What Happens to Iran’s Sea Mines After War?

As the United States and China race to dominate advanced technologies such as artificial intelligence and semiconductors, Iran leaned on an age-old instrument to bring the world economy to its knees: sea mines. A cease-fire between Washington and Tehran appeared to buckle on Wednesday, putting plans to fully reopen the Strait of Hormuz in jeopardy. It is unclear how much of the critical shipping route Iran mined during the recent war—and how long it will take for commercial ships to be certain that the waterway is clear.

This has implications beyond Iran. Sea mines are relatively old and simple technology. But controlling their spread and use may be just as important as doing so for technologically advanced weaponry. Both China and the United States have skin in the game.

Iran’s blockade of the Strait of Hormuz had little historical precedent. Starting in late February, Tehran effectively blocked 20 percent of the world’s oil (and nearly half of China’s oil supply) for months, stranding around 2,000 ships in the Persian Gulf. Iran’s Islamic Revolutionary Guard Corps warned in April that that there was a “likelihood of the presence of various types of anti-ship mines in the main traffic zone.”

The Hormuz crisis underscored how much both Washington and Beijing depend on free-flowing seas for trade and security. Gas prices spiked to more than $4 per gallon in the United States. With Asian economies cut off from energy supplies, Chinese crude imports fell to their lowest levels in a decade, forcing Chinese firms to draw down their oil reserves.

While the Hormuz crisis shows how acutely sea mines—or even the mere threat thereof—can hurt global trade, they have long posed asymmetric risks.

Sea mines supplied by the Soviet Union and laid by North Korea stalled U.S. ships from reaching Korea in 1950 during the Korean War. In 1984, sea mines laid in the Red Sea—likely by Libya—damaged at least 17 vessels, including a Soviet-chartered freighter. In the so-called “tanker wars” of the late 1980s, Iran laid mines across the Persian Gulf. As part of that conflict, in 1988, an Iranian mine nearly sunk a U.S. ship. By the 2000s, Iran’s arsenal included naval “mines ten times as powerful as those used in the tanker wars of the 1980s,” according to Caitlin Talmadge, a political scientist at the Massachusetts Institute of Technology.

Policymakers, however, have not paid enough attention to sea mines. While the international community has spilled many words—and sanctions—on Tehran’s cruise missile and drone production, it has done too little to stop Iran, or others, from building sea mine arsenals.

There are a few likely reasons for this. Mines have been part of naval arsenals for centuries; the U.S. Navy has been using some form of sea mines since the Revolutionary War. Many of these mines are less expensive and less complex to manufacture compared with more advanced military technologies. To many policymakers, “sea mines have been thought of as primarily coastal defense,” said Christian Kessler, a former U.S. arms control negotiator.

As a result, mines have not been the focus of international nonproliferation treaties that limit the development or supply of other, newer categories of weapons. There is no equivalent for sea mines to the supplier regimes that limit the exchange of missiles, nuclear material, or chemical weapons. The Ottawa Convention, which bans anti-personnel land mines, does nothing to address sea mines. The Wassenaar Arrangement, a voluntary coordination regime that went into effect in 1996, includes mines as one of many weapons that countries agree to control at a national level, but each country has the discretion to decide what weapons to sell—and to whom.

Observers are uncertain to what extent Iran mined the Strait of Hormuz over the last several months. Insurers do not even know for certain that Iran did mine the channel. As Marsh’s Dylan Mortimer told PBS, “whether there are mines there or not, people think there’s mines there and they will operate accordingly.” That uncertainty by itself has been enough to significantly slow the movement of ships through the strait since the cease-fire.

Even advanced mines are blunt instruments. The New York Times reported in April that, according to U.S. officials, Iran “cannot locate all of the mines it laid in the waterway and lacks the capability to remove them,” hindering attempts to reopen the Strait of Hormuz. If Iran can’t fully control the sea mines it laid, countries that sold Iran mines certainly cannot, either.

The United States must learn from this crisis how to stop the next one. The global economy is too interconnected to allow the Strait of Hormuz—or another waterway—to be closed again.

For one, Washington should take a harder look at military technologies that can block key economic chokepoints. Washington can also work with Beijing and other capitals to build a sea mine technology control regime. A National Research Council study recommended such a regime among U.S. allies in 2001, arguing that the United States should “initiate international discussions among U.S. allies and other nonhostile nations to institute a mine technology control regime, analogous to the Missile Technology Control Regime instituted in 1987, to help slow the spread of increasingly sophisticated and threatening sea mines.” A broader coalition including China would be even better.

In recent years, China has been expanding its undersea capabilities and supply chains. Beijing “has a large, growing, and modernizing capability for naval mines, one that could greatly hinder U.S. operations in any Taiwan scenario,” defense expert Scott Truver wrote in 2012. These capabilities are likely only enhanced by the country’s mine-laying drones. As recently as February, China was in late-stage negotiations to sell supersonic anti-ship missiles to Iran.

The Hormuz crisis may make Beijing receptive to stronger sea mine regulation. While the country weathered the strait’s closure by using its significant oil reserves and leaning on clean energy production, it still served as a warning about China’s potential vulnerability to maritime chokepoints.

Ironically, China may have produced some of Iran’s sea mines. That Chinese mines may have become part of the arsenal that limited the country’s own oil supply reflects how much the weapon can boomerang on suppliers.

Inside the Pentagon reported in 1994 that China had already sold Iran the EM-52 rocket-propelled rising sea mine. The Strauss Center at the University of Texas at Austin found that Iran “maintains a substantial collection of newer, more advanced bottom and rising mines acquired from the Russians, Chinese, and North Koreans.”

Iran has made the most of other arms imports from China, too. In 1996, “the China National Precision Machinery Import-Export Corporation, a state-run enterprise, delivered 60 C-802 model cruise missiles to Iran,” according to a 1997 U.S. House resolution. Iran later reverse-engineered the C-802 as its domestically produced Noor missile, which Iran claims it used to target U.S. destroyers during the 2026 conflict.

There is also some evidence that Iran’s domestic naval mine production may have had Chinese support. The Center for Strategic and International Studies’ Anthony Cordesman noted in 2005 that Iran “has claimed to be making its own nonmagnetic, acoustic, free-floating, and remote-controlled mines, and it has had Chinese assistance in developing the production facilities for such mines.”

China’s vulnerability to sea mines goes beyond its role as the world’s largest exporter. Beijing also operates the world’s largest navy, according to the U.S. Defense Department. And it has relatively weak countermeasures against sea mines, U.S. Navy Cmdr. Victor Duenow wrote in 2022. It imports more oil through the Strait of Hormuz than does any other country. The Iran war added stress to its already flagging economy.

To be sure, there are obstacles to an arms control regime around a cheap and plentiful armament. Some of the toughest include how to handle existing stockpiles of mines; how to prevent countries such as Iran from continuing domestic naval mine manufacturing; and how to get countries such as Russia and North Korea, which produce large amounts of naval mines, on board. These questions are significant, but they should not stop policymakers from trying to find a solution.

One place to start: ratifying the United Nations Convention on the Law of the Sea, which codifies the “right of transit passage” for “straits used for international navigation.” Neither the United States nor Iran is a party to it. In Washington, the treaty has never been able to get past Senate Republicans, who view it as a breach of U.S. sovereignty, despite support from a wide range of stakeholders including the U.S. Chamber of Commerce, the World Wildlife Fund, and ExxonMobil.

The U.N. convention alone would likely not have stopped the Hormuz crisis, even with Iran and the United States as parties. But policymakers in Washington, Beijing, Brussels, and beyond will not be able to reestablish international norms without stronger international frameworks.

Free seas have never been inevitable; they take work to maintain. In an earlier era, the British navy guaranteed them. Over the past century, they have been the product of a U.S.-led world order. The chaos that U.S. President Donald Trump has unleashed across critical economic chokepoints since beginning his second term—from launching a tariff war to bombing Iran—highlights how much the world economy depends on both mutual restraint and careful decision-making by U.S. leaders.

In the wake of the Hormuz crisis and the destruction it wreaked, the world needs a political settlement to formalize that restraint. Something new should come out of all this.