US Pre-empts Iranian Rocket Deployment of Sea Mines in Strait of Hormuz

An Iranian Fajr-5 with sea mine payload being launched during Exercise Great Prophet-19 in January 2025 (DEFA Press.IR)

In the first US attack mounted on Iran for about a month, US Central Command (CENTCOM) fired on IRGC positions on Larak Island late on August 30. The move was to intercept and destroy two Iranian missiles that were about to be launched.

Although statements from Washington suggested a broader attack had been carried out on other targets, the CENTCOM operation appears to have been very precise and limited to preempting an Iranian attack, which was imminent. The Iranian response appears to have been scaled to reflect the limited nature of the U.S. action.

Although CENTCOM did not issue details, the target for the attack appears to have been one or more IRGC Fajr-5 rocket systems, which can be used to deploy sea mines. The Maritime Executive covered Exercise Great Prophet-19 which took place in January 18-23 in 2025, during which Fajr-5 rockets, each with a single sea mine on board, were launched from positions along the Strait of Hormuz coast from track mounted launchers. The Fajr-5, a 333mm caliber Multiple Launch Rocket System, is usually equipped with a conventional high explosive warhead, and since its introduction in the 1990s has been widely exported within the Axis of Resistance, a particular favorite of Hezbollah in Lebanon.

The Fajr-5 rocket is launched from a mobile truck-mounted launcher with four rocket tubes, suggesting that the IRGC were attempting to send eight mines into the Strait of Hormuz, presumably targeting the Omani Channel on the southern side of the Strait. Mines deployed by this system are free-floating, drifting mines, with a relatively small explosive charge and unlikely to be tethered. To withstand the flight stresses, the fusing system of the sea mines is likely to be quite insensitive.

When Donald Trump announced that the mines had been cleared from the Strait, he wrote online, "Iran has been notified that any ship or boat placing new mines will be immediately and systematically destroyed. There is a Zero Tolerance policy on mine placement in full force and effect."

This is an inefficient and complex method of laying mines, and reflects something of an emergency situation for the IRGC – for whom it may now be difficult to lay mines from speed boats as they have been wont to do before. Use of the Fajr-5 deployment system also gives credence to Central Command claims to have cleared mines from the Strait, suggesting that the Iranians are seeking to reverse this mine clearance and improve their control of ship movements in the Strait. In this context, the Iranian claim to control the Strait is looking increasingly threadbare.