“Recently, commercial satellite imagery has identified two new North Korean helicopter carrying frigates. These are the largest surface combatants constructed by the DPRK’s Korean People’s Navy (KPN) in 25 years and appear to be primarily designed to counter what Pyongyang sees as a growing threat from South Korea’s acquisition of submarines that began in the early 1990s. Moreover, these vessels may have an important secondary role: the protection of fisheries in the West and East Seas, which has obvious important security implications for the Republic of Korea, Japan and China. Their introduction into the North Korean fleet may also represent an evolutionary step in the development of naval strategy to include helicopter anti-submarine operations.”
Source: New North Korean Helicopter Frigates Spotted | 38 North: Informed Analysis of North Korea