North Korea says it has test-fired two types of submarine-launched strategic cruise missiles off its east coast, in what appears to be the first time its bizarre Hero Kim Kun Ok submarine has been seen at sea in a publicized manner. If the vessel truly was the launch platform, the tests would mark its first confirmed weapons trials and a potential step toward operational service. Unveiled with considerable fanfare in 2023, the Hero Kim Kun Ok has been billed by Pyongyang as a centerpiece of its future nuclear-armed navy, but its operational status and actual capabilities have remained unclear.

The launches took place Wednesday, October 14, with state media Korean Central News Agency (KCNA) reporting the activity earlier today. North Korea said the tests were intended to assess the readiness of its underwater combat systems, improve the Navy’s ability to execute strategic missions, and demonstrate the reliability of its deterrent. Along with imagery of the cruise missiles, KCNA released one photo of the Hero Kim Kun Ok underway, which you can see at the top of this story.

KCNA did not otherwise identify the submarine involved or disclose the missiles’ ranges, flight paths, or performance. South Korea’s Joint Chiefs of Staff (JCS) said it had detected and tracked the launches from before firing through the cruise and terminal phases. A JCS spokesperson said one missile type was launched from a vertical launch system and another from a torpedo tube. This would match the imagery we are seeing, it would also match the Hero Kim Kun Ok’s unique capabilities. The South Korean military assessed that the launches came from a submarine but did not initially identify the vessel publicly.

There remains a possibility that the 3,000-ton-class Hero Kim Kun Ok was not actually involved in launching the missiles. North Korea has long used underwater platforms for test missile launches and has paired these with images of an actual submarine for propaganda purposes. However, the JCS confirming they came from a submarine would lend additional credence to the possibility Hero Kim Kun Ok did indeed launch the missiles. If this is the case, it would indicate that North Korea has begun validating weapons systems aboard the submarine ahead of deployment. At the very least, we can confirm that the Hero Kim Kun Ok is now sailing, although South Korean and U.S. intelligence would be acutely aware of its movements and it could have been in at-sea testing for years now, we just don’t know.

North Korea unveiled the submarine in September 2023, describing it as its first “tactical nuclear attack submarine” and one of the Navy’s core offensive platforms. At the launching ceremony, North Korean leader Kim Jong Un was quoted as saying that arming the Navy with nuclear weapons “brooks no further delay.”

Nevertheless, many questions remain about the submarine’s design and operational prospects. Overall, it remains a heavily modified derivative of a Cold War-era Romeo class diesel-electric submarine — nearly an antique by today’s standards — rather than a purpose-built guided missile submarine. Previous imagery shows 10 missile launch tubes concealed in the prominent ‘turtle back’ aft of the sail, in addition to torpedo tubes, although the precise configuration, usable capacity, and operational status of those systems remain uncertain.

The absence of publicly reported weapons tests from the vessel over the following years raised questions about its development. Analyst Shin Jong-woo of South Korea’s Defense and Security Forum told Reuters that the latest launches suggested combat-system testing for operational deployment was underway. He also suggested that North Korea may have resolved technical problems and could also test a submarine-launched ballistic missile (SLBM) before the vessel enters service. North Korea has previously presented SLBMs of increasing size, but has lacked a suitable submarine to launch them from.

Missile launches while the submarine is submerged represent a more demanding and operationally relevant capability than firing from the surface.

At the same time, a missile launch of any kind demonstrates only part of the capability required for a submarine like this to be effective at all. An operational submarine must also be able to deploy reliably, remain sufficiently difficult to detect, maintain its weapons, and execute missions under realistic conditions.

A vertical launch system (VLS) can provide dedicated capacity for certain missile types — potentially much larger ones — and may enable faster launches or larger salvos than a configuration relying exclusively on torpedo tubes. Torpedo tubes offer an alternative launch method, but with different constraints on weapon dimensions, handling, and firing procedures.

The forward four tubes are larger than the rear six on the submarine’s ‘turtle back.’ This would allow the boat to carry multiple types of missiles, possibly including a mix of short-range and longer-range submarine-launched ballistic missiles (SLBMs) and submarine-launched cruise missiles (SLCMs).

Testing both systems would be consistent with an effort to validate multiple elements of the submarine’s weapons architecture.

North Korea has pursued submarine-launched missiles for years. In March 2023, it reported a submarine-launched cruise missile test from the older 8.24 Yongung submarine. In January 2024, Pyongyang said it had fired Pulhwasal-3-31 strategic cruise missiles from that same vessel. The earlier sub is in the 2,000-ton-class and is understood to have only one or two vertical launch tubes.

North Korea’s description of the weapons as “strategic” cruise missiles should also be treated cautiously. North Korea’s long-range cruise missile program is well established and a nuclear payload is a major part of its ambitions, but how mature or reliable a nuclear warhead is for this application at this time isn’t clear. Regardless, ground, surface, and now subsurface-launched cruise missiles are a key part of North Korea’s broader deterrent architecture.

According to reports, Wednesday’s activity was the first publicly reported underwater North Korean missile-testing event since the January 2024 launch.

Compared to the 8.24 Yongung submarine, the Hero Kim Kun Ok has a larger hull and additional vertical launch tubes, but it still uses very dated diesel-electric propulsion, which presents hugely different endurance, acoustic, and operating constraints compared with nuclear propulsion or even modern diesel-electric submarine capabilities.

As to the expectation that Pyongyang may test an SLBM from the submarine before deployment, this would be a likely milestone toward North Korea fielding a credible sea-based nuclear deterrent.

North Korea is also pursuing a separate nuclear-powered submarine project, unveiled as under construction in March 2025. Its completion and operational timeline remain uncertain. Nuclear propulsion is a much bigger challenge, but if perfected, such a boat would be of considerably greater value, especially as a second-strike capability.

The latest submarine tests come amid a broader series of North Korean weapons demonstrations, including reported hypersonic missile tests on September 20 and October 3, as well as tactical ballistic missile launches earlier in October.

The sequence is consistent with Pyongyang’s effort to diversify its delivery systems and complicate military planning for South Korea, the United States, and Japan.

The activity also carries a diplomatic message. North Korea has repeatedly insisted that it will not abandon its nuclear weapons while the United States maintains what Pyongyang calls a hostile policy. It has also rejected the suggestion that adjustments to U.S.-South Korean military exercises would be sufficient to change the underlying relationship.

The tests also follow North Korea’s rejection of an apparent diplomatic opening from U.S. President Donald Trump after Washington sought to reduce tensions surrounding a U.S.-South Korean military exercise.

A submarine able to launch missiles from less predictable locations complicates defensive planning for South Korea and the United States. The challenge extends beyond intercepting missiles after launch to detecting and tracking the submarine before it reaches a potential firing position. Even a partially capable vessel places additional demands on potential adversaries.

Were things to ‘go hot’ on the Korean Peninsula, any submarine capable of carrying strategic weapons would be at the top of the targeting list for Pyongyang’s adversaries. A submarine based on the archaic Romeo class design would be fairly easy to track from the time it leaves its berth. This is especially the case bearing in mind the sophisticated nature of South Korea’s anti-submarine capabilities.

Future submarines will become increasingly more challenging, however. That problem could intensify if future North Korean boats make more use of Russian assistance in developing their capabilities. Submarine technology is supposedly part of the payment to Pyongyang for its help in the war in Ukraine. This could become a much larger problem, even if Moscow were to provide North Korea with advanced Kilo class boats, for example.

For now, provided that the Hero Kim Kun Ok launched the missiles, which seems most likely, this would indicate that North Korea is advancing weapons integration aboard a submarine intended to expand its offensive naval capabilities. The fact that the Hero Kim Kun Ok is now at sea also signals progress toward deployment.

Whatever the ultimate operational effectiveness of the Hero Kim Kun Ok and its emerging missile armament, Pyongyang continues to demonstrate incremental improvements to its submarine forces.

Contact the author: thomas@thewarzone.com

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The U.S. government set off conventional explosives inside a tunnel deep in the Nevada desert this week in a test designed to replicate a so-called “decoupled” nuclear detonation. Data collected is now being used to help improve methods for detecting this kind of nuclear testing. Just earlier this year, American authorities accused China of using decoupling to conceal new nuclear tests despite the country’s stated moratorium on such activities.

The test, which involved the use of chemical high-explosives and radiotracers, was conducted yesterday inside P Tunnel in Area 12 of the Nevada National Security Site (NNSA), according to a press release from the National Nuclear Security Administration (NNSA). The NNSS, which is situated within the boundaries of the U.S. Air Force’s Nevada Test and Training Range (NTTR), is used for a wide variety of testing purposes today. An agency under the Department of Energy, NNSA’s main jobs are to oversee the development and production of nuclear weapons, as well as manage America’s nuclear deterrent stockpile.

“This experiment is especially focused on further enhancing the U.S. capabilities to detect a ‘decoupled’ explosion,” per NNSA’s release. “Data collected from the experiment will be used to validate scientific models and refine algorithms that are critical to U.S. nuclear explosion detection efforts.”

“Just as a stealth aircraft looks smaller on radar, decoupling can greatly muffle the signals detected by nuclear detection sensors, making a large explosion appear smaller,” the release explains. “In a conventional, or ‘coupled,’ underground nuclear test, a device is placed deep in a hole in close contact with the rock, allowing much of the explosion’s shockwave to reach sensors. In a decoupled test, by contrast, the device is detonated inside a large underground chamber, substantially reducing the explosion’s seismic signature.”

“In this experiment, researchers gathered measurements using a broad suite of advanced sensors, including accelerometers, seismometers, infrasound sensors, electromagnetic sensors, chemical and radiotracer samplers, and meteorological sensors,” it adds. ”Together, these measurements will improve scientists’ understanding of the signatures produced by underground explosions and strengthen the United States’ ability to detect and characterize nuclear explosive events.”

The U.S. already maintains a U.S. Atomic Energy Detection Systems (USAEDS) network, which is overseen by the U.S. Air Force Technical Applications Center (AFTAC). USAEDS is made up of more than 3,600 sensors positioned around the world. USAEDS is also tied in with the International Monitoring System (IMS), which is managed by the organization responsible for overseeing the Comprehensive Nuclear-Test-Ban Treaty (CTBT). AFTAC also supports the mission to monitor for potential nuclear testing globally using a fleet of specially configured WC-135R Constant Phoenix aircraft. In addition, those planes are used to help keep watch for unusual spikes in atmospheric radiation that could point to nuclear or radiological accidents or other incidents leading to the spread of potentially dangerous radioactive material.

With regard to the USAEDS network specifically, “once a disturbance is detected underground, underwater, in the atmosphere or in space, the event is analyzed for nuclear identification, and the findings are reported to command authorities,” according to AFTAC’s website.

As mentioned, the U.S. government has accused its Chinese counterparts of using decoupling to conceal new nuclear testing, and NNSA’s press release draws explicit attention to these allegations. At the annual Conference on Disarmament in Geneva, Switzerland, in February, Thomas DiNanno, Under Secretary of State for Arms Control and International Security, said that China had conducted at least one such test at Lop Nur on June 22, 2020. The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) subsequently said the IMS had not detected an event matching that description at that location on that date. For its part, the Chinese government has denied the accusation.

The social media posts below include satellite imagery showing activity at Lop Nur that could point to new nuclear testing activities in recent years.

参考
Satellite Imagery Analysis of China’s Alleged 2020 Nuclear Test at Lop Nurhttps://t.co/aafvU5Szh7
CSIS 20260213
ROLES SAT ANALYSIS No.7　中国に核実験実施の動き ー Lop Nur核実験場の画像分析 ーhttps://t.co/n66yYk0hLg
ROLES 20250522

— KAROTASU (@type36512) May 24, 2026

While China is a signatory to the CTBT, the country has never ratified it. The Chinese government last acknowledged a critical-level nuclear test in 1996, after which a self-imposed moratorium was put in place, at least publicly. As an aside, the United States has also signed, but never ratified, the CTBT, and has a similar self-imposed moratorium on nuclear testing since 1992. It is worth noting that the treaty does not ban so-called sub-critical testing, which involves fissile material, but does not result in a full-fledged nuclear reaction.

Last week, The Wall Street Journal reported that the Trump administration has been holding new talks with the Chinese government regarding various aspects of the country’s massively and rapidly expanding nuclear arsenal, including the testing allegations. That story immediately preceded a state visit by China’s President Xi Jinping to Washington, D.C., to meet with Trump.

“The discussions between American and Chinese officials have centered on measures to reduce nuclear risks and haven’t been aimed at negotiating a formal arms-control pact, an effort Beijing has sharply rebuffed in the past,” according to that report. “The Trump administration has begun to highlight the possibility of implementing new verification measures.”

“Independent experts say seismic instruments might be placed on or near test sites,” The Journal‘s story also noted. “Another possibility, which was floated during the Biden administration, is to install radiation-detection equipment at test sites.”

NNSA’s announcement about the test at the Nevada National Security Site is certainly an example of the development underway already of new means of verification that could be deployed at sites around the world.

The United States has separately accused Russia of conducting lower-yield nuclear testing in secret in the past. Russia is a signatory to the CTBT and had previously ratified it. In 2023, President Vladimir Putin revoked that ratification in line with the provisions of a law passed by the country’s parliament, or Duma.

President Trump has also floated the idea of the resumption of U.S. nuclear testing in response to Russian and Chinese activities, though other U.S. officials have downplayed the possibility of doing so. The United States is otherwise in the midst of a huge nuclear modernization effort that impacts the air, sea, and land-based legs of the deterrent triad. American authorities are also now pursuing these efforts in an environment fully unbounded by relevant arms control agreements following the sunset of the New Strategic Arms Reduction Treaty (New START) earlier this year.

The Russian government has said it is ready to conduct new nuclear tests if the United States pursues this course of action. The last official nuclear test in Russia came in 1990 right before the fall of the Soviet Union.

“It takes nuclear expertise to detect nuclear activities and experiments like these [to] ensure America remains unmatched in detection,” NNSA Administrator Brandon Williams said in a statement yesterday in light of the test in Nevada. “The Trump Administration has made it clear that the United States will lead from a position of strength. You cannot evade American innovation. With this experiment, we are sending a clear message: under this administration, America will never be outmatched.” 

Contact the author: joe@twz.com

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