In brief
South Korea’s Navy will perform a launch ceremony for the Seo Hui, the second vessel of its Jang Bogo‑III Batch‑II attack‑submarine class, at Hanwha Ocean Co.’s shipyard in Geoje. The submarine, equipped with an enhanced ballistic‑missile launch system and a hybrid diesel‑electric propulsion system with lithium‑ion batteries and air‑independent propulsion, will be delivered to the fleet in 2028 following tests.
South Korea's Navy is preparing to launch the Seo Hui, a 3,600‑ton attack submarine, at Hanwha Ocean Co.’s shipyard in Geoje on Tuesday, 3 November 2026. The ceremony will mark the submarine’s first entry into the water and showcase its upgraded capabilities for undersea deterrence.
The Seo Hui is the second vessel in the Jang Bogo‑III Batch‑II program, following the Jang Young‑sil lead boat that was launched in October 2025. The Batch‑II submarines are larger and longer than the 3,000‑ton Batch‑I class that is currently in service. According to the South Korean Navy statement jointly released by the Defense Acquisition Program Administration, the new boats are designed to enhance the navy’s ballistic‑missile delivery and submerged endurance.
During the launch ceremony, the Seo Hui will be moved into the water for the first time, marking a milestone in South Korea’s growing indigenous submarine‑building program. The shipyard, located 330 kilometres southeast of Seoul, has been the site of the navy’s latest undersea craft construction for several years.
One of the key upgrades on the Seo Hui is its expanded vertical launch system, capable of firing submarine‑launched ballistic missiles (SLBMs). The navy said that the system expands the submarine’s strike envelope and strengthens the country’s deterrence posture against maritime threats around the Korean Peninsula.
According to the Navy statement, the submarine’s advanced sensor suite serves as the vessel’s “eyes and ears.” This suite includes periscopes, sonar arrays, and communication systems that allow the ship to detect and track surface and subsurface contacts while hidden beneath the waves.
“The advanced sensor suite that serves as the submarine’s 'eyes and ears,'
