North Korea Says It Has Underwater Missile Silos, but Experts Aren’t So Sure

On Monday, North Korean state media noted the use of an underwater missile silo—the first mention of such a facility. It was used Sept. 25 as soldiers practiced the loading of tactical nuclear warheads under a reservoir in the country’s northwest, the state-media report said.

State-media photographs showed a missile roaring out of the water, the rocket’s glow barely visible behind the cascading waves and plumes of smoke. The launchpad wasn’t visible. North Korea didn’t release video footage.

The launch was likely conducted from a submersible barge that is mobile, rather than a cavernous structure with a fixed location that is built beneath the water, weapons experts say.

Constructing an underwater missile silo poses a series of logistical hurdles, said

Bruce Bennett,

a North Korean weapons expert at Rand Corp., a policy think tank. Building it, he added, would likely require digging under the reservoir itself.

The missile silo could be filled with air or water, though sealing off the space would still run the risk of leaks that could lead to corrosion, Mr. Bennett said. Keeping the missile—and a nuclear warhead—inside the silo would probably require a continuous security presence nearby, which could arouse suspicion from the U.S. and its allies who monitor the North with sophisticated satellite imagery. Not storing the missile there means having to move it to the launch site in a time-consuming process that is difficult to cloak, he said.

“Building a true underwater silo would be far more difficult and costly, and the effort would have a significant footprint,” Mr. Bennett said.

The purported underwater-silo launch was one of seven North Korean missile tests in recent weeks that state media chronicled on Monday, a holiday celebrating the founding of the country’s ruling Workers’ Party. The tests were part of drills simulating tactical nuclear strikes against the U.S. and South Korea and guided by Kim Jong Un, state media said.

By publicly discussing underwater silos, the U.S. and South Korea are now put in a position to assess whether the Kim regime’s claims are feasible, and if so, committing further resources to search for the missile facilities, said

David Maxwell,

a senior fellow at the Foundation for Defense of Democracies, a Washington think tank.

“Something else the regime may be doing is trying to make us think they have silos when in actuality they are talking about the submerged barge” used for other launches in recent years, said Mr. Maxwell, a retired U.S. Army Special Forces colonel, with extensive experience in Asia.

The potential for North Korean underwater silos adds another layer of mystery to the Kim regime’s weapons program. Pyongyang has around 20 undeclared missile bases, according to an assessment by the Center for Strategic and International Studies, a think tank in Washington. That includes a secret missile base in its Chagang province bordering China, where North Korea last week launched the intermediate-range missile that flew over Japan in a major provocation.

This year, North Korea has test fired missiles from different locations, including trains, in an effort to make it more difficult for Washington and Seoul to detect and destroy potential launches. But it is rare for countries to launch missiles from an inland body of water, military experts say.

Still, it is likely that Washington and Seoul’s current missile defense systems aren’t able to fully detect and strike every type of North Korean missile, especially ones that travel at low altitudes or come from unexpected places, said

Cho Dong-youn,

a former South Korean army major and a military-studies professor at Seo Kyeong University in Seoul.

The initial assessments for the Sept. 25 test from Seoul’s military didn’t specify that the missile had been fired from an underwater launch site, instead believing it had come from a land-based transporter erector launcher.

“North Korea is not only expanding its arsenal but also changing its military strategy, to find holes in the allies’ defense systems,” Ms. Cho said.

On Tuesday, South Korean President

Yoon Suk-yeol,

a conservative who took office in May, said North Korea’s advances threaten the world and that there is nothing to be gained by the rogue country from nuclear weapons.

Under Mr. Yoon, South Korea has emphasized a so-called Kill Chain system to counter North Korean threats. Developed a decade ago, the Kill Chain calls for pre-emptive strikes against North Korea’s missiles and even its leadership if an attack is detected. The Yoon administration announced a Strategic Command will be created by 2024 to oversee pre-emptive-strike strategies.

Mr. Yoon has also called for bolstering counterforces by expanding South Korea’s weaponry including ballistic missiles, stealth fighters and submarines. Seoul is also seeking to develop its own satellites to detect North Korean targets independent from the U.S.

The Kim regime’s underwater silos represent a “last resort method” against South Korea’s Kill Chain system, a spokesman for Seoul’s defense ministry said Tuesday.

Write to Timothy W. Martin at [email protected] and Dasl Yoon at [email protected]