North Korean submarine Hero Kim Kun Ok

In August 2016, the existence of a modern class of submarine, designated the was determined after the launch of a Pukguksong-1 (KN-11) ballistic missile into the Sea of Japan. Subsequently, in 2019, satellite imagery of a modified of about 3,000 tons displacement was shown to be under construction at Sinpo South shipyard. Analysis by 38 North indicates that it has been in the construction warehouse as early as 2014. Kim Jong Un visited the site of construction, deemed the Pongdae submarine factory in 2019, and declared that a "new era" for the Korean People's Navy was arriving within a span of "five to ten years". With 20 Romeo-class subs in the inventories of the North Korean navy, Kim described as a "rapid improvement of our national defense capabilities with nuclear deterrence as the core", with a long-term plan of modifying the rest of the Romeo subs. == Launching ==

The naming and launching ceremony of the submarine occurred at Sinpo shipyard on 6 September 2023, subsequently announced two days later on North Korean state media. Independent journalists were not given access to cover the event. It coincided with the 75th anniversary of the establishment of North Korea on 9 September 1948. The ship was named after a naval leader Kim Kun Ok, who claimed to have sunk the American cruiser in the Battle of Chumonchin Chan, despite the fact that Baltimore was never deployed to the Korean War and was in fact, decommissioned and mothballed in 1947. == Armament ==

Israeli missile researcher, Tal Inbar, said to NK News that the newly upgraded submarine can carry a combination of submarine-launched ballistic missiles (SLBMs) and cruise missiles with nuclear warheads. James Martin Center associate Dave Schmerler observed from the state media photos that the submarine has four large and six small missile hatches, the large ones capable of launching medium SLBMs like the Pukguksong-3 It is unclear whether North Korea has developed the warheads required for such weapons. It is also presumed that the sub is capable of launching an unmanned underwater vehicle designated the "Haeil", unveiled in March 2023. == Operational history ==

North Korean state media stated the submarine was intended to operate in the Sea of Japan. As of July 2025, satellite imaging of the submarine indicates that it has not gone on deployment, remaining in the same canopy, with a piece of probable equipment beside it for the past five months. Should the conversion from the Type 003 sub be successful, it's operational debut is estimated somewhere between the next 6-12 months. == Responses ==

In an interview by the Joint Chiefs of Staff of South Korea, one official raised question about the sub's capabilities, and that additional monitoring in coordination with the United States will continue in order to respond to provocations. The age of the Romeo-class design, first produced by the Soviet Union in 1957, raised questions as to the submarine's effectiveness if it were ever employed. Former US Government expert Vann Van Diepen described it as "noisy, slow, and having limited range." Joseph Dempsey, a researcher at the International Institute for Strategic Studies, described it as having "fundamental limitations and vulnerabilities." == References ==