By: Emma Kim
As the US focuses its attention on the ongoing war in Iran, South Korean doubts regarding the reliability of US nuclear deterrence grow. If the US hopes to prevent nuclear proliferation, it needs to reassure its essential ally, South Korea, that its protection is still at the forefront of US policymakers’ minds.
South Korea has long relied on its status as one of the nations under the US’s nuclear umbrella to deter attacks from neighboring North Korea, but with increased US involvement in other conflicts worldwide, support for a home-grown nuclear weapons program in South Korea increases.
Sitting US president Donald Trump has been somewhat ambiguous regarding his stance on South Korean nuclear proliferation. Comments made during his first presidency in 2016 implied that American troops stationed in South Korea as a deterrent tripwire force to prevent outright attacks from North Korea were not guaranteed to remain there. Although these comments did not ultimately lead to a withdrawal of US troops, they signified Trump’s willingness to place the burden of deterrence on South Korea, heightening the likelihood that they could feel compelled to develop their own nuclear weapons.
Domestic support of developing nuclear weaponry has been present in South Korea for many years, with surveys indicating approval ratings of 50-60% with steady increases as time passes. Even prior to the war in Iran, a 2025 survey indicated a record high 76.2% support for an indigenous nuclear weapons program.
Following the US’s involvement in Iran, diplomatic and military focus has been directed away from the two Koreas and Asia at large. Components of the Terminal High-Altitude Area Defense (THAAD), which serves as an important component of South Korea's anti-missile defense system, are currently being moved to Middle Eastern sites (hyperlink source). These actions from the US have only reinforced doubts regarding the Trump administration's commitment to the Korean peninsula.
Concerns regarding South Korean proliferation are especially salient considering South Korea's existing civilian infrastructure for nuclear power. The US has long supported South Korean nuclear energy with the caveat that enrichment can’t happen without US approval, but as South Korea has grown into one of the world's largest nuclear power producers with 26 reactors currently in operation and three more currently under construction, the transition to nuclear weapons production is increasingly feasible.
In addition to these comments, a more recent example of Trump’s ambiguity can be found in the US’s November 2025 decision to support South Korea adding nuclear-powered submarines to their military arsenal. While these submarines would not be equipped with nuclear warheads, they present South Korea with the technology to deliver nuclear warheads should they be developed. South Korea has already developed ballistic missiles with the capability to deliver nuclear warheads, and securing further delivery systems may make proliferation more feasible.
Besides concerns of abandonment as the US is drawn into conflicts overseas, South Korea and other US allies must also confront the possibility of entrapment into a war which they did not initiate. If South Korea is reliant on the US to provide deterrent nuclear threats in its name, the US may be able to leverage that dependency and draw South Korea into external conflicts. There has already been an instance of the US calling upon South Korea to send forces to the Strait of Hormuz in an attempt to secure it against Iranian attacks, highlighting these concerns. If South Korea possessed nuclear weapons of their own, they may be less susceptible to pressure from the US.
With all of these considerations in mind, it is important for the US to draw a clear line regarding South Korean proliferation and in turn make security guarantees to reassure South Korea. While proliferation from a fellow democratic nation may not seem to pose a great threat to global security, it could cause a ripple effect resulting in other East Asian countries arming themselves with nuclear weapons.
It is important that South Korea is not forgotten in this moment of global conflict, as their technological advancement, high military budget, and increasing domestic support all prime them to become a nuclear state.
