An attack submarine or hunter-killer submarine is a submarine specifically designed for the purpose of attacking and sinking other submarines, surface combatants and merchant vessels. In the Soviet and Russian navies they were and are called "multi-purpose submarines". They are also used to protect friendly surface combatants and missile submarines. Some attack subs are also armed with cruise missiles, increasing the scope of their potential missions to include land targets.
The Republic of Korea Navy, also known as the ROK Navy or South Korean Navy, is the naval warfare service branch of the South Korean armed forces, responsible for naval and amphibious operations. The ROK Navy includes the Republic of Korea Marine Corps, which functions as a branch of the Navy. The ROK Navy has about 70,000 regular personnel including 29,000 Republic of Korea Marines. There are about 140 commissioned ships in the ROK Navy. The naval aviation force consists of about 70 fixed-wing and rotary-wing aircraft. The ROK Marine Corps has about 300 tracked vehicles including assault amphibious vehicles.
The Korean Attack Submarine program, KSS meaning Submarine, is a three-phased project to build up the Republic of Korea Navy 's attack submarine arsenal. Before the KSS program, the submarine fleet of the ROK Navy consisted of midget submarines, such as the Dolgorae class submarine and SX 756 Dolphin class submarine, which had limited capabilities for inshore operations. The KSS program sought to acquire submarines that can deter hostile submarines and surface ships; protect friendly naval bases and sea shores communications; carry out reconnaissance missions.
The Type 209 is a range of diesel-electric attack submarines developed exclusively for export by Howaldtswerke-Deutsche Werft of Germany. Five class variants, including modifications thereof, have been successfully exported to 15 countries, with 68 submarines being built and commissioned to five different variants between 1971 and 2021. More boats have been built to modified designs.
ROKS Jang Bogo (SS-061) is the lead ship of the Jang Bogo-class submarine of the Republic of Korea Navy, and was the first submarine to serve with the navy. It is one of the Type 209 submarines built for export by Germany.
The Jang Bogo-class submarine or KSS-I is a variant of the Type 209 diesel-electric attack submarine initially developed by Howaldtswerke-Deutsche Werft (HDW) of Germany, intended for service with the South Korean Navy and Indonesian Navy. A Daewoo (DSME)-upgraded model of the Jang Bogo class Type 209 was exported by Korea to Indonesia in 2012, amid heavy competition from Russian, French, and German-Turkish consortiums including from Germany's original Type 209. The variant was considered for possible purchase by Thailand as well, as both newly built and second-hand options. The class is named for ancient Korean maritime figure Jang Bogo.
The Nagapasa class is an upgraded variant of the Jang Bogo class, also known as Improved Chang Bogo. The vessels were built by the South Korean Daewoo Shipbuilding & Marine Engineering (DSME) and the Indonesian PT PAL. As of 2021, six ships have been planned, which were divided into two batches. Batch 1 consists of three ships and all are already commissioned. Batch 2 also consists of three ships that are in the early development stage. The class is named for weapon of Indrajit, Nagapash.
ROKS Sejong the Great (DDG-991) is the lead ship of her class of guided missile destroyer built for the Republic of Korea Navy. She was the first Aegis-built destroyer of the service and was named after the fourth king of the Joseon dynasty of Korea, Sejong the Great.
ROKS Seoae Ryu Seong-ryong is the third ship of the Sejong the Great-class destroyers built for the Republic of Korean Navy. She was the third Aegis-built ship of the service and was named after a scholar-official of the Joseon Dynasty of Korea, Seoae Ryu Seong-ryong.
ROKS Dae Jo-yeong (DDH-977) is a Chungmugong Yi Sun-sin-class destroyer in the Republic of Korea Navy. She is named after Dae Jo-yeong.
ROKS Wang Geon (DDH-978) is a Chungmugong Yi Sun-sin-class destroyer in the Republic of Korea Navy. She is named after Wang Geon.
ROKS Eulji Mundeok (DDH-972) is the second ship of the Gwangaetto the Great-class in the Republic of Korea Navy. She is named after Eulji Mundeok.
ROKS Yi Cheon (SS-062) is the second ship of the Jang Bogo-class submarine of the Republic of Korea Navy, and was the second submarine to serve with the navy. She is one of Jang Bogo-class submarines to be built in South Korea.
ROKS Choe Museon (SS-063) is the third ship of the Jang Bogo-class submarine of the Republic of Korea Navy, and was the second submarine to serve with the navy. She is one of Jang Bogo-class submarines to be built in South Korea.
ROKS Lee Jongmoo (SS-066) is the fifth ship of the Jang Bogo-class submarine of the Republic of Korea Navy, and was the fourth submarine to serve with the navy. She is one of Jang Bogo-class submarines to be built in South Korea.
ROKS Jung Woon (SS-067) is the sixth boat of the Jang Bogo-class submarine of the Republic of Korea Navy. She is one of Jang Bogo-class submarines to be built in South Korea.
ROKS Yi Sun-sin (SS-068) is the seventh boat of the Jang Bogo-class submarine of the Republic of Korea Navy. She is one of Jang Bogo-class submarines to be built in South Korea.
ROKS Na Dae-yong (SS-069) is the eighth boat of the Jang Bogo-class submarine of the Republic of Korea Navy. She is one of Jang Bogo-class submarines to be built in South Korea.
ROKS Yi Eokgi (SS-071) is the ninth and last boat of the Jang Bogo-class submarine of the Republic of Korea Navy. She is one of Jang Bogo-class submarines to be built in South Korea.
ROKS Shin Dol-seok (SS-082) is the ninth boat of the Sohn Won-yil-class submarine in the Republic of Korea Navy. She is named after the general, Shin Dol-seok.
South Korea 
