South Korea’s US-Built Nuclear Submarine Will Likely Lead To Seoul Joining AUKUS+

Its role might remain limited to Chinese missile and submarine tracking via THAAD and its upcoming nuclear sub respectively, but this would still be of great assistance to its allies in the event of a crisis.

One of the highlights from Trump’s latest tour of Asia apart from the Thai-Cambodian Peace Accords that he brokered and his meeting with Chinese President Xi Jinping was the announcement that the US will build South Korea’s first nuclear submarine. This represents the second recent instance of the US sharing this highly guarded military technology after the creation of AUKUS in September 2021. This refers to the trilateral pact between Australia, the UK, and the US for building Australia’s first nuclear submarine fleet.

AUKUS is considered to be the core of a NATO-like alliance in Asia aimed at more robustly containing China through increased “burden-sharing” in pursuit of this shared strategic goal. Japan, the Philippines, and Taiwan, all three of which are American allies (the first two being the US’ mutual defense allies while the US’ responsibility to the last is deliberately ambiguous) and can collectively be referred it as the “Asian/Containment Crescent” vis-à-vis China, are accordingly regarded as members of AUKUS+.

This refers to the informal expansion of AUKUS beyond its three founding members, the American one of which is indisputably the core just like with NATO, and South Korea is naturally expected to join AUKUS+ once the US finishes building its first nuclear submarine. While the implied pretext for this privileged military-strategic cooperation between them is containing North Korea, which allegedly has its own nuclear submarine and reportedly received Russian reactor technology too, the real target is China.

South Korea adroitly balances between China and the US, the first of which is its top trade partner and practically is neighbor while the latter is its top security partner tasked with defending it from the scenario (however far-fetched) of another North Korean invasion, but it leans closer to the US than to China. While it’s unlikely to get directly involved in any Sino-US crisis over Taiwan, such as if China resorts to forcible means for reuniting with its rogue province, its nuclear sub can still monitor Chinese ones.

Japan via the Ryukyu Islands and the Philippines via Luzon Island, both of which host US bases, could play logistical support roles in that scenario or even directly engage Chinese forces from there. By then, it’s also possible that Japan might have already developed its own nuclear weapons via an accelerated program that exploits its huge plutonium stockpile to this end while the UK might transfer some of its submarine-launched nukes to Australia for use in its new nuclear subs, both with American approval.

The trigger for such escalations would be if China reciprocally tests nukes in the event that the US does so first like Trump recently authorized (though it’s unclear whether this will happen), in which case Japan could rapidly develop nukes while Australia wouldn’t get UK ones till its subs are built in the next decade. Prior to then, however, Australia is already expected to host allegedly conventionally armed American and British nuclear subs on rotation by 2027 that might officially become nuclear-armed in that scenario.

The importance of the preceding two paragraphs is to contextualize South Korea’s role in AUKUS+, which will likely remain supplementary and less direct than its allies’, with the only focus being on Chinese missile and submarine tracking via THAAD and its US-built nuclear sub respectively. These are still important roles, however, and could expand to other domains one day too. The only thing preventing that, at least for now, is South Korea’s fear of an asymmetrical economic response from China.