[7] In August 2016, during the annual joint US-South Korea military exercise, a submarine presumed to be this one launched what is believed to be a Pukguksong-1 (KN-11) ballistic missile into the Sea of Japan.

[13] US intelligence detected a new submarine being built at Sinpo which was considered a likely successor to Sinpo-B (Gorae) and labelled it Sinpo-C with an estimated submerged displacement of over 2,000 tons and with an 11-metre (36 ft 1 in) beam.

[1] 38 North also detected signs of submarine being built[14] and reported satellite imagery from 5 November 2017 indicates a diameter of 7.1 metres (23 ft 4 in).

[15] Tokyo Shimbun reported in September 2017, that new North Korean submarine in construction to displace 3,000 tons and have air-independent propulsion.

[21] As September 2023, there was one submarine of the class, Hero Kim Kun Ok, which was named after the supposed commander of KPA naval forces in the 1950 engagement they call the battle of Chumonchin Chan.

This particular weight would fit the category of a nuclear submarine, which had been a stated goal by Kim Jong Un at the 8th Congress of the Workers' Party of Korea.