It is largely assumed that, despite the size of the North Korean Navy's submarine force (second only to the United States on paper), the underwater fleet is largely outclassed by more modern submarine fleets seen globally. However, the force still supplies some tactical and strategic value as it can be used in a harassment and deterrent measure when pressed while also posing a viable threat to South Korean surface ships (both commercial and military in nature).
There is also an improved version of the Sang-O-class as the "Sang-O II" (also "K-300"), its existence first reported in 2011. These boats are slightly larger in dimension and heavier in displacement, adding to increased operational ranges and more internal volume for stores and special mission equipment. Its propulsion system not entirely known as it could be carried over from the earlier Sang-O design or of an all-new local endeavor.
The Sang-O stands as the largest locally-constructed submarine group available to the North Korean Navy. One example was captured by the South Korean Navy on September 18th, 1996 when it ran aground while spying near Gangneung. The vessel landed three special operations personnel and ran aground during the extraction phase of the mission. During the ensuing operation to collect the enemy forces (who had abandoned their submarine), twelve South Koreans were killed and twenty-four North Koreans perished. One was captured alive along with the abandoned submarine.
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