South Korea Launches First Changbogo-III (KSS-III) Batch-II Submarine — Jang Yeong-sil

South Korea Launches Next-Generation Changbogo-III Submarine

Mohd Hanif Ismail - : Oct 27, 2025 - : 5:34 pm

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South Korea has on 22 October 2025 launched the Republic of Korea Navy’s (ROKN) first Changbogo-III (KSS-III) Batch-II submarine, a larger and more capable evolution of the Dosan Ahn Changho class that underscores Seoul’s accelerating drive to indigenise advanced naval platforms. The boat, named ROKS Jang Yeong-sil (SS-087), was slid into the water at Hanwha Ocean’s Geoje shipyard in the country’s southeast, beginning a programme of harbour trials and sea tests ahead of an expected commissioning window in 2027.

The Batch-II design represents a meaningful capability upgrade over the Batch-I boats. Most visibly, the Jang Yeong-sil is reported to displace roughly 3,600 tonnes and integrates South Korea’s first large-format lithium-ion battery propulsion system for a diesel-electric submarine, a move intended to boost submerged endurance and tactical speed compared with conventional lead-acid installations. Equally significant, the Batch-II boats are fitted with ten vertical launch system (VLS) cells — up from the six K-VLS cells on earlier boats — giving the class enhanced missile carriage for land-attack and strategic-deterrent options. These technical details were confirmed at the launch and in official materials released by industry and defence authorities.

According to Hanwha Ocean and the Defence Acquisition Program Administration (DAPA) — the principal state buyer and programme manager — the Batch-II tranche is the next phase of the long-running KSS-III programme that aims to deliver a force of indigenously designed 3,000-plus-ton submarines to the ROKN. The Batch-II contract awards were previously reported with an estimated overall programme value in the region of KRW ₩1.11 trillion for early Batch-II work (approximately $775 million at recent exchange rates). The launch of Jang Yeong-sil was described by Hanwha as the shipyard’s first fully domestic KSS-III Batch-II build, a milestone in South Korea’s shipbuilding and defence-industrial maturation.

Strategically, the arrival of a Batch-II KSS-III with lithium-ion propulsion and expanded VLS capacity amplifies Seoul’s undersea posture in the Taiwan Strait and wider East Asian littorals. The improvements increase patrol endurance and weapons flexibility, enabling operations deeper and longer in contested waters and complicating adversary anti-submarine warfare (ASW) calculations.

Operationally, the ROKN will subject Jang Yeong-sil to an intensive programme of builder and acceptance trials before handing the boat over for commissioning. The typical path — builder tests, harbour acceptance and progressive sea-trials — will validate the new lithium-ion modules, the ten-cell VLS and the onboard combat systems under realistic conditions. If trials proceed to plan, the Batch-II boats will enter service in the latter half of the decade and become a core element of South Korea’s deterrent and power-projection toolkit.