mines, drones, missiles and electronic interference. The killing of two civilian mariners aboard the tanker Mercer Street in July 2021 showed how quickly that quiet campaign can spill into lethal, headline-grabbing violence. Understanding the pattern, and where it is most likely to touch your vessel, is now part of routine voyage planning.
What the shadow war is
The phrase "shadow war" describes a sustained, largely deniable conflict conducted below the threshold of open state-on-state warfare. Rather than declaring hostilities, Iran and Israel target each other's interests through proxies, sabotage and covert action. At sea, this has meant attacks on tankers and cargo vessels with a real or perceived link to the opposing side: Israeli-owned or Israeli-operated ships, vessels carrying Iranian oil, and the commercial partners of both.
The campaign is attritional and episodic. A strike is followed by weeks of calm, then a reprisal, then a further escalation. Neither side routinely claims responsibility, which leaves shipowners, insurers and flag states to attribute incidents from forensic evidence and pattern analysis rather than open admissions. That ambiguity is deliberate. It lets each state apply pressure while retaining the option to deny involvement and avoid a wider war.
Why it matters to maritime operators
The central problem for commercial shipping is that the conflict is fought through merchant vessels, not navies. A tanker chartered for an ordinary voyage can become a target because of its registered owner, its operator, its recent port calls or simply its appearance on a watchlist held by one side or the other. Crews who have no stake in the dispute carry the risk.
The Mercer Street attack made this explicit. On 29 July 2021 the Panama-flagged, Japanese-owned and Israeli-managed product tanker was struck off the coast of Oman in the Arabian Sea. Two crew members died: the Romanian master and a British member of the onboard security team. Dryad Global analysts assessed at the time that the loss of civilian life meant the confrontation could no longer reasonably be described as limited or as a shadow war. It had crossed into open, attributable violence against civilian seafarers.
For operators, three consequences follow:
- Geography of risk. The threat concentrates around the chokepoints that connect Gulf oil to world markets: the Strait of Hormuz, the Gulf of Oman and the wider Arabian Sea, and the southern Red Sea and Bab-el-Mandeb where Iran-aligned groups operate.
- Ownership exposure. Beneficial ownership, management and charter relationships shape whether a vessel is likely to be selected. A clean cargo does not remove the risk if the corporate chain links to a flagged interest.
- Commercial cost. Heightened threat levels drive war-risk insurance premiums, additional security measures and, in acute phases, rerouting that adds days and fuel to a voyage.
The methods in play
The shadow war has been waged with a recognisable toolkit, and operators should understand each method because the warning signs and mitigations differ.
| Method | What it looks like | Operator concern |
|---|---|---|
| Limpet mines | Explosive devices attached to a hull at or below the waterline, often while a vessel is at anchor or slow-steaming | Vulnerability during anchorage and reduced-speed transits; need for hull watch and waterline checks |
| Drones and loitering munitions | One-way attack drones flown into the superstructure or hull | Limited warning time; accommodation and bridge are the likely impact points |
| Missiles and projectiles | Stand-off strikes launched from shore or fast craft | Difficult to defend against commercially; reinforces the case for routing away from threat arcs |
| Seizure and boarding | Diversion of vessels by fast boats or helicopter-borne teams, sometimes under the guise of an inspection | Loss of vessel control, detention of crew, prolonged commercial disruption |
| Electronic interference | Jamming and spoofing of satellite positioning, falsifying a vessel's reported position | Navigational uncertainty near sensitive waters; risk of being lured or pushed into a claimed jurisdiction |
Global Positioning System spoofing deserves particular attention. By broadcasting false signals, an actor can make a ship's bridge believe it is somewhere it is not, a tactic that has been used to complicate transits near the Strait of Hormuz. A master acting on a spoofed position may unknowingly stray toward contested waters or present an easier target. Independent position cross-checks, using radar, visual fixes and shore references, are a practical countermeasure.
What it means for your passage plan
The shadow war is not a constant-intensity threat. It surges after each major incident and ebbs in between, which makes current, well-sourced situational awareness more valuable than a static risk rating. A route that was acceptable last quarter may sit inside a sharply elevated threat arc this week following a single strike or a political flashpoint.
Sound practice for vessels transiting the Gulf of Oman, the Strait of Hormuz and the southern Red Sea includes:
- Building a vessel-specific threat picture that accounts for ownership, management and charterer, not just cargo and flag.
- Hardening against drone and limpet-mine attack: bridge and accommodation protection, anchorage hull watches, and waterline inspections before and after slow-speed or anchored periods.
- Treating positioning data as potentially compromised near chokepoints and maintaining independent navigational fixes.
- Reviewing routing and timing against the latest assessed threat, and retaining the flexibility to delay, reroute or transit in convoy when intensity spikes.
- Keeping war-risk cover, security arrangements and reporting procedures current and rehearsed.
The thread running through all of this is information. The difference between a routine transit and an exposed one is whether the operator knows, in time, that the threat has moved.
Where Verihelm helps
Turning a fast-moving, deniable conflict into decisions a master can act on is exactly the problem Verihelm is built to solve. The platform ingests the raw signals of incidents at sea, then puts them through analyst verification so operators receive assessed intelligence rather than unconfirmed chatter. For the Iran-Israel shadow war that means attributing attacks against the established pattern, tracking how threat arcs shift around Hormuz, the Gulf of Oman and the Bab-el-Mandeb, and flagging when a vessel's ownership or routing places it in the line of fire. Operators see the change in posture early enough to alter a passage plan, brief a crew or adjust insurance, instead of learning of it from a casualty report. For the wider context behind these assessments, explore Dryad Global's regional and threat intelligence coverage.