<Draft for Bemil of Chosun as of October 19, 2023>

On September 6, 2023, at Sinpho Shipyard, the North Korean Navy (KWA-Navy) launched a new type of submarine, described as a ‘tactical nuclear attack submarine’ and named ‘Hero Kim Kun Ok’ after a historical figure.

At the launch, North Korean leader Kim Jong Un declared that the KWA-Navy, currently rather small and weak, by becoming “nuclearized” would be much more powerful and capable of resisting its enemies, the US, Japan and the Republic of Korea (ROK). Kim is already boasting that this submarine provides a second-strike attack capability, but there are good reasons to doubt such a claim. Three things are clear f-rom this event, however: first, this submarine will likely be the prototype of a Hero Kim Kun Ok-class, with more submarines expected to be constructed; second, some 20 aging Romeo-class subs will be modernized following the lessons learned f-rom building the Hero Kim Kun Ok; third, the KWA-Navy intends to develop a nuclear-powered submarine, an SSN.

Naval experts believe that North Korea’s Sinpho Shipyard has been expanded, with larger piers and dry docks, and with submersible barges. The Hero Kim Kun Ok is a modified version of the Romeo-class submarine which has been enhanced in two main ways. Its conning tower has been enlarged f-rom 6.4m to 10.4m with the attachment of a missile section, and its length has been expanded to allow the loading of Pukuksong-class Submarine-Launched Ballistic Missiles (SLBMs), KN-23 series mini-SLBMs, Hwasal-2 Long-Range Cruise Missiles (LRCMs), and Haeil torpedoes supposedly capable of carrying nuclear warheads. The range of these weapons covers the Korean Peninsula, parts of Japan, and Guam.

Analysis of satellite images, together with others provided by North Korea’s Central Chosun Media, has revealed several technical and operational issues for the Hero Kim Kun Ok. Thus, the 10m extension has broken the original length/width ratio of 10:1, significantly reducing the strength of the submarine when launching SLBMs and LRCMs underwater. 

Also, Hero Kim Kun Ok’s center-of-gravity will be higher than the Romeo-class f-rom which it is derived, significantly affecting underwater operation and maneuvering, and it will likely prove very difficult to handle. During World War II, the Japanese Imperial Navy converted a battleship in-to a light aircraft carrier, in order to load more than 70 Zero-class aircraft. The vessel’s high center-of-gravity rendered its balance unmanageable under tough sea conditions.

Another problem concerns Hero Kim Kun Ok’s superstructural missile section, which is similar to China’s Type 092 and Type 094 SSBNs. This design may be unreliable for cold launching SLBMs and LRCMs f-rom the tubes in the upper superstructure. Presumably to address these flaws, Hero Kim Kun Ok has port and starboard stabilizers on its conning tower, but this means it will be much noisier than the teardrop design of US submarines such as the Virginia-class SSNs and the next-generation Columbia-class SSBNs. 

Kim Jong Un’s characterization of the Hero Kim Kun Ok as a tactical nuclear attack submarine is significant. It can be classified as an SSB-Plus, with its large superstructural missile section behind the conning tower, and it is probably intended as an intermediate phase, to establish safety and operational parameters, before developing SSNs and SSBNs. Clearly Kim’s plan is for the KWA-Navy to build nuclear-powered submarines in the near future, as soon as North Korea can obtain core technical support for nuclear-powered engines. Notably, on Kim’s recent visit to Russia he was accompanied by naval leaders.

Many naval experts were expecting North Korea to develop a strategic submarine, so the launch of tactical nuclear attack submarine, an SSB-Plus with a large superstructural missile section behind the conning tower, merits some discussion. 

North Korea apparently means to build as many Hero Kim Kun Ok-class submarines as it can, for operating in the shallows of the East Sea (aka the Sea of Japan). The website 38 North reported on September 8, 2023 that Sinpho South Shipyard has another submarine pen suita-ble for this purpose, and on September 11, 2023 that two aging Romeo class submarines were in dry dock for maintenance. These are probably undergoing shape remodeling and engine refits, and one or both of them will likely be moved soon to a larger pen for conversion to Hero Kim Kun Ok-class. 

The operational capabilities of the Hero Kim Kun Ok-class have yet to be demonstrated, however, and the prospect of the KWA-Navy being able to conduct a second-strike attack against ROK and US bases in South Korea and Japan is not an immediate threat. Ultimately, North Korea is seeking to counter the ROK-US Combined Defense Posture, which is based on conventional means, by deploying these submarines close to Sinpho port and using them to threaten a nuclear response to any first strike f-rom its enemies. In times of crisis, these submarines might also be used in a first strike against major strategic targets.

The deployment of North Korea’s Hero Kim Kun Ok-class submarines in the East Sea and the Western Pacific will impact the ROK Navy’s current underwater operations as well as its future submarine requirements. North Korea will likely depend upon quantity rather than quality in challenging the ROK-US Combined Forces Command. Some naval experts insist, nevertheless, that the Hero Kim Kun Ok-class submarines will attempt to implement an Anti-Access and Area Denial (A2/AD) strategy to deter more capable ROK and US underwater assets f-rom operating close to east coast of North Korea. In any case, the ROK’s sophisticated modern SSKs are not allowed to cross the Northern Limit Line on either side of the Korean Peninsula, this being the maritime equivalent of the Demilitarized Zone which forms the land border between the two Koreas. 

Although the weapons carried by the Hero Kim Kun Ok-class submarines have a regionally significant range, their technical flaws, especially their noisiness and the operational weaknesses arising f-rom their ad hoc construction designs, will limit their effectiveness, at least in the near term.

There has been some discussion about the possibility of the KWA-Navy using its Hero Kim Kun Ok-class submarines in a similar way to the Soviet Navy’s operational concept known as the Bastion Strategy. The Soviet Navy was unable to protect its SSNs and SSBNs f-rom US forces, except in its near sea underwater domain, which was achieved by building Kiev-class aircraft carriers with Anti-Submarine Warfare (ASW) helicopters and other ASW weapons to clear out the surface waters. Indeed, neither the Soviet Navy, nor its Russian successor has ever sent its SSNs and SSBNs in-to deep ocean waters, except for the Arctic Sea.

The US Naval War College Review has published a peer-reviewed research article in Spring 2017 on the Bastion Strategy, arguing that US or ROK underwater assets should be deployed near Sinpho and Mayangdo bases to monitor, track and chase KWA-Navy submarines, attacking them before they can mount a preemptive strike.

In any event, the ROK and the US need to decide how to respond to the launch of the Hero Kim Kun Ok ‘tactical nuclear attack submarine,’ since the KWA-Navy clearly intends to continue to develop this project, and they may get some assistance f-rom Russia. Kim Jong Un made a six-day visit to Russia in mid-September, meeting with President Vladimir Putin on September 13, 2023 at Russia’s Vostochny Cosmodrome spaceport. North Korea has begun to play its ‘Russia card,’ not least with respect to China. Kim is assumed to have promised artillery shells and rockets for Putin’s war in Ukraine, and in return he may get help with missile, space, and nuclear technologies. North Korea has tried and failed to launch satellites, and it is currently unclear whether it has mastered ICBM reentry or warhead miniaturization.

Reaction in the ROK to the launch of Hero Kim Kun Ok has been mixed. Some argue that since the project is obviously half-baked, at least so far, the best response is further diplomatic pressure against North Korea and Russia. At the fourth meeting of the Extended Deterrence Strategy and Consultation Group, held in Seoul on September 15, 2023, ROK President Yoon Suk Yeol criticized the recent collusion between North Korea and Russia, urging the international community to condemn it, and he also suggested that the ROK should talk with China about maintaining peace and stability. 

Popular media in the ROK take a different view, however, preferring a military response. Since Kim Jong Un has gone to Russia to try to obtain sophisticated modern missile and nuclear technologies which China would not provide, they argue that the best way to counter North Korean underwater platforms is for the ROK to build its own.

The ROK is currently building KSS-Ⅲ attack submarines, and many are now suggesting that these should be propelled by nuclear reactors. Nuclear-powered submarines enjoy much extended endurance for secret underwater operations, and such vessels would be effective in conducting the ROK’s ‘anti-exit’ strategy, as well as for platform-to-platform confrontation between the two Koreas. For the ROK to construct an indigenous SSN is still a big ask for the US, however, and the ROK may prefer to avoid upsetting the ROK-US alliance. Certainly. the US and its other allies have so far been quite cautious in their response to the KWA-Navy launching a ‘tactical nuclear attack submarine.’

There are hardliners, both in the ROK and the US, who will use the launch of the Hero Kim Kun Ok to argue for serious and escalatory military options, particularly in the light of Kim Jong Un’s obvious desire to acquire missile and nuclear technologies f-rom Russia. The problem which must be faced is not really the current state of North Korea’s underwater military capabilities, flawed as they clearly are, but its overweening ambition to acquire tactical and strategic nuclear attack capabilities which pose a genuine threat to the ROK, to Japan, to US forces in Korea, to US bases in the Western Pacific, and perhaps eventually to the continental US. Kim Jong Un will continue to develop new weapons and strike capacities. He will build his ‘nuclearized navy.’ The rather bizarre Hero Kim Kun Ok submarine is not the real issue, but sooner or later North Korean will have more worrying underwater platforms, such as autonomous extra-large unmanned underwater vehicles. This is why the ROK and its allies must decide now how to deal with Kim’s underwater ambitions, before the situation becomes more challenging.