July 19, 2021: Iran is once again making a major effort to covertly use naval mines against its enemies. In this case the victims are everyone who uses the Suez Canal and sends ships anywhere near the Yemen coast. While these are Iranian mines, a proxy (Iran-backed Yemeni Shia rebels) takes credit for placing the mines in the water. Hundreds of these mines have been placed off the Yemen Red Sea and Arabian Sea coast in the last few years but the damage has been minor. No ships have been sunk, despite the fact that a small percentage of the mines were more modern and deadly bottom mines that rest on the ocean floor in shallow water (no more than 60 meters/190 feet deep) and use pressure sensors to detect a target and detonate. The Iranian bottom mines seen off Yemen so far are not the most modern design and suitable only for shallower (20 meters) coastal waters. Perhaps the less-effective mines were used on purpose, to disrupt shipping, but not sink a lot of it because that might create a major international uproar and calls for international military action against Iran.

Iran has long insisted that because of its naval mines they would have no trouble blocking the export of oil via the Straits of Hormuz. About a third of the world's oil shipments pass through these straits, which comes to about 15-20 tankers a day, plus a dozen or more non-tankers. The Persian Gulf, in general, is a busy waterway. It is 989 kilometers long and the average depth is 50 meters with maximum a depth of 90 meters. Naval mines are Iran's best bet if they want to shut down the straits. Their problem is that they have a small navy, an obsolete air force, and a poor track record when it comes to shutting down tanker traffic in the Persian Gulf or the Straits of Hormuz. They tried once before, in the 1980s, when they were at war with Iraq. The two antagonists began attacking each other's tanker traffic early on, in an attempt to cut off each other's oil sales and their military purchases. Iran didn't want to shut the Straits of Hormuz because it needed the oil revenue more than Iraq, which was getting billions in loans and aid from other Arab states. Both nations concentrated on attacking shipping in the Persian Gulf. Over 500 ships were attacked, 61 percent of them tankers. Only 23 percent of the tankers attacked, mainly with anti-ship missiles, were sunk or immobilized. Attacks by fighter-bombers and warships only hit about two percent of Gulf’s ship traffic Gulf. Iran lowered its oil prices to cover the higher cost of ship insurance and, in 1986, Russia and the United States intervened to protect Kuwaiti and Iraqi tankers, which were taking most of the damage.

The Iranian military is in worse shape today than it was in the 1980s and would not last long trying to attack ships. That leaves the Straits of Hormuz. This is actually a wide (about 30 kilometers) deep channel. Normally, shipping sticks to narrow (a few kilometers wide) channels, going in and out, to avoid collisions. The main Iranian threat has always been seen as naval mines. The Arab states have a lot of mine clearing equipment and more numerous air and naval forces than Iran. In addition, there are the United States and NATO forces in the area. The problem was that all these mine clearing forces had never practiced under realistic (wartime) conditions. In short, it has long been unclear exactly what it would take to deal with Iranian mines in the straits. Some of those questions were answered after 2012 as Arab and NATO nations held numerous joint mine clearing exercises in the Gulf. This enabled each nation to demonstrate what they had and use in conjunction with other nations to see how long it would take to clear some of the most modern naval mines. These exercises revealed a lot of flaws in equipment design and user mishandling. That’s one of the primary goals of the joint exercises and it shows the manufacturers of this equipment what needs to be fixed or improved.

For an Iranian mining attempt to work they would have to get the mines onto the bottom of the straits and then prevent the rest of the world from clearing those mines. That would be difficult, as would Iranian attempts to plant additional mines. Such attempts would not be impossible as Iran has small submarines and speed boats along with sailors willing to carry out suicidal missions to deliver the mines. Even that may not be sufficient, as this sort of fanaticism failed against the Americans in the 1980s. While Iran has worked to overcome their shortcomings, most of the solutions appear to be publicity stunts mainly meant to make the Iranian population feel better.

Iran has a few thousand naval mines and that is a small arsenal compared to Russia (over 200,000), China (over 100,000) and North Korea (over 50,000). Most of the Iranian mines are the older moored (floating) mines. They have some bottom mines and claim to have copied modern Russian and Chinese designs. Russia would not mind Iran having modern bottom mines because using them to block the entrance to Persian Gulf would disrupt oil shipments long enough to sharply increase the price Russia could get for its oil. China is a major oil importer and would suffer if Persian Gulf access were blocked.

It is generally agreed that all these mines are a serious danger. While often ignored, naval mines are a formidable weapon. But these passive weapons just don't get any respect. The historical record indicates otherwise.

The current naval mine threat off Yemen is a recognized danger to all ships and in early 2020 shipping companies warned their ship captains that many more naval mines, of the contact type, were floating into the Red Sea from the north Yemen coast. That coast is off the Shia rebel home province of Sadaa and the rebels had been releasing a few of these mines periodically for years in an effort to disrupt Red Sea shipping traffic to and from Saudi Arabia. The currents generally flow north in this part of the Red Sea, towards the major Saudi Red Sea port and the entrance to the Suez Canal. The floating contact mines are a 19th century development that has been improved on for over a century and is still used because it is cheap and effective. Iran has provided the Shia rebels with these mines which are normally kept in place by a cable or chain between the mine and an anchor on the sea bottom. The Shia rebels cut the cable and let the mines drift into the Red Sea. American warships are part of the international naval blockade of Yemen, to prevent smuggling and to deal with the mines, which are a danger to the warships as well as commercial shipping. During 2020 there was a major effort to locate and neutralize these free-floating mines. By the end of 2020 over 160 mines were found and neutralized. The rebels continued putting mines in the water during 2021 and the number found and neutralized remained at 2020 levels. The Shia rebels continue putting these mines in the water and claim self-defense against oppression by the Yemeni government and their Arab nations helping them.

Ever since the end of the Cold War a growing number of American naval officers and civilian experts have been urging that more attention be paid to dealing with naval mines. The United States was not alone and in 2012 that led to the U.S. and over 30 other nations conducting a joint mine clearing exercise, called the International Mine Countermeasures Exercise 2012. The numerous training events were directed at dealing with Iranian attempts to block the entrance (Straits of Hormuz) to the Persian Gulf. The impact of that exercise led to another being held annually ever since. While Iran is the most immediate user of naval mines, it is not alone. North Korea, China and Russia have much larger naval mine stockpiles, but these three are not boasting of how and when they would use them.

Modern naval mines were widely used for the first time over a century ago, during the Russo-Japanese war (1904- 1905). These were contact mines, floating in shallow water and kept in place with an anchor and chain. When the tide was right, they would be just below the surface, ready to explode whenever struck by a ship. Some 2,000 of these mines were used to destroy sixteen ships during the Russo-Japanese war. That's one ship lost for every 125 mines used.

During World War I (1914-18), modern mine tactics and clearing methods evolved. Thousands of mines were laid to provide defensive barriers against enemy movement in the North Sea. Mines were also used offensively by secretly placing them across known enemy sea routes. More than 1,000 merchant and war ships were lost because of the 230,000 mines used. That's over 200 mines used for every ship lost.

During World War II a total of 2,665 ships were lost or damaged to 100,000 offensive mines. That's one ship for every 37 mines. Some 208,000 mines were used defensively to inhibit enemy movement and tie up his resources.

Naval mines achieved several striking successes during World War II. In the Pacific naval mines proved more destructive to the Japanese war effort than the atom bombs. During a 10-week period between April and August 1945, 12,000 mines were dropped along the Japanese coast by American bombers. These destroyed 1,250,000 tons of Japanese shipping (670 ships hit, 431 destroyed). That's 18 mines for each ship hit. The Americans had air superiority, so losses during these 1,500 missions amounted to only 15 planes, most of them accidents. Had these missions been flown against opposition, losses would have been between 30 and 60 aircraft, plus similar losses to their fighter escorts. Either way it was a stunning success for naval mines,

A conventional submarine campaign was also waged against Japanese shipping using mines. Comparisons between subs using mines and torpedoes are interesting. A hundred submarines were involved in a campaign that ran for 45 months from December, 1941 to August, 1945. Some 80 percent of the pre-war Japanese merchant fleet was lost. That’s 4.8 million tons of enemy shipping was sunk with torpedoes. For every US submarine sailor lost using submarine launched torpedoes, 560 tons of enemy ships were sunk. During the mine campaign 3,500 tons were sunk for each U.S. fatality. On a cost basis the difference was equally stark. Counting the cost of lost mine laying aircraft (B- 29's at $500,000 each) or torpedo armed submarine ($5 million each), we find that each ton of sunk shipping cost six dollars when using mines and fifty-five dollars when using submarines. This data was classified as secret until the 1970s. It indicates that mines might have been more effective than torpedoes, even if the mines were delivered by submarine.

The Germans waged a minelaying campaign off the east coast of the United States between 1942 and 1944. Only 317 mines were used, which sank or damaged 11 ships. This was a ratio of 29 mines used for each ship hit. More importantly eight major ports were closed for a total of 40 days. One port, Charleston, South Carolina, was closed for 16 days, tying up not only merchant shipping but the thousands of men, warships, and aircraft dealing with the situation. American submarines also waged a limited mine campaign in the Pacific. For 658 mines used, 54 ships were sunk or damaged (12 mines per ship). No subs were lost. Considerable Japanese resources were tied up dealing with the mines. The Japanese-held Palau atoll’s port was closed by submarine delivered mines and not reopened until the war ended. Even surface ships were used to lay mines. Three thousand mines were laid by destroyers. Only 12 ships were hit but these were barrier fields, not the ambush type mine fields that a submarine can create by sneaking into an enemy held area.

In Korea during the early 1950s, the Soviets provided North Korea with 3,000 mines, many of 1904 vintage. These were used to defend Wonson harbor. It took several weeks for UN forces to clear these, at a loss of a dozen ships hit. Half of these ships were destroyed.

During the Vietnam War over 300,000 American naval mines were used, primarily in rivers. The vast majority were not built as mines but were aerial bombs equipped with magnetic sensors instead of fuzes so they could operate like bottom mines. These bombs/mines used a small parachute to ensure that no damage occurred on landing. In shallow water these makeshift weapons sat on the bottom and performed as well as mines. Haiphong Harbor was actually mined with 11,000 of these "destructors," as the US air force called them, and less than a hundred conventional mines. Haiphong Harbor was shut down completely for months, and it took years to clear out all the American mines. The "destructor" mine design was so successful that it is still in use, using more modern electronics, as the Mk 62 mine.

During the 1991 Gulf War the Iraqis laid over a thousand mines off the Iraqi and Kuwaiti coast. The predominantly US naval forces did not have sufficient mine sweeping resources to deal with this situation and had a helicopter carrier and cruiser hit and damaged while trying to clear the area. This effectively prevented any US amphibious operations, although the Marines were not going to be used for a landing anyway. It took over a month of mine clearing after the fighting ceased to eliminate all the mines. In the meantime, two U.S. warships were damaged by these mines. In 2003, the Iraqis again tried to use mines, but were hampered by prompt American, British, and Kuwaiti action.

In any future war naval mines will again surprise everyone with how effective they are. It is feared that terrorists might get their hands on some bottom mines, but so far, there do not appear to have been any attempts.

Meanwhile the 2012 international mine clearing exercise prompted the United States to make several moves to improve mine clearing capability. The U.S. Navy ordered several dozen more of the expendable SeaFox UUVs (unmanned underwater vehicles). These are used to destroy bottom mines. These UUVs were sent to the Persian Gulf to deal with potential Iranian use of naval miles. The Seafox UUVs are used on Avenger mine hunting ships already in the Persian Gulf.

SeaFox is a small (1.4x.4x.2 meters/55x16x8 inches) battery powered sub that weighs 43 kg (95 pounds) and has a fiber-optic cable connecting it to a surface ship or hovering helicopter. There the controller can move the SeaFox close to a suspected mine (using a small sonar unit to assist navigation), then turn on a spotlight for a vidcam to examine the object and determine if it is a mine. If it is, SeaFox gets closer and detonates a shaped charge explosive, sending a shaft of hot plasma through the mine destroying itself and the mine. SeaFox has an endurance of about 100 minutes, a top speed of 10 kilometers an hour, and can dive as deep as 300 meters (930 feet).

The only American minesweeper ships are the 13 Avengers which are getting old and only eight of the original 14 remain in service. The U.S. Navy does not plan to replace them.

The U.S. Navy kept these elderly (entered service between 1987 and 1994) Avengers in service because replacements (minesweeping helicopters and minesweeping versions of the new LCS ship) have been delayed by technical problems. Meanwhile, the U.S. upgraded the sonars on its Avenger class ships. The new mine hunting sonar improves the ability of the sonar to spot mines on sea bottoms cluttered with other stuff (natural or manmade). In many parts of the world shallow coastal waters are used as a dumping ground for junk that won’t float ashore. This has been found to help hide bottom mines. The Avengers have also received new engines. The four original diesel engines in each Avenger have never been very reliable. Upgrades to the Avengers were meant to keep them in service until 2020 and now they will remain operational for as long as possible.

The upgrade is part of an attempt to deal with delays in the arrival of the LCS class ships, or at least the ones equipped for mine hunting. The LCS was a failure and the navy is starting to retire some of them early.

The navy has also equipped helicopters for mine clearing. But the navy is having a very difficult time maintaining its force of 30 MH-53E helicopters. These aircraft are the only ones that can tow a sled containing naval mine detecting gear. This sort of thing is called AMCM (Airborne Mine Countermeasures) and is considered essential in areas, like the Persian Gulf, where the enemy (Iran) might use a lot of naval mines that would have to be cleared quickly in wartime. SeaFox has been upgraded.

The U.S. Navy also developed a complementary system, ALMDS (Airborne Laser Mine Detection System). Designed to operate from the MH-60S helicopter, ALMDS uses a Laser Imaging Detection and Ranging blue-green laser to detect, and identify naval mines near the surface. Unlike the AQS-24A, ALMDS operates from the low flying, and smaller, helicopters. Surface mines are either moored (via a chain to the bottom) or floating (a favorite terrorist tactic), and many float just below the surface. The laser works very quickly, and enables the ALMDS equipped helicopter to quickly check out large areas for surface mines. Terrorists have used naval mines before, of the floating variety. Navies tend to use the more sophisticated, expensive and hard-to-get bottom mines (that lie on the bottom, in shallow water).

American allies have also developed new mine detection and clearing tools and some of the new U.S. equipment uses foreign tech. While new mine designs have become more effective, the basic problem is that the many older mine designs are still very dangerous, especially for the unprepared. Israel, which faces a more immediate threat from naval mines than anyone else, has developed several novel systems that make use of USV (unmanned surface vessels) and submersible systems similar to SeaFox.

The United States continues to participate in international mine clearing exercises with its NATO allies as well as in the Persian Gulf. There the effectiveness of the systems available, but the United States does not own, are regularly demonstrated.