In recent weeks, North Korean media have released images of a “newly built submarine” and subsequent analyses by researchers and think tanks theorize it is a second Sinpo-class ballistic missile submarine (SSB) that might be capable of launching nuclear ballistic missiles. If these reports are accurate, North Korea is showing the world that it can continue to achieve significant developments to its strategic nuclear capabilities despite maximum pressure and diplomatic dialogue at the highest levels.

To be sure, North Korea has a long way to go before this new SSB represents an actual operational threat. We have known about North Korea’s interest in developing a ballistic missile submarine and submarine-launched ballistic missile (SLBM) capability for years. The Gorae, North Korea’s first experimental Sinpo-class ballistic missile submarine, has been under development for the better part of a decade. North Korea has conducted roughly a half-dozen tests of its Pukkuksong 1 and 2 SLBMs (KN-11) since 2014, though all tests have been launched from ground facilities or submerged test platforms. North Korea has yet to demonstrate the ability to launch an SLBM from a submerged or surfaced SSB.

It is reasonable to assume that Kim Jong Un Kim Jong UnNorth Korean leader Kim apologizes over killing of South Korean official Pelosi knocks Trump over refusal to commit to peaceful transfer of power Satellite images indicate North Korea preparing for massive military parade MORE will continue to prioritize the development of an SSB and SLBM capability, given the resources directed to these programs. If the submarine becomes operational — which may take several years, given North Korea’s track record for fielding new capabilities — the SSB would represent a second leg of North Korea’s nuclear posture. The platform, if it eventually makes it to the sea without being detected, could increase Kim’s confidence in his nuclear deterrent by giving North Korea a first- or second-strike option in the event of a major conflict with the United States.

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Furthermore, Kim could calculate that this SSB gives him an additional tool for coercion vis-à-vis the United States and South Korea.

While the possibility of a North Korean submarine armed with nuclear missiles making its way to within striking distance of Guam or the United States homeland is without a doubt unsettling, in the short term, Kim’s options for the SSB’s employment are extremely limited. He would be assuming a very high risk to deploy his only SSB. Kim likely understands that if the submarine were to sortie, it would be a main focus for U.S., South Korean and Japanese detection efforts.

Unlike North Korea’s numerous ground-launch facilities and transporter-erector-launcher (TEL) vehicles, North Korea only has one SSB — and we know where it is. It is a signature national asset in that Kim personally has promoted the platform’s development and success. Additionally, its employment would immediately escalate any crisis, and the threat that it could be detected, targeted and destroyed at sea are all considerations that raise the bar for its employment to a very high level.

But just because the SSB cannot be readily used to directly threaten the United States does not mean it won’t serve as an asset for Kim going forward. The SSB doesn’t need to make it far beyond North Korea’s coastline to become an immediate threat to U.S. allies South Korea and Japan.

Submarines have served an important role in Kim’s calculus. With approximately 70 submarines, North Korea has one of the largest fleets of attack and mini submarines in the world. These submarines are aging and, by almost every metric, technologically inferior to the submarines of other navies. However, while these submarines are undoubtedly noisy, slow and unable to remain submerged for long distances, North Korea has been able to employ them to operational and strategic effect in the past.

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It was a North Korean “mini-sub” that sank the ROKS Cheonan in 2010. And in 2015, amid heightened tensions following the DMZ landmine attack, North Korea sortied approximately 70 percent of its submarines, or about 55 subs, from their pens in a show of force as inter-Korean negotiations were ongoing to resolve the crisis. These submarines are not going to win any prizes for modernity or stealth, but they are a significant tool for North Korea to menace navies and merchant ships operating around the Korean Peninsula. An SSB, deployed with additional North Korean submarines that could act as a screen, close to the North Korean coast could be used to target South Korean and Japanese homelands.

As with its other tests related to its nuclear and long-range ballistic missile programs, North Korea has refrained from overt testing of its nascent SLBM capability while diplomacy with the United States has been ongoing. Now that U.S.-North Korea diplomacy appears to be at an impasse, it is possible that Kim could continue to test the United States’ tolerance for its incremental return to ballistic missile tests, as it has with a spate of short-range ballistic missile tests this summer. Kim could put pressure on the United States and South Korea for a favorable negotiating position by conducting new tests of the Pukkuksong, or by demonstrating the ability to mate an SSB with an SLBM.

Such actions would demonstrate North Korea’s resolve to continue developing its nuclear program in spite of sanctions and the absence of a more flexible opening negotiating position from Washington. Perhaps more concerning, it would raise the stakes for the Trump administration’s North Korea policy, as it would be a return to the testing of capabilities that could actually be used one day to target the United States — an apparent threshold that recent statements from administration officials seem to indicate.

North Korean propaganda surrounding the new SSB should be interpreted as a very serious signal that the window for continued negotiation between the two countries is closing, and actual testing may indicate that the window has closed.

Sarah Vogler is a research analyst at CNA, an Arlington, Va.-based think tank focused on defense and national security issues. Her work involves North Korea, adversary calculus and leadership decision-making. The views expressed here are her own and do not reflect CNA or its sponsors. Follow her on Twitter @sarahvogler1.