North Korea Submarine Capabilities

North Korea maintains one of the world’s largest submarine fleets, with estimates for the total fleet ranging from about 64 to 86 submarines. North Korea maintains approximately 40 Sang-O-class (“Shark-Class”) coastal submarines (SCC), 20 Romeo-class conventional submarines (SS), 20 Yugo- and Yono-class mini submarines (SSM), and a single diesel-electric ballistic missile submarine (SSB) known as the Gorae-class (aka “Sinpo-class”),¹ and an SSB known as the Sinpo-C class (aka ROMEO-Mod class).² In 2020, open-source satellite analysis noticed an additional Midget Submarine and labeled it “Sinpo-D,” but its existence is yet to be announced by North Korea.³ Despite the size of North Korea’s submarine fleet, experts doubt that all of the country’s submarines are operational given the age of the vessels. The Korean People’s Navy (KPN) is the primary operator, with some assets falling under the control of North Korea’s primary foreign intelligence agency, the Reconnaissance General Bureau (RGB).⁴

Estimated Total Submarines in Fleet: 83

• Ballistic Missile Submarine (SSBNs): 2
• Nuclear-Powered attack submarines (SSNs): 0
• Diesel-electric attack submarines (SSKs): 0
• Air-independent propulsion (AIP) enabled: 1
• Coastal Submarines (SSCs): 40
• Conventional Submarines (SS): 20
• Mini Submarines (SSMs): 21

North Korea’s use of submarines, particularly for the purposes of espionage and infiltration, has precipitated a number of crises on the Korean Peninsula since the 1953 armistice. In 1996, a Sang-O-class submarine operated by the RGB ran aground near the South Korean city of Gangneung. The crew attempted to escape back to North Korea on foot and an ensuing 49-day manhunt led to the killing or suicide of every crew member, save one who was captured alive.^{5 6} In June 1998, a North Korean Yugo-class submarine became entangled in a fishing net in South Korean waters near the port of Sokcho: all crewmembers perished in an apparent murder-suicide that took place as the submarine was towed back to port.⁷ In November 1998, a North Korean mini submarine was spotted by South Korean patrol boats near Ganghwa Island and narrowly evaded interception by South Korean forces, causing embarrassment to North Korea.⁸

A serious naval incident occurred on 26 March 2010 with the sinking of the South Korean corvette ROKS Cheonan. The Cheonan, with a crew of 104, was attacked and sunk off the coast of Baengnyeong Island, near the Northern Limit Line. An international investigation concluded that a North Korean Yono-class mini submarine likely sunk the Cheonan in a torpedo attack.^{9 10} North Korea has vehemently denied the report’s conclusions, and no party has accepted responsibility for the attack.

While North Korea’s submarine fleet is largely comprised of small coastal submarines suitable for coastal defense, infiltration, and espionage missions, the Gorae SSB program suggests North Korea has plans to develop a strategic force. An operational SSB and submarine-launched ballistic missile SLBM capability could provide North Korea with additional options for nuclear launch, and a hedge against destruction of its land-based nuclear systems.¹¹ Given the Gorae’s reliance on diesel-electric engines and lack of an Air-Independent Propulsion (AIP) system, the submarine can only remain submerged for a few days. This limits the Gorae to an effective range of an estimated 1,500 nautical miles, holding South Korean and Japanese targets at risk but precluding its ability to attack U.S. mainland targets.¹²

In parallel with its SSB production, North Korea has also produced a solid-fuel SLBM, the Pukguksong-1, also called the KN-11. North Korea has built a submerged test barge to facilitate ejection tests without risking damage to North Korea’s lone ballistic missile submarine, and satellite imagery suggests a second test barge is under construction.¹³ The SLBM program progressed remarkably quickly. The first ejection test from a sea-based platform occurred in December 2014, and only about 20 months later North Korea successfully test-fired an SLBM from another underwater platform.^{14 15 16 17 18 19} All tests have been conducted near the eastern port of Sinpo on the Sea of Japan. ²⁰ A second submersible missile test stand barge is located at the Nampo Navy Shipyard on the west coast, but no known SLBM tests have been conducted at this site. ²¹ Subsequent tests of a larger solid-fueled missile, the Pukguksong-2, appear to involve a land-based variant of the Pukguksong-1 SLBM.^{22 23 24} On 2 October 2019, another SLBM, the Pukguksong-3, was launched from an underwater platform.²⁵ In April 2022, a Pukguksong-5 type was unveiled at a military parade.²⁶

On 20 October 2021, North Korea announced it had successfully launched an SLBM from a Gorae-class submarine off Sinpo.²⁷ It was detected to have flown about 600 kilometers, at an altitude of 60 kilometers.²⁸ The launch came after South Korea’s launch of an SLBM from the Dosan Ahn Chang-ho submarine in September 2021. The effects from the launch caused damage to the Gorae-class submarine and it was towed back to the pier. ^{29 30} Currently, it is believed to be operating at a normal capacity.

North Korea’s SLBM Test Site, Sinpo South Naval Shipyard

Gorae-Class

North Korea possesses one Gorae-class ballistic missile submarine, which was launched in March 2014. ³¹ The submarine, named the 8.24 Yongung (“August 24th Hero”), holds a crew of 35, features a top speed of 10 knots, is 66.75 meters long, and has a 6.7-meter-wide beam.³² It likely features diesel-electric propulsion, but does not feature an air-independent propulsion (AIP) system.^{33 34} This limits the Gorae’s capability as a survivable, second-strike nuclear deterrent, as it cannot remain submerged for more than a few days without surfacing. The Gorae appears capable of firing a single ballistic missile; it has been used as a test-fire platform for submarine-launched ballistic missiles (SLBMs), but it is unclear whether North Korea intends to deploy the Gorae as an operational system.^{35 36}

In late 2017, construction activity at North Korea’s Sinpo Shipyard led observers to believe that the country may be building a new SSB as a successor to the Gorae, called the Sinpo-C class within the U.S. intelligence community. ^{37 38} The new Sinpo-C class submarine features a wider range and may be able to accommodate a more advanced SLBMs. ³⁹

Sinpo-C-Class

North Korea possesses one Sinpo-C class ballistic missile submarine. On 21 August 2020, the South Korean National Intelligence Service reported that construction of the Sinpo-C class submarine was completed. ⁴⁰ It is estimated to be around 3,000 tons with the capacity to carry three or four ballistic missiles, possibly the Pukguksong-3. It likely features diesel-electric propulsion, and is purported to feature an Air-Independent Propulsion (AIP) system. If confirmed this would make this the first Korean People’s Navy (KPN) submarine with this technology.⁴¹

Sang-O-Class and Sang-O II Class

North Korea possesses approximately 40 Sang-O- and Sang-O II-class costal submarines. The Sang-O-class features a top speed of 9 knots, is 35 meters long, and has a 3.8-meter-wide beam.^{42 43} The Sang-O II-class is slightly longer and faster than its predecessor with a top speed of approximately 15 knots and a length of 39 meters. ⁴⁴ It likely features diesel-electric propulsion, but does not feature an AIP system.

Romeo-Class

The KPN’s aging fleet of 20 Romeo-class submarines is in an unknown state of operational readiness. The vessels remain the KPN’s only submarines capable of long-range patrols. The KPN first acquired 7 Romeo-class submarines from China in the mid-1970s, and then began producing the submarines domestically from 1976 until 1995, when production shifted in favor of the Sang-O-class.⁴⁵ Reports suggest that the KPN is seeking to acquire modern sonar and radar technology in order to retrofit some of the aging Romeo-class submarines. However, North Korea is also likely replacing many of these with newer Sang-O-class vessels. ⁴⁶ The majority of the Romeo-class fleet seems to be stationed on North Korea’s east coast. The Romeo-class submarine is 76.78 meters long, has a 6.72-meter-wide bean, and can travel up to 15.31 knots surfaced and 13.18 knots while submerged.⁴⁷

Yugo- and Yono-Class SSM

North Korea operates a significant number of mini submarines (SSM), referred to as the Yugo- and Yono-class. Estimates vary, but nearly 20 may be in service. ⁴⁸ The KPN began building Yugo-class submarines based on Yugoslavian designs in the 1960s. The Yugo-class submarine is 21 meters long and has a 3.1-meter-wide beam. It is equipped with two 533-millimeter torpedo tubes.^{49 50} These submarines can travel up to 12 knots while surfacing and 8 knots underwater.⁵¹ The Yono-class appears to be an improvement of the Yugo model, although Yugo submarines are still produced. The Yono-class submarine is 29 meters long and has a 3-meter-wide bean. It is also equipped with two 533-millimeter torpedo tubes. These submarines can move up to 8 knots underwater.⁵²

Sinpo-D Class

In December 2019, commercial satellite imagery indicated that a midget submarine, about 15 meters long, was attached to a submersible test barge off Sinpo. One analysis suggests that it might be a new type of midget submarine.⁵³

Imports

The KPN first acquired 7 Romeo-class submarines from China in the mid-1970s, and then began producing the submarines domestically from 1976 until 1995, when production shifted in favor of the Sang-O-class.⁵⁴ In 1990, North Korea acquired three scrapped Golf-class submarines from the Soviet Union, obtaining vertical launch technology.^{55 56}

Exports

North Korea has reportedly exported both physical vessels and designs of the Yono-class submarine to Iran and Vietnam. Iran’s Ghadir-class submarines are remarkably similar to the Yono-class submarines.⁵⁷ In addition, the Iranian Navy introduced and operates a North-Korean made Daedong B-class semi-submersible, also known as the Gijimi-class submersible. The Daedong-B class submarine is 12.5 meters long and can dive up to 20 meters in the water. It carries six to eight crew members and is equipped with two 324-milimeter torpedo launchers.⁵⁸