Visions of the North Korean Mystery Frigate Soho

Our effort to reconstruct a plan of the mysterious North Korean Soho class catamaran-frigate.

In our last post, Unknown Warships of the Hermit Kingdom, we noted the almost complete lack of accessible photos of North Korea’s oddball fleet of ships. For one of the most mysterious of Korea People’s Navy (KPN) warships, we decided to fire up the creative department and work on a draft profile and deck plan. We are particularly thrilled with the result, which we think helps restore elements of the design of a unique warship that no longer exists.

The basic plans the Shipsearcher Identification Section’s (SIS) team of amateurs worked up may look whacky, but read on, and you will see that the Soho, pennant number 823, was no ordinary warship!

Soho draft general arrangement : waterline profile and overall deck layout. For all use please credit with a link to this site.

The Soho represented a radical departure for the North Korean regime’s naval construction. The ship that was completed at the Najin shipyards late in 1982 was a helicopter-carrying, missile-armed catamaran (twin hull). For its time, it was an ambitious concept, designed to perform multiple roles in an era when multiple hulls were not being used in the design of surface combatants. At 240 feet long and about 1,600 tons displacement, the Soho corresponded to what we might think of nowadays as a corvette, though it has usually been called a frigate by analysts. With a broad beam of over 50 feet, the ship also bears a resemblance to modern littoral combat ships, though her role did not seem to include landing assault forces. For a modern naval comparison, it is about the size of the 2005-activated Sea Fighter:

A sharp capture of FSF-1 Sea Fighter, a similarly-sized USN catamaran. The layout is much different.

Soho had a flush (single level) deck that spanned the two hulls. This was dominated by a helicopter flight deck, which took up almost half the space. Many questions remain about what was intended for the air complement – the helicopters the vessel was meant to operate. They would likely have extended the ship’s anti-submarine capabilities. One of the very few photos (Shared on Twitter from original Korean blog entry: shows a single Russian Mil Mi-4 helo (or possibly the Chinese Harbin Z-5 copy) on this large flight deck:

The remaining midships and forward sections held a multi-level deck structure, with navigation and command facilities, sensors, and communications gear. The crew were estimated to consist of about 200 officers and men. The primary armament consisted of four enormous STYX anti-ship missiles, contained in “dust-bin” style launchers.* These were likely reused from KPN Osa or Soju class missile boats.

An Osa 1 class missile boat similar to those in KPN service, launching a STYX anti-ship missile. The enormous STYX anti-ship missiles, also housed in four similar “dust-bin” style launchers, the 30mm Gatling gun (bow position) and the “drum-tilt” radar visible aft are all features that were reportedly found on the Soho. Credit: Bergenbier, Public domain, via Wikimedia Commons

The main gun, located on a raised area forward of the bridge, was a Russian 100mm 56 caliber variety, similar to that fitted on the earlier Najin class frigates. The Soho bristled with lighter weapons, such as 57 and 30 mm cannon, and included anti-submarine RBU-1200 5-barrelled mortars. Some sources also note depth charges held on rails on the stern deck.

100mm 56 Cal. B-34, similar to those fitted on North Korean warships, on display at the Estonian Maritime Museum, Tallinn, ca. 2012. Credit: MKFI, Public domain, via Wikimedia Commons

Little information is available about Soho’s career. She rarely ventured far from the protected waters off North Korea’s Eastern coastline. Reportedly, the ship was unstable, and may not have been safe in exposed waters further from the coast. Around 2009, Soho is believed to have been decommissioned and dismantled where she was originally built.

The only view currently sourced from Google Earth provider Maxar technologies, dates from 2004. Online there is also one 2006 view of the vessel taken from DigitalGlobe (see resources section for link) that shows the helicopter pad markings and has been used along with this one to create the deck arrangement scheme. The design would almost seem fantastical, except that elements of it are clearly distinguishable in these views.

Though this single unit’s design resulted in no similar naval construction, Soho does seem to have encouraged the North Korean regime to, in the early 2000s, embark on the construction of a series of smaller, faster catamarans: the Nongo class. This is all we have been able to find out about this strange ship. We would welcome any comments or help locating additional views of the Soho, giving us the opportunity to update our design based on new information. Read on for a section on the how we came up with our design, and some useful sources.

Soho design context and details:

Our interpretation of the design incorporates elements from the existing general arrangement profile view (or simplified rigging plan) of the Soho class (found in Jane’s Fighting Ships editions). The JFS drawing was not significantly updated from the 1990s until 2007. While the Soho remained an active warship, the JFS profile remained one of the most vague plans in their vast catalog of drawings.

One interpretation of the Soho, which is generally similar to the Jane’s Fighting Ships drawing. A similar rendering by the same designer shows a cut-back raked catamaran bow, with the fore deck projecting forward, but is not available for use. Credit: planeman, via wikipedia (Arabic language site).

Without much to go on, we created the only general arrangement-type deck plan (overhead view) we are aware of for the Soho. This view accurately sites major deck features, with distances and orientation measured from the satellite views. This then also helped inform the design of the profile view (side view), as we matched locations of major features visible from the satellite views. We also took into account any photographs we could find. Since, as we mentioned, we could find no overall views, these included the online image of the Soho class helicopter deck with helicopter, and another of a Najin class frigate, that happens to show then “dear leader” Kim Jong-il on the aft deck of what is clearly the Soho. This last view shows some of the rear deckhouse, and was detailed enough to make out some of the features of this deck structure, including the mast and some of the Soviet/Chinese derived radar sets.

And one more time! Soho draft general arrangement : waterline profile and overall deck layout. For all use please credit with a link to this site.

One area of the design we struggled with was the twin bows. We knew from the satellite image that the forward deck tapers conventionally to a broad, rounded point. Many other catamaran designs, such as Dergach missile boats, the Sea Fighter and USN Spearhead Expeditionary Fast Transport have a squared off foredeck that doesn’t project much beyond the stems of the twin-hulls. Other designs, such as the new Iranian catamaran, actually have a cut-back foredeck that sweeps back towards the deck house.

The North Koreans had another large catamaran, also built at Najin shipyards during the 1980s. If possible, even less is known about the submarine rescue ship Kowan, which we do believe we located in views of the submarine base at Chaho. Jane’s Fighting Ships editions feature no views of this larger, 275-foot long vessel, but, fortunately, there is at least one online photo (taken from a collection of ship photos and used on the Korean blog Morning Fog) that seems to show this vessel. We can speculate that the Soho would have had some similarities, including the raked stems.

Casting a wider net, one other vessel inspired our design: the Russian submarine salvage ship Kommuna, a very early naval catamaran which we explored in an earlier post, had a similar broad, rounded bow structure that projected forward of the twin stems.

Additional Resources:

-“New North Korean Helicopter Frigates Spotted” J. Bermudez. The site has good analysis of the Soho, with some of the images discussed above including the Digital Globe view:

Launch of Naj-A Najin Shipyard Number 28 North Korea Feb. 1982:

A 1982 CIA report on the original construction, which included photo interpretation of (still redacted) imagery, released 2011. Naj-A was the original western intelligence designator of the Soho. Since it can be assumed that the redactions contained good aerial or satellite imagery, supporting the description of dimensions and major armament, it should be considered generally accurate.

Missile-equipped combatants Toejo-Dong Naval Base and Missile Support Facility, North Korea (Sanitized) Dec. 1982:

Another CIA report, about the activity of Soho, Najin, and Soju missile-equipped ships. This also makes use of National Photographic Interpretation Center imagery, which is also all still classified and redacted. This report has additional information about the armament of Soho. community thread “North Korean Frigate Soho“, featuring a different reconstructed design, and the 2006 Digital Globe capture with analysis:

* The four STYX missiles (NATO codename) could have been the original Russian P-15 termit units, Chinese developments of these, that had different capabilities, or North Korean-built derivative KN-1 or 01.

The Unknown Warships of the Hermit Kingdom!

Come see satellite views of warships that make you go “huh?” in North Korea!

North Korea has one of the most unusual – and least known – fleets. From antiquated ex-Soviet submarines and patrol boats to advanced-looking catamarans, the Korean People’s Navy (KPN) is the 39th fleet documented in a series of new pages on our project. We are certainly not the only ones gazing at satellite views of North Korea and wondering…what the hell?!

The Shipsearcher Identification Section (SIS) faced more than the usual challenges locating naval units in the scattered East and West Sea naval ports. The extreme lack of photographs of North Korean ships has made interpreting the satellite views a trial. 

Najin North Korea with fleet 2009
Commercial port facilities and the naval shipyards are along the North side of the Bay. In this September 2009 capture, many of the East Sea fleet’s surface units are anchored.

Some of the earliest units transferred to the North, in late 1953, after the active fighting of the Korean War ceased, were elderly Russian minesweepers. These 1930s Fugas/Tral class sweepers/patrol ships inspired the design of the domestically-constructed Sariwon class corvettes. All these years later, 3 Sariwons and 1 of those Stalinist-era Russian ships remain in active service!

This aerial photograph, taken by Japanese military aircraft in the Sea of Japan during 1993, appears to show one of the then 55-year old ex-Russian ships. Though the bow gun is described as an 85mm tank gun off a T-34/85 tank, it looks to us like a larger 100mm Russian or Chinese tank gun. NARA: USN 330-CFD-DN-SC-94-01225
Tral class Munchon 2019
The distinctive differences with what we know of the similar Sariwon class are the twin gun positions in the stern deck, the raised superstructure amidships, on either side of the funnel, and the crescent-shaped flying bridge roof.

The larger Najin class frigates are sometimes described as a near copy of the Russian Kola class. They have formed the mainstay of the surface combatant fleet since four units were built in North Korea starting in the early 1970s. In their lengthy career they were armed with torpedoes, then, in the early 1980s, with cannibalized STYX anti-ship missiles and tubes off missile boats. The two that remain in service are even now being updated – at least one has been seen armed with some version or copy of the modern Russian Kh-35 anti-ship missile.

Najin class corvette or light frigate no. 531 underway, ca. 1993, with the two STYX missile bins fitted between the funnels. NARA: USN 330-CFD-DN-SC-94-01224

For a period in the early 2000s, it looked like the Najins would be joined by a mystery frigate! Around 2004 the unmistakable hull of a comparatively massive Russian Krivak class ship appeared out of nowhere in Nampo shipyards. According to various observers it was an uncompleted Krivak III class ship on the stocks at Mykolaiv, Ukraine. It would have joined sister-ships in the Black Sea fleet in first the Russian, and then the Ukrainian Navy. Somehow, with the likely intercession of a Russian firm, this “dead hulk” got sold to North Korea. Had the ship been completed, it would have become the largest surface unit of the KPN. However, it vanished from Nampo before 2008, and has not reappeared.

krivak frigate Nampo NK 2004
The unfinished Krivak in Nampo. Reports that this was radically altered to become a much shorter modern frigate seem absurd, and it is more likely the hulk was scrapped or sunk.

After the Najin class, large domestically-designed KPN warships became increasingly odd. The most unusual ship was the futuristic Soho helicopter-carrying missile-equipped catamaran of the early 1980s. There are virtually no photos of most spaces on this ship. Its design did seem to inspire a host of follow-on smaller catamarans and surface-effect-vessels. The Nongo class ships started to appear in the early 2000s. There are at least 3 varieties with some major differences – the earliest appears to have a “stealthy” radar reduced cross-section, some are armed with Kh-35 or derivative anti-ship missiles, and they come in a few sizes.

The Nongo class may also be the only craft fast enough to accompany and support another strange feature of the fleet: the numerous Kongbang class assault hovercraft. Should widespread hostilities break out again on the Korean peninsula, the main task of as many as 140 Kongbangs would be to quickly land several thousand special operations troops in South Korean territory – an incursion around the Demilitarized Zone which would be intended to disrupt the South Korean military response.

We hope visitors are interested in our new pages, where we try to arrive at a detailed satellite imagery exploration of the mysterious North Korean fleet!

Tondar hovercraft, Iranian Navy. This craft is similar in appearance to the North Korean units. These both were developed from the same British Hovercraft Corporation / Saunders-Roe design. Credit: Tasnim News Agency, CC BY 4.0 , via Wikimedia Commons
Kongbang class hovercraft are staged near the borders in several locations, seemingly poised to descend on the South Korean coast.

Additional Resources:

A declassified Central Intelligence Agency report on the North Korean Navy in 1986, with a summary of all warship types in service and in construction in that era:

To see views of the technologically-advanced, highly capable South Korean fleet, which would oppose North Korean naval operations in a future conflict, check out our pages for the Republic of Korea Navy.

The variations in types within the Nongo class fast attack craft are analyzed by HI Sutton, on his site, Covert Shores.

A National Post Apr. 2014 article “Graphic: North Korea’s Conventional Arms” by Richard Johnson, Andrew Barr, and Jonathon Rivait has a summary of naval units and silhouette views of KPN ships/boats and submarines: . There appear to be a few inaccuracies, such as the Kowan class ASR sub rescue vessel (which looks like a much older trawler or tug-based sub rescue vessel), but it is an interesting attempt to visualize the fleet, and helps highlight the distinctive differences in these very similar types.

In several ways, the unusual warships we located reminded us of the Iranian Navy, which we explored earlier in pages and posts. There has been some technology transfer between these two, and the mix of fast attack craft, midget submarines, light frigates and corvettes is similar.

Stay tuned for an upcoming blog post where we explore features and attempt to reconstruct views of the mysterious and highly unusual Soho missile-equipped, helicopter-carrying catamaran frigate!