National Interest

by James Holmes

    Many countries want nuclear submarines for national prestige rather than for security needs. But South Korea is well-positioned to use them effectively.

    I confess I did not have South Korea builds a nuclear-powered submarine with American help on my bingo card for 2025. Yet so it is, apparently. On October 29, President Donald Trump announced that in exchange for tariff relief and an agreement to purchase hydrocarbons from the United States: “I have given [Seoul] approval to build a Nuclear Powered Submarine, rather than the old fashioned and far less nimble, diesel powered Submarines that they have now.” The announcement welcomed South Korea to an exclusive club of recipients of US nuclear propulsion technology—enriched uranium fuel in particular—alongside the United Kingdom and Australia.

• Diesel Subs Aren’t as Good as Nuclear Ones—but They’re Usually Good Enough

    Of course, Trump overstated the advantages of nuclear-powered submarines over their conventionally powered brethren. Wise naval commanders pick the best tool for the job and the best tool need not embody the latest über-pricey naval technology. It all depends on the operational and tactical setting as well as the capability of likely foes. Old tech can be good tech. Or, more accurately, it can be good enough—which amounts to the same thing in martial affairs. Excess capability is waste.

    The commander-in-chief himself appears to understand this notion well. He has gone on record touting battleships or their descendants—old-fashioned behemoths by any standard—as mainstays of future surface warfare. He has also advocated retrofitting steam-driven catapults aboard US Navy aircraft carriers. Trump seems to envision replacing the ultramodern electromagnetic launch and recovery systems found in the Gerald R. Ford-class carriers, the latest in the breed, with antiquarian steam technology whose origins lie in the 1950s.

    The principle that old can be good reigns beneath the waves as well. In many cases, old-fashioned diesel-electric submarines (SSKs), which have been around in one form or another for well over a century, are adequate unto the times and surroundings. The Japan Maritime Self-Defense Force used SSKs to great effect during the Cold War, dispatching them to monitor and, if necessary, interdict Soviet or Chinese shipping in straits along the first island chain. Japanese boats have resumed access-denial operations in this age of a domineering China.

    In other words, diesel boats often suffice for the times and circumstances. SSKs are cheap enough relative to nuclear-powered attack submarines (SSNs) for a navy on a budget can afford several of them for the price of one SSN.

    Quantity has a quality of its own. A numbers-rich fleet lets commanders scatter assets across the nautical chart to cover more geographic space, or operate wolfpacks against enemy fleets. SSKs boast enough firepower to do the job against surface shipping and land targets. They have enough operating range to reach nearby patrol grounds and linger there. They run silent enough to elude acoustic detection. And the latest diesel boats, fitted with air-independent propulsion, command enough staying power to remain submerged for several weeks without snorkeling in order to dodge surface-skimming or airborne sub hunters. These are not traits to sniff at.

• South Korea Could Use Nuclear-Powered Submarines, Too

    Still, like other SSN operators, Seoul would derive considerable advantage from adding atomic propulsion to the mix. First, while SSKs mainly hunt surface vessels or bombard sites on shore, SSNs boast the speed to hunt fellow submarines. The all-nuclear US Navy silent service regards the best submarine-killer as another submarine. Republic of Korea Navy (ROKN) SSNs would be well suited to counter the rival Korean People’s Navy submarine fleet. The North Korean contingent ranks among the world’s largest subsurface forces—albeit of doubtful quality—and now operates two nuclear-powered ballistic-missile submarines (SSBNs). ROKN SSNs would constitute a natural complement to antisubmarine forces riding the sea’s surface or aloft.

    Second, naval nuclear propulsion extends an SSN’s seakeeping ability far beyond that of even the most advanced conventional attack boat. The only real limit on a nuclear-powered boat’s undersea time is food and related stores for the crew. For instance, US Navy SSBNs lose themselves in the depths on 77-day patrols. There are enough boats in the inventory to keep multiple “boomers” at sea at all times, reinforcing nuclear deterrence. Once the ROKN constructs enough SSNs, it will likewise be able to maintain a permanent, rotating, largely undetectable presence in waters adjoining the Korean Peninsula. A standing presence will cast a shadow across policy and strategy deliberations in Pyongyang—potentially inducing new restraint within Kim Jong-un’s regime.

    And third, an SSN contingent would expand the ROKN’s operating radius, opening up new strategic and political vistas for South Korea. While North Korea will remain Seoul’s top priority barring the fall of the Kim regime, operations elsewhere in the Indo-Pacific would become thinkable. Forging a grand consortium with the AUKUS navies, all of which will operate nuclear-propelled submarines in the coming years, would be one natural possibility. In short, adding an SSN contingent to the ROKN fleet would generate novel options for South Korean leadership in maritime Asia—and perhaps beyond.

    Over two millennia ago, according to the Greek historian Thucydides, an Athenian delegation proclaimed that “three of the strongest motives” that impel societies and individuals are “fear, honor and interest.” Classicists quibble about the order in which Thucydides lists these motives, but this ranking seems fitting to explain South Korea’s quest for nuclear-powered attack subs. Staving off fear of North Korean aggression, which poses a mortal threat, must come first in any South Korean military strategy. Holding fear at bay buttresses national honor and in turn the credibility of Seoul’s efforts at deterrence. And any interest in regional leadership depends on acquiring longer-range ships of war. Ships like SSNs.

    Naval nuclear propulsion for Korea  Endorsed. Now do Japan!