That Time the U.S. Navy Sank a Fake, Yellow, North Korean Submarine

What appears to be an authentic North Korean midget submarine was actually a training target.

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National Archives

A series of newly surfaced photos recently caused a flurry on social media as they appeared to show an actual North Korean midget submarine in the hands of the U.S. Navy. In fact, the submarine was a target built for torpedo practice, but it was towed off the coast of California where it was sunk.

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National Archives

The photographs are dated to 2004 but only recently surfaced on social media, depicting a submarine that looks exactly like a Korean People’s Navy Sang-O (“Shark”) class midget submarine towed by a tugboat with a pair of divers on deck. According to the U.S. National Archives where the (,) are hosted, the object is a real diesel electric submarine. The divers are preparing to close a pair of shut-off valves “to partially sink a submarine for use as a target for torpedo launches. The submarine is of the same size and length as diesel submarines used by several countries.”

While some viewers took the sub to be genuine, research associate for Defence & Military Analysis at the International Institute of Strategic Studies Joseph Dempsey stated on Twitter that the object was actually a Weapon Set-To-hit Threat Target (WSTTT).

I'm guessing the resemblance between torpedo "set-to-hit" test platform and a Sang-O class coastal submarine is not purely coincidental.

— Joseph Dempsey (@JosephHDempsey)

A little digging reveals Dempsey was of course correct. The “North Korean submarine” is the WSTTT and , which includes a brief explanation:

Weapon Set-To-hit Threat Target (WSTTT) was developed in San Diego to support Operational Test and Evaluation Force (OPTEVFOR) operations used to test Anti-Submarine Warfare (ASW) sensors and weapons. It can be lowered and raised from a surface support platform, but has no dedicated propulsion system. The platform allows unarmed ASW torpedoes to impact the vessel without any explosion.

The National Archives captions were not entirely correct. The WSTTT was not a “diesel submarine”—the target had no diesel engine, although the submarine description was debatably true.

Why would the U.S. Navy train against such small submarines? Although just 115 feet long, the Sang-O class is more or less North Korea’s frontline submarine. Each Sang-O has two 533-millimeter torpedo tubes to carry heavyweight anti-ship or anti-submarine torpedoes. As submarine authority H.I. Sutton, author of the submarine website, points out, “North Korea's midget submarines still pose a serious threat to surface ships, as the . That warship was cut in half by a North Korean torpedo in 2010. The submarine which launched it was roughly similar to the Sang-O.”

Although the WSTTT was clearly designed to look like a Sang-O submarine, this ship was definitely made in the United States.

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