Today, October 22, the South Korean Navy (ROKN) launched the first of its new KSS-III Batch II ballistic missile submarines during a ceremony held at the Hanwha Ocean shipyard in Geoje. The new unit, named ROKS Jang Yeong-sil (SS-087), was developed entirely with domestic technology, marking a new milestone in South Korea’s submarine capability development program, which traces its origins to the first locally built KSS-I submarines based on the Type 209 class.
The Jang Yeong-sil, displacing approximately 3,600 tons and measuring 86 meters in length, is the most advanced diesel-electric-powered submarine ever built for the South Korean Navy. Construction began in March 2023, and by the time of its launch, the shipyard and associated firms had met the deadlines set under the KSS-III Batch II program—also known as the Dosan Ahn Changho class—which aims to strengthen the country’s strategic deterrence capabilities in the region.
This new generation of submarines introduces substantial improvements over the previous Batch I models, including enhanced detection, stealth, attack, and survivability features. Among the most notable innovations is the inclusion of domestically developed lithium-ion batteries, which enable longer submersion time, reduced noise, and increased high-speed operational duration—thereby lowering the risk of detection during extended missions. The submarines also feature an expanded vertical launch system (VLS) capacity: while the Batch I variants have six VLS cells, the Batch II includes ten.
The submarine is also equipped with an auxiliary propulsion system that increases survivability, allowing it to resume operations in the event of a main system failure. Additionally, the Batch II incorporates 12 newly developed domestic systems, bringing the total number of localized components to 70—further strengthening South Korea’s technological independence amid export restrictions and intellectual property disputes. The submarine features a high degree of automation, enabling it to be operated by a reduced crew of 33 personnel, expandable to 55 if necessary.
It should be noted that the KSS-III ballistic missile submarine program—including both Batch I and Batch II—encompasses the construction of a total of six units. These represent the culmination of a shipbuilding effort that has been underway in South Korea for three decades, divided into three major phases: KSS-I with the acquisition and construction of Type 209-class submarines; KSS-II with units based on the Type 214; and finally, KSS-III, which includes the completed and commissioned Batch I submarines as well as the three Batch II vessels currently under construction.
Program progress and next steps
As for the remaining Batch II units, construction of the second submarine began in July 2024, with its launch expected in 2026. The third and final unit began work in October 2024, with completion projected for 2029 and delivery to the Navy around 2031, following sea and integrated systems trials.
From now on, ROKS Jang Yeong-sil will undergo a period of sea trials, system evaluations, and final acceptance, with official delivery scheduled for late 2027, when it will fully enter active service with the Republic of Korea Navy.
Finally, Admiral Kang Dong-gil stated: “I am confident that the Jang Yeong-sil, built with our own technology, will stand as a symbol of our leap toward an intelligent and elite naval force, and will fully fulfill its role as an essential component in the maritime defense of the Republic of Korea.”
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