South Korea (hereinafter called "Korea") is planning a large future conventional submarine, known as KSS-III and/or "Jangbogo III" displacing 3,000 tons (submerged).
"In January 2004 Choson Ilbo journalist Yu Yong-won reported that South Korean military authorities were considering the possibility of developing nuclear powered submarines after 2012. South Korean officials began to discuss the construction of nuclear submarines in May 2003, to be able to deal with "potential security threats from other strong powers in the region following Korean unification."
The South Korean Navy was reported to have formed a working group of some 30 specialists to initiate design work on the project. In August 2004, reporter Kim Yong-sam of the South Korean monthly news magazine Wolgan Choson reported that the Ministry of National Defense had approved concept designs in June 2003. An inter-agency working group for the project was said to include the ROK Navy, the Agency for Defense Development (ADD), and the Korea Atomic Energy Research Institute (KAERI).
According to one report, government officials stated that on 25 January 2004 Defense Department and the navy examined the construction of an atomic submarine positively, based on the report from May 2003. The nuclear propelled submarine of 4,000 ton class (SSX), after 2012, was said to be viewed positively in order for the Korean navy to cope with the threat in regard to the security of neighboring countries such as Japan and China.
"The Ministry of National Defense plans to deploy 3,000-ton [surfaced, 3,500 ton submerged] attack submarines after 2020, a two-year delay from the original Defense Reform 2020 initiative, a report said Sunday. ...The development of an [indigenous] 3,000 ton KSS-III submarine is a key part of the Navy's modernization programs. The KSS-III sub is to be fitted with domestically built submarine combat systems aimed at automating target detection, tracking, threat assessment and weapon control, according to Navy officials. The 1-trillion-won heavy attack submarine will also be armed with indigenous ship-to-ground cruise missiles and be capable of underwater operations for up to 50 days with an advanced Air Independent Propulsion (AIP) system, they said. The AIP system has improved the submarine's underwater performance and gives it stealth capability." full article