Some political figures in South Korea and Japan are feeling extremely uneasy as North Korea steps up its missile and nuclear tests. The Moon Jae-in government has not only deployed the US Terminal High Altitude Area Defense (THAAD) missile interception system, but is also mulling the deployment of US tactical nuclear weapons in South Korea.
This plan started from the previous Park Geun-hye administration. Although the South Korean government holds reservations about developing and introducing nuclear weapons from the US because of public opposition and legal restrictions, top security officials of the Park government have held informal talks in this regard, and communicated with the US.
However, high-ranking security officials of the new government still remain open in terms of the introduction and development of nuclear weapons after Moon took power.
South Korean Defense Minister Song Young-moo visited the US last month to hold talks on nuclear weapons. Although President Moon claimed the talks were not held with the agenda to bring back tactical nuclear weapons from the US, it is clear that the new government has made attempts to do so.
Seoul is facing hardships as missile and nuclear programs in Pyongyang almost spiral out of control. Despite the US nuclear umbrella, South Korea must have its own nuclear deterrence to confront North Korea if the US goes back on its words.
However, for a long time, the US does not allow its non-nuclear allies to develop nuclear weapons. Hence, top security officials of the Moon administration may use their position of not developing nuclear weapons as a bargaining chip for demanding more assurance from the US on the Seoul-Washington alliance, which can be achieved through the installation of tactical nuclear weapons on their soil.
The deployment of nuclear weapons in South Korea will only exert symbolic impact on North Korea. More flexible plans lie ahead if the US considers hitting North Korea with nuclear weapons, such as using those deployed outside the Korean Peninsula to intimidate Pyongyang.
The introduction of US nuclear weapons in South Korea does more harm than good. The US has given high priority to avoid the worldwide proliferation of nuclear weapons after the Cold War. In 1992, the US government decided to withdraw tactical nuclear weapons from foreign countries, including South Korea, to demonstrate it would be less reliant on nuclear weapons in its national security strategy.
The US also asked other nations to follow suit in that nuclear states should mitigate their dependence on atomic armaments, and non-nuclear nations should keep their promise of stopping the development of such systems.
Therefore, US efforts to thwart the expansion of nuclear weapons after the Cold War will likely count for nothing if the arsenal is reintroduced on South Korean soil.
Seoul and Pyongyang signed the Joint Declaration on the Denuclearization of the Korean Peninsula in late 1991. Both sides agreed not to "test, manufacture, produce, receive, possess, store, deploy or use nuclear weapons." Although North Korea violated the declaration, the US and South Korea can still require North Korea to stick to its words via the joint declaration and relevant statements issued by the Six-Party Talks on the denuclearization of the Korean Peninsula.
Once US tactical nuclear weapons are deployed on the peninsula, Seoul will break its promise of denuclearization and hence will have no moral ground to ask North Korea to stop nuclear tests.
Although the barrier to installing US nuclear weapons in South Korea remains huge, Washington agreed to remove limits on the payload of South Korea's ballistic missiles to give comfort to its ally.
As the Trump administration shows a withering stance toward the US alliance system, how the US handles its security relations with Japan and South Korea merits close scrutiny.
The author is deputy dean of the Institute of International Studies at Fudan University.