Following the visit of United States President Donald Trump to South Korea on October 29, 2025, the parties announced that they would advance their partnerships in shipbuilding, artificial intelligence, and the nuclear industry, and that they would build nuclear-powered submarines within this scope.[i] Under the agreement, the US pledged to support South Korea’s nuclear-powered submarine production, while South Korea promised to invest USD 150 billion in the US shipbuilding sector and USD 200 billion in the industrial sector.[ii]
Not long before this agreement, Washington agreed to lower its trade tariffs on South Korean goods from 25 percent to 15 percent. In doing so, the Seoul administration achieved a significant agreement to counter Pyongyang’s dangerously escalating military capabilities. Indeed, North Korea had recently announced that it had begun production of nuclear-powered submarines. Therefore, the US is keen to preserve the military balance between the Koreas. In order to counter potential nuclear attacks by North Korea, South Korea announced plans to conduct joint nuclear exercises with the US in recent years, but this has not been followed through.[iii]
As far as South Korea is concerned, possessing nuclear-powered submarines would give Seoul a considerable advantage in the strategic balance of power in the Asia-Pacific region. As a matter of fact, submarines equipped with this technology can be found in the inventories of only six countries. These are the United States, China, Russia, the United Kingdom, France, and India. Additionally, Australia signed a cooperation agreement with the United Kingdom and the United States in 2021 regarding the production of nuclear-powered submarines. The balance of power in the Asia-Pacific region rapidly shifted with this agreement, known as AUKUS.
The advantage of nuclear-powered submarines over others is that they tend to stay underwater longer and are associated with the distance they cover. As nuclear technology is difficult to obtain and costly to develop, many other countries have opted for diesel-electric submarines. It can therefore be said that nuclear submarines are generally owned by major powers or developed by advanced countries (medium-sized powers) with ocean fronts that are more willing to develop this technology. For instance, India has mostly leased or purchased nuclear-powered submarines from Russia, and has managed to produce nuclear submarines with Russia’s assistance over the past 15 years.
Another important point to be emphasized here is that submarines can also be categorized based on their drive systems or armament patterns. In this regard, the South Korean example refers to submarines being nuclear-powered. Otherwise, some submarines may be armed with, say, ballistic missile systems that are capable of carrying nuclear warheads, and these are mostly defined as “Tactical Nuclear Attack Submarines.” When viewed through this perspective, North Korea accomplished the production of its first tactical nuclear attack submarine, named “Hero Kim Kun Ok,” in 2023. Again, when viewed through this perspective, it is evident that South Korea does not possess a submarine in the same category.
The latest agreement between South Korea and the US prompted an immediate response from North Korea, with the Pyongyang administration warning that the deal could trigger an international arms race by creating a “nuclear domino effect” in the region.[iv] In the mid-to-long term, this agreement could become a useful argument for Pyongyang to expand its own nuclear program. North Korea, which has mentioned South Korea’s “secret nuclear armament ambitions,”[v] could use this as a justification to pursue the development of its own nuclear strike capabilities. This arms race and the deterioration of the security environment have the potential to shape not only the future of the Korean Peninsula but also that of the Asia-Pacific region as well as the world. The partnerships that Japan and South Korea have established with the US over the defense sector are indirectly leading to a confrontation in the region, that is, to the formation of new blocs. Hence, various analysts suggest that the US Asia-Pacific strategy is being redesigned to be South Korea-centered.[vi] According to this configuration, allies such as Japan, South Korea, Australia, and India stand alongside the United States, while actors such as China, Russia, and North Korea are positioned in the opposing bloc.
Yet, China constantly highlights the negative effects of this bloc-building policy and calls on regional states to distance themselves from such policies. After all, tensions on the Korean Peninsula pose the greatest threat to the security of neighboring countries such as China and Japan. Thus, China stands out as an actor concerned about North Korea’s dangerous missile tests and military exercises, calling for a departure from the Cold War mentality. On the other hand, South Korea and Japan continue to develop their military forces due to the constantly deteriorating security environment and the risk of probable conflict. Despite this, South Korea pursues a more cautious policy than Japan regarding the possible negative consequences of the US’s increasing presence in the Asia-Pacific. This cautious stance is more pronounced in relations with China. In other words, the Seoul administration is concerned that its growing ties with Washington will significantly damage its relations with Beijing. Similar fears are by no means as prevalent in Tokyo.
In conclusion, it can be suggested that efforts to denuclearize the Korean Peninsula have regressed further and that a “balance of terror” similar to that of the Cold War era has begun to emerge in the region. Although nuclear-powered ships are different in nature from nuclear submarines capable of carrying nuclear warheads, they ultimately involve the use and proliferation of nuclear technology. Countries that possess technologies such as uranium enrichment, after reaching a certain level, are also capable of producing nuclear weapons. The spread of these capabilities to Asia-Pacific countries could potentially undermine global efforts to rid the world of nuclear weapons. The use or securitization of nuclear technology for security purposes may be one of the most significant debates in the coming years.
[i] “The US will help South Korea build nuclear ‘attack’ submarines – here’s what that means”, BBC,https://www.bbc.com/news/articles/c620qppzlgwo, (Access Date: 18.11.2025).
[ii] “US, South Korea to ‘move forward’ on building nuclear-powered submarines”, Al Jazeera, https://www.aljazeera.com/news/2025/11/14/us-south-korea-to-move-forward-on-building-nuclear-powered-submarines, (Access Date: 18.11.2025).
[iii] “South Korea Says Talks Underway On U.S. Nuclear Operations Planning”, Nikkie, https://asia.nikkei.com/Spotlight/N-Korea-at-crossroads/South-Korea-says-talks-underway-on-U.S.-nuclear-operations-planning, (Access Date: 18.11.2025).
[iv] “North Korea says US-South Korea deal to set off ‘nuclear domino’ effect”, Reuters, https://www.reuters.com/world/asia-pacific/north-korea-says-us-south-korea-fact-sheet-shows-confrontational-stance-2025-11-17/, (Access Date: 18.11.2025).
[v] ibid.
[vi] “US commander’s new map repositions S. Korea at heart of regional strategy”, Korea Times, https://www.koreatimes.co.kr/southkorea/defense/20251117/us-commanders-new-map-repositions-s-korea-at-heart-of-regional-strategy, (Access Date: 18.11.2025).
