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South Korea Launches Second KSS-III Batch-II Submarine, ROKS Seo Hui
Confirmed
In Short: The Republic of Korea Navy launched the second KSS-III Batch-II submarine, ROKS Seo Hui, at Hanwha Ocean's shipyard in Geoje.
The Republic of Korea Navy (ROKN) and South Korea’s Defense Acquisition Program Administration (DAPA) held a launching ceremony for the fifth overall KSS-III diesel-electric submarine, ROKS Seo Hui, at Hanwha Ocean's Okpo shipyard in Geoje on Tuesday, November 3.
ROKS Seo Hui is the second vessel in the Batch-II program, following the lead submarine, ROKS Jang Yeong-sil, which was launched on October 22, 2025, and is due for delivery at the end of 2027.
The submarine, named after Seo Hui, a distinguished statesman of the Goryeo Dynasty, reflects South Korea's efforts to increase the domestic content of its naval platforms and onboard systems.
ROKS Seo Hui is approximately 89 meters long and has a displacement of approximately 3,600 tonnes, larger than the Dosan Ahn Chang-ho class, providing ample capacity for weapons and onboard equipment.
The vessel carries 70 types of domestically developed equipment, 12 more than on the KSS-III Batch-I boats, and is designed to improve export competitiveness.
Upgrades to the combat and sonar systems are intended to help the submarine identify multiple targets at long range, enhancing its operational capabilities.
The submarine features advanced batteries that extend both submerged endurance and the time the submarine can operate at maximum speed.
The Navy named the submarine after Seo Hui, recognizing his outstanding military and diplomatic achievements and spirit of overcoming national crises, reflecting the stature of a state-of-the-art submarine that serves as a key asset for defending the nation’s waters.
What this adds
The ceremony marks a significant milestone in South Korea's indigenous submarine development program, highlighting the country's technological advancements and self-reliance in naval defense.
What's confirmed
- The Republic of Korea Navy (ROKN) and South Korea’s Defense Acquisition Program Administration (DAPA) held a launching ceremony for the fifth overall KSS-III diesel-electric submarine at Hanwha Ocean's Okpo shipyard in Geoje on Tuesday, November 3.
- The future ROKS Seo Hui is also the second Batch-II boat under the KSS-III class, which is also known as the Dosan Ahn Changho-class.
What's still developing
- Indigenously designed and built in South Korea, ROKS Seo Hui was launched following the award of a construction contract in 2021, a steel-cutting ceremony later that year, and a keel-laying ceremony in 2024.
- The Jang Bogo-III Batch-I program comprises three 3,000-ton-class submarines: Dosan Ahn Chang-ho (SS-083), Ahn Mu (SS-085) and Shin Chae-ho (SS-086).
- ROK Navy submarines are named after respected figures who contributed to the development of military power, maritime power, and science and technology, or who fought against foreign forces and participated in the independence movement.