Hanwha Ocean has launched ROKS Seo Hui, South Korea’s second 3,600-tonne KSS-III Batch-II submarine. Delivery to the Republic of Korea Navy is scheduled for 2028 after trials, with operational deployment to follow the Navy’s preparations.
The Navy and the Defense Acquisition Program Administration (DAPA) marked the launch on 3 November 2026. The ceremony took place at Hanwha Ocean’s Okpo shipyard in Geoje. The construction contract and steel cutting date back to 2021, followed by keel laying in 2024.
The approximately 89-metre submarine follows ROKS Jang Yeongsil, the first Batch-II vessel, which was also built by Hanwha Ocean. Its larger hull provides additional capacity for armaments and onboard equipment compared with the Batch-I design.
Hanwha Ocean said the submarine’s upgraded combat-management and sonar capabilities support the identification of multiple distant targets and precision attacks. Its domestically developed lithium-ion battery system allows longer underwater operations and more time at maximum speed. Noise-reduction measures are intended to improve stealth.
Backup equipment includes an auxiliary propulsion unit for manoeuvring if the main propulsion system fails. A penetrating periscope allows direct observation when the use of electro-optical sensors is restricted.
The submarine incorporates 70 types of domestically produced equipment, including the lithium-ion battery system. This is 12 more than on Batch-I vessels, with the expanded localisation intended to support reliable and timely follow-on logistics.
The vessel takes its name from Seo Hui, a Goryeo-era diplomat and strategist. Approximately 200 guests from government bodies, parliament and the defence sector attended the ceremony, with National Assembly Speaker Cho Jung-sik as guest of honour.
