[Military Story] The Evolving North Korean Submarine

Preparation for SLBM on Sinpo and Romeo-class Improved Submarines
Possibility of Constructing Sinpo-C-class Ballistic Missile Submarines

During the Korean War, Kim Il-sung viewed the lack of submarine capabilities as the main reason for North Korea's defeat. Therefore, he actively considered the introduction of submarines thereafter. North Korea's submarine development progressed rapidly. Recently, they have developed a new 3000-ton class submarine and completed a submarine-launched ballistic missile (SLBM).

Romeo-class submarine of North Korea (Photo by Yonhap News)

The main submarines currently possessed by North Korea are the Sinpo-class and the Romeo-class upgraded new submarines. The Romeo-class upgraded new submarine is estimated to be 80 meters long, with a displacement approaching 3000 tons, and capable of carrying three SLBMs. It is comparable to South Korea’s Dosan Ahn Changho-class submarine (83.5 meters long, 3200 tons) and Japan’s Soryu-class submarine (84 meters long, 4200 tons).

This year as well, there are forecasts that North Korea will flaunt its power by launching an SLBM. If North Korea launches an SLBM, the likely timing is ahead of the founding day of the Workers' Party of Korea (October 10), one of North Korea’s four major holidays. It is also speculated that North Korea will test-fire the SLBM and publicize it to emphasize deterrence against South Korea and the United States while fostering internal unity.

In 2022, it was unusual that the presidential office, rather than the military, first disclosed North Korea’s SLBM launch preparations. At that time, the presidential office stated that President Yoon held a security situation briefing with his aides inside the plane before it took off for its return after completing a foreign trip. The presidential office’s proactive release of related North Korea information was interpreted as a message urging restraint against North Korean provocations. It is also seen as a ‘deflating’ strategy to reduce the impact of provocations even if North Korea actually fires an SLBM.

Recently, there is also analysis that North Korea is newly constructing a Sinpo-C-class ballistic missile submarine (SSB). On September 6 last year, North Korean State Affairs Commission Chairman Kim Jong-un first revealed the Sinpo-C-class SSB named Kim Gun-ok Hero Ship and declared an expansion of submarine missile launch capabilities. The 3000-ton Kim Gun-ok Hero Ship is a diesel-powered submarine equipped with 10 missile launch tubes. It is on par with Russian nuclear submarines targeting the U.S. mainland with nuclear missiles in the Bering Sea. However, the Joint Chiefs of Staff assessed that the Kim Gun-ok Hero Ship is an awkwardly enlarged version of an 1800-ton submarine, equipped with an excessive number of launch tubes, making it difficult to operate properly.

In May, the U.S.-based North Korea specialist media 38 North analyzed commercial satellite images of the Sinpo shipyard in South Hamgyong Province taken over several months and reported that a submarine of the same size as the Kim Gun-ok Hero Ship is under construction. After the jig used to lift submarine hull parts first appeared in images taken in late December last year, the number of jigs increased to three by mid-February. A jig is construction equipment used to lift parts and align them with other parts.

Images taken on March 31 captured submarine hull sections with diameters of 5.6 meters, 6.5 meters, and 7 meters. Welding and joining these sections would form the submarine hull. Two smaller hull sections were lifted by jigs, and the largest hull section was placed on a rail track for transportation. Considering the presence of a mobile gantry crane above, it appeared that the section would soon be moved to the main construction site. Recent images show that the largest hull section has been moved to the main construction site, and the gantry crane has shifted above the other smaller hull sections. Considering the sizes of the three hull sections, the submarine under construction appears to be the Sinpo-C-class with an 8.1-meter diameter. Meanwhile, the Kim Sun-ok Hero submarine, first revealed last September, remains docked and appears to be outfitting navigation equipment such as electronic devices.