This KCNA image purports to show Kim Jong-un attending a sub launch in 2016. Photo: KCNA

The date is June 2022. A gunmetal gray nuclear submarine sits silently on the ocean floor, 100 kilometers off North Korea’s Mayang-Do Naval Base at Sinpo, in the Sea of Japan.

The South Korean hunter-killer submarine, built with US help, has been submerged for six months. It’s playing cat-and-mouse with communist corvettes that ping the bottom with sonar arrays. As night falls, shrouding the area from US spy satellites, a big North Korean Sinpo-E ballistic missile sub with nuclear warheads steals out of Mayang. War is erupting on the Korean peninsula.

The cigar-shaped South Korean sub rises quickly and closes with its target at high speed. It opens a bow door and fires a single US Mk 48 torpedo that obliterates the North Korean sub and its six missiles aimed at Gwangju, Busan, Daegu and other cities.

That, at least, is the scenario imagined by South Korean military planners who intend to build nuclear-powered subs with US help to counter the threat from North Korea. The ambitious submarine-building program was reportedly discussed between Donald Trump and South Korean President Moon Jae-in during the US president’s November visit to Seoul.

The South wants hunter-killer nuclear subs because it believes such vessels offer a stronger deterrent to a sub-based nuclear attack from the North. Reports indicate the vessels will be built in South Korean shipyards but based on US designs and technology. It’s unclear if they’ll resemble Los Angeles-class fast attack submarines or other US types.

Some analysts are skeptical of Seoul’s plan. “I don’t see the strategic rationale,” Asian defense expert Richard Bitzinger told Asia Times. He says South Korea’s Navy would be better served by small, shallow-water diesel-electric subs rather than big nuke boats, if they want to take out North Korean missile subs and ships in coastal waters.

Bitzinger is a senior fellow and coordinator of the Military Transformations Program at the S. Rajaratnam School of International Studies in Singapore.

South Korea’s Navy currently maintains a force of 15 diesel-powered submarines.

Underwater edge

Backers of the South Korean plan note that nuke subs are faster, stay submerged for longer periods than diesel-electric counterparts and are highly maneuverable. On paper, this makes it easier for them to lie in wait for North Korean submarines slipping from their bases to launch missile attacks on the South and its allies.

Seoul also wants the new subs to incorporate indigenous technology. The Korea Times quoted defense officials as saying in October that the country has its own design for a nuclear reactor that can power a 4,000-ton submarine.

Bitzinger says it’s possible for South Korea to design and build indigenous sub reactors, but notes the process could take anywhere from three to five years. He also notes that Brazil and India took decades to develop small nuclear reactors for naval purposes.

Six nations currently have nuclear-powered strategic submarines: the US, Russia, France, the UK, China, and India. Brazil and Argentina also plan to launch nuke subs.

Export-control obstacle

Bitzinger sees a big political hurdle if South Korea tries to get nuke sub technology from the US, however. Though Washington and Seoul have “agreed in principle” to let South Korea build nuclear-power subs, the respected defense analyst says: “I doubt very much if the US would permit the export of nuclear technology to ROK.”

He notes that all aspects of US submarine-building, including nuclear technology, are strictly export-controlled. In the past, Bitzinger says, this has halted the export of non-nuclear features like US sub-hull designs to countries like Taiwan. “Maybe Trump, in his usual kick-over-the-coffee-table manner, could order the export (of such technology) but it would meet a lot of resistance.”

At the same time, it’s likely the US will bolster South Korea’s sub-fighting capabilities by aiding in the construction of new submarines or sharing US anti-submarine warfare technology.

Local newspaper Maeil Business cited a South Korean military source as saying earlier this year that the US Terminal High Altitude Area Defense (THAAD) anti-missile system deployed inside the country is focused on North Korean land-based missiles and would have trouble detecting sub-launched attacks. The same was said to be true of existing South Korean early-warning radar systems.

Submarine-based missiles also allow the North to retaliate even if its land-based nuke-missile launchers are destroyed by US and South Korean forces.

Adding new hunter-killer subs of some type to South Korea’s Navy may well prove viable as part of a layered defense strategy against Pyongyang.

Doug Tsuruoka is Editor-at-Large of Asia Times

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