Though North Korean military capabilities are mostly kept classified, it was reported that North Korea maintains 40 Sang-O-class submarines as of February 2021.
The Sang-O class was introduced in 1991, produced at Bong Dao Bo Shipyards in Sinpo.[1]
A single unit was captured by the Republic of Korea Navy (South Korea) after it ran aground on 18 September 1996 in the Gangneung submarine infiltration incident.
The seized Sang-O-class submarine was placed on display at Unification Park near Gangneung, which was opened on 26 September 2001.
The Sang-O class was reported to be larger than a midget submarine, but smaller than the Romeo and Whiskey-class submarines.[2] They are usually equipped with four torpedo tubes and 16 mines, but some are unarmed and are used to carry North Korean commandos.[3]
It was reported in March 2011 that a new version of the Sang-O class had been deployed in North Korea.[4] Satellite imagery from 2005 suggests the Sang-O II / K-300 may have been produced at the Mayang-do naval base and fitted out at the dry docks located at 39.9978 N, and 128.20019 E.[5]
Other footage of the nearby docks of Sinp'o appear to depict the Sang-O II / K-300 as early as 2004 (at 40 01'31.20"N 128 09'55.80"E). Subsequent satellite imagery shows the Sang-O II / K-300 deployed to the Ch’aho-rodongjagu submarine Navy Base at 40.205441 N 128.649524 E on North Korea's east coast.[5]
According to the KPA Journal, the decision to develop a larger, improved version of the Sang-O came in the late 1990s or early 2000. The Sang-O II / K-300 is a stretched version of the original Sang-O class with an approximate length of 39 to 40 metres and a corresponding surface displacement of approximately 300 to 340 tons.
The increased length and internal volume would suggest an increase in the operational range of the submarine and troop/equipment carrying capabilities. Top speed is also reported to be higher in the new model, meaning an improved propulsion system is possibly housed in some of the extra length.