A close-up view of the No. 841 Hero Kim Kun Ok under the security canopy, the 8.24 Yongung. The top of the conning tower is just visible in the opening of the canopy, May 30, 2025. Copyright © Airbus DS 2025. Image may not be republished without permission. Please contact imagery@csis.org.Key Findings
Almost two years since its launching, North Korea’s first true ballistic missile submarine, the No. 841 Hero Kim Kun Ok, is not yet fully operational.
Kim Jong-un considers the No. 841 Hero Kim Kun Ok a major component of not only “three-dimensional naval battles,” but also as the second leg of North Korea’s developing nuclear triad capable of “preemptive or retaliatory” strikes.
The long delay in operational has likely frustrated Kim Jong-un and his “ambitions for a modern navy.”
If the No. 841 Hero Kim Kun Ok conversion from a Type 003 attack submarine into a ballistic missile submarine proves to be successful, its operational debut could come within the next 6 to 12 months.
Satellite imagery acquired several weeks ago shows that North Korea’s first true diesel-electric ballistic missile submarine (SSB) the No. 841 Hero Kim Kun Ok, which launched in September 2023, is not yet fully operational and is not known to have put to sea for any significant length of time. Even with the launching of the Choe Hyon and Gang-Gang-gon (Kang Kon) guided missile destroyers (DDGHM) this year-long delay has likely frustrated a major component of Kim Jong-un’s “ambitions for a modern navy.”1
Kim’s identifying the No. 841 Hero Kim Kun Ok as a “standard type of tactical nuclear submarine” is a clear indication he considers it a major component not only of “three-dimensional naval battles” but also of the second leg of North Korea’s developing nuclear triad:
“…this submarine constitutes a menacing means as it is capable of carrying a large number of means for delivering nukes of various powers and of launching a preemptive or retaliatory strike at the hostile states in any waters.”2
Following the launch of No. 841 Hero Kim Kun Ok on September 6, 2023, during a ceremony attended by Kim Jong-un, the new submarine was subsequently moved into the graving dock at the Sinpo Shipyard. It remained there for approximately a year while significant construction and fitting out work continued. The specified nature of this work is unknown, as the submarine was quickly concealed beneath a security canopy to prevent overhead observation. Once this phase of work was apparently complete, the submarine was relocated to the secure boat basin at the Sinpo South Shipyard around December 2024. Here it displaced the 8.24 Yongung (August 24th Hero) experimental ballistic missile submarine (SSBA) beneath that basin’s security canopy.
Overview of the Sinpo South Shipyard’s secure boat basin showing the No. 841 Hero Kim Kun Ok under the security canopy, the 8.24 Yongung along the north pier, and what is believed to be an infiltration mothership on the east side of the basin, May 30, 2025. Copyright © Airbus DS 2025. Image may not be republished without permission. Please contact imagery@csis.org.A satellite image acquired on May 30, 2025, shows the No. 841 Hero Kim Kun Ok under the security canopy, with the top of the conning tower partially visible through an opening. Except for a small unidentified object, which has been present for approximately five months, the dock alongside the submarine is empty, and minimal activity has been observed here this year.
A close-up view of the No. 841 Hero Kim Kun Ok under the security canopy, the 8.24 Yongung. The top of the conning tower is just visible in the opening of the canopy, May 30, 2025. Copyright © Airbus DS 2025. Image may not be republished without permission. Please contact imagery@csis.org.Kim Jong-un’s description of the No. 841 Hero Kim Kun Ok as the first “child of the great cause of building an advanced marine power,” his intention to “promote the work of converting all medium-sized submarines into attack ones,” and the “building of nuclear-powered submarine so as to develop our Navy into a service of the world’s marine power” may be indications that the No. 841 Hero Kim Kun Ok will not only serve as the lead vessel in a new class of nuclear armed submarines but also as an experimental submarine that may serve to test the installation of various new types of missile or potentially a nuclear powerplant.3
Precisely when the No. 841 Hero Kim Kun Ok will become operational is unclear. If its conversion from a Type 003 attack submarine into a ballistic missile submarine proves to be successful, its initial operational debut could come within the next 6 to 12 months. True “blue water” operations, if achievable, would likely take several years. Regardless, it would not be unusual for North Korea to conduct a submerged missile launch for propaganda purposes by the end of the year.
The May 30, 2025, satellite image also shows the 8.24 Yongung SSBA docked along the north pier of the basin. Notably, there are three objects on the deck immediately aft of the conning tower. One of these is cylindrical with rounded ends and measures approximately 3.5 by 1.2 meters. The purpose of this object is unknown. It may simply be related to ongoing work aboard the submarine. Alternately, it may represent a nascent effort to develop a small submarine dry deck shelter (DDS) or submarine rescue chamber (SRC). The Korean People’s Navy’s sole submarine rescue capability was lost with the decommissioning and breaking of the sole Kowan class submarine rescue vessel (ASR) years ago.
A close-up view of the 8.24 Yongung SSBA showing three objects on the deck immediately aft of the conning tower, May 30, 2025. Copyright © Airbus DS 2025. Image may not be republished without permission. Please contact imagery@csis.org.Joseph S. Bermudez Jr. is a Senior Fellow for Imagery Analysis with the iDeas Lab and Korea Chair at the Center for Strategic and International Studies.
Victor Cha is President of the Geopolitics and Foreign Policy Department and Korea Chair at the Center for Strategic and International Studies.
Jennifer Jun is an Associate Fellow and Project Manager for Imagery Analysis with the iDeas Lab and Korea Chair at the Center for Strategic and International Studies.
Headline image Copyright © Airbus DS 2025. Special thanks to Seungjun Yeo for markups.
Related