KSS-III Submarine (Dosan Ahn Changho-class)

The conventional submarine that carries ballistic missiles — South Korea's KSS-III (Dosan Ahn Changho-class) is a large, indigenous, air-independent-propulsion boat with a feature almost unheard of outside nuclear-powered navies: a vertical launch system for submarine-launched ballistic missiles. That gives Seoul a survivable, undersea conventional-strike capability aimed at North Korea, on a diesel-electric submarine built almost entirely at home. Later boats add lithium-ion batteries and more missile cells, marking South Korea's arrival as one of the world's most capable non-nuclear submarine builders.

Overview

The KSS-III is a class of large diesel-electric attack submarines (SSK) designed and built in South Korea — jointly by Hanwha Ocean (formerly Daewoo/DSME) and HD Hyundai Heavy Industries — under the third phase of Korea's domestic submarine program (also called Jangbogo-III). Two features set it apart. First, air-independent propulsion (AIP) via fuel cells (derived from the German technology in Korea's earlier KSS-II boats) lets it stay submerged far longer than a conventional submarine. Second, and unusually, it carries a vertical launch system (VLS) sized for submarine-launched ballistic missiles — the conventionally-armed Hyunmoo family — giving South Korea a survivable undersea strike option against land targets, a capability normally associated with nuclear-powered ballistic-missile submarines. At roughly 3,000–3,750 tonnes submerged it is among the largest non-nuclear submarines in the world, and it is being built in successive, increasingly capable batches.

Development

The KSS-III initiative runs across three batches between roughly 2014 and 2029+, jointly designed by DSME (now Hanwha Ocean) and HD Hyundai HI, per Wikipedia and GlobalSecurity. The lead boat, ROKS Dosan Ahn Changho (SS-83), was launched in 2018 and commissioned in 2021 (the first ~3,000-ton-class indigenous Korean submarine able to fire SLBMs); the second, ROKS Ahn Mu, commissioned in 2023, and a third followed, completing Batch I (six VLS cells each). Batch II — launched from 2025 (e.g. Jang Yeong-sil) — lengthens the hull, increases the VLS to ten cells, adds lithium-ion batteries (for greater submerged endurance and speed) and more indigenous combat systems, per Army Recognition and 19FortyFive. Korea has also publicly tested underwater launch of a Hyunmoo ballistic missile from the class — demonstrating the SLBM capability that makes the KSS-III distinctive. The program reflects both deterrence (a survivable strike option against North Korea) and South Korea's ambition to be a top-tier submarine exporter.

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