On the last day of 2020 a Greek oil tanker at anchor off Iraq was found to have an Iranian limpet mine attached. The mine was apparently attached to the hull by a diver dropped off at night from one of the armed Iranian speedboats that move through the area at all hours. Another Iranian speedboat then came along and picked up the diver. Iran has been using these tactics since 2019 when they were caught using limpet mines and other weapons against tankers entering the Persian Gulf. In one case the Iranians were caught on a video placing and removing the limpet mines on tanker hulls. In mid-2019 the U.S. provided surveillance video of Iranians in a small boat removing a limpet mine that did not go off. The video was taken by an American MH-60R surveillance helicopter patrolling the Gulf of Oman when a small boat was spotted, apparently Iranian and headed towards an anchored tanker. The helicopter stayed with the small boat and eventually got the video of the Iranians removing a limpet mine. At one point an Iranian spotted, or suspected, the distant helicopter overhead and fired a portable anti-aircraft missile at it, which missed. MH-60Rs are equipped to deal with such missiles.
These mines use magnets to remain on the hull and are detonated by timer or remote control. Iran denies they are using these mines but the video and past performance say otherwise. Iran often stages attacks on shipping using naval mines or remotely controlled speedboats loaded with explosives, Iran does this because they can deny responsibility and avoid triggering a destructive response.
The late 2020 another limpet mine was discovered by the security contractors on the ship. An Iraqi EOD (Explosives Ordnance Disposal) team was brought in and within 24 hours the mine was disabled and removed. Apparently, this prompt action in detecting and deactivating the mine prevented Iran from carrying out another anonymous attack on shipping in the Persian Gulf and Red Sea. The disabled mine was scrutinized to determine where it came from. Iran does manufacture limpet mines, something that was made public in 2015 when a navy media event displayed the many naval weapons manufactured in Iran. One of these was a 42 kg (92 pound) limpet mine, described by Iranian media as a “sticking mine.” Another Iranian news item in 2020 showed naval personnel carrying out a variety of chores, including placing a limpet mine on the hull of a ship. Iran has apparently manufactured smaller, and lighter, limpet mines that can be more easily transported and emplaced by speedboat crews or divers using underwater flotation devices to carry the limpet mines. The flotation devices are uninflated after use and taken away by the divers.
So far, all these Persian Gulf, Red Sea and Gulf of Oman incidents have been traced back to Iran, which denies any involvement. This sort of “it wasn’t me” terrorism is a favorite tactic of Iran and it keeps getting used because the Iranians know how to back off (stop the mining) if the public outroar becomes too intense. Once the outrage has passed from the headlines, Iran will resume the unattributable attacks. Over the last decade several investigation teams, including one from the UN, have examined the evidence and concluded that Iran was the source of the weapons. Iran has tried to make that more difficult by using unmarked components. This does not work because the source of such parts can, and has been, traced back to Iran.
Iran does make some threats openly, but usually the kind that sound scary but Iran rarely follows through. For example, after the Americans revived their sanctions in 2017, Iran threatened to close the Straits of Hormuz or, at the very least, assert control over the Straits. Iran sometimes runs into problems while publicizing such threats. For example, by early 2018 the United States had moved military forces into the Gulf region to deal with any Iranian efforts to close the Straits. This effort gained added impact because even China is opposed to Iranian threats to close the straits. The U.S. also noted that its current military posture in the Gulf had put an end to Iranian harassment of U.S. warships. There had been 22 of those incidents in 2015, 36 in 2016 but only 14 in 2017, none in 2018 and in 2019 there have been attacks (as with the limpet mines) against tankers but nothing Iran will take credit for.
In 2019 the Iranian use of limpet mines and other weapons against tankers entering the Persian Gulf has led to a sharp increase in demand for the armed guards normally employed by large ships passing close to pirate-infested Somali waters. As a result of this some Iranians were caught on camera placing and removing limpet mines to the sides of tankers. These mines use magnets to remain on the hull and are detonated by a timer or remote control. The armed guards hired were there to scan for such mines, to stand watch at night and fire on any small boats that approach a tanker at night. Iran has plenty of experienced “combat divers” who practice moving underwater at night over long distances to carry out surveillance or something like putting limpet mines on ships while not being detected. Even getting caught in the act once or twice is not enough to trigger major retaliation. One or two incidents can be explained with the “rogue element” excuse. Eventually the weight of evidence triggers serious retaliation and that’s when Iran backs off for a while.
Israeli intelligence agreed with the Americans, who captured Iranians on video, that Iranian IRGC (Islamic Republican Guard Corps) operatives have used limpet mines to anonymously attack shipping near the Straits of Hormuz. Warships tend to be more alert to such threats but there are far more commercial ships (mainly tankers) moving through the Gulf of Oman and past Hormuz and into the Persian Gulf to pick up oil cargoes. Many of these tankers will sometimes anchor just off the shipping channel overnight, or longer, waiting for an available berth. Crews on these huge (often size of a large aircraft carrier) ships are small, usually fewer than 40 personnel, and except for someone on the bridge to answer the phone and monitor the automated systems that run the engines and so on, there is no one watching out for small boats approaching in the darkness and quietly attaching or removing a limpet mine. In mid-2019 two tankers in the Gulf of Oman were apparently attacked with limpet mines that did explode and caused fires.
The Iranians were angry at the American response to their tactics. Evidence of Iranian responsibility for “it wasn’t me” terror operations were part of the evidence the Americans presented to justify reviving sanctions on Iran. This did major damage to Iranian terrorist activities. Then, in early 2020, the Americans used a UAV missile attack to kill Qasem Soleimani, the veteran commander of the IRGC Quds Force. Quds specializes in overt and covert terrorism outside Iran and the loss of the charismatic and very effective Quds boss was a major setback and embarrassment. Iranian limpet mines remain in play, even though this has led to more evidence of Iranian bad behavior.