Why South Korea agreed to deploy US missile-defense system

After years of speculation and contemplation, South Korea and the United States have finally agreed to go ahead and deploy THAAD, an advanced missile-defense system.

An advanced US missile-defense system capable of intercepting short- and medium-range ballistic missiles is to be deployed in South Korea, officials announced Thursday, after years of hesitation in the face of Chinese push-back. 

The Terminal High Altitude Area Defense (THAAD) is something the United States has long been touting, arguing that it is a sensible precaution against North Korea's missiles. South Korea, however, has been hesitant to move ahead, wary of risking Chinese cooperation to rein in North Korea's missile and nuclear programs.

A recent flurry of missile tests and a nuclear detonation by Pyonyang, however, have brought a sense of urgency to the situation and precipitated intense consultation this year between Seoul and Washington.

In a joint announcement Thursday, the Republic of Korea and the US declared their intention to “ensure the swift deployment of THAAD,” drawing quick condemnation from both China and Russia.

“North Korea's nuclear test and multiple ballistic missile tests, including the recent intermediate-range ballistic missile (IRBM) launches, highlight the grave threat that North Korea poses to the security and stability of the Republic of Korea (ROK) and the entire Asia-Pacific region,” reads the statement.

In a tacit acknowledgment of China’s concerns, the statement goes on to say the missile-defense system would focus “solely on North Korean nuclear and missile threats and would not be directed towards any third party nations.”

Nonetheless, the Chinese foreign ministry expressed dismay, saying it is "strongly dissatisfied with and firmly opposes [sic] to" the forthcoming deployment, which the ministry suggested would hinder denuclearization of the Korean peninsula.

Beijing’s concerns over the system stem from a belief not so much that it would be able to bring down Chinese missiles, but more that it might provide early warning “in the fantastic and highly unlikely event of a nuclear confrontation” between China and the United States, as Nicholas Kitchen of the London School of Economics and Political Science told The Christian Science Monitor earlier this year.

In fact, the Chinese find the prospect of THAAD so disconcerting that one South Korean diplomat suggested that, should it be deployed, “it would destroy our bilateral relationship with China in an instant," according to Dr. Kitchen. 

Russia’s foreign ministry, too, has expressed its dissatisfaction with the decision, suggesting that the deployment will “very negatively affect global strategic security,” and saying it could escalate tensions in the region.

None of these reactions likely comes as a surprise to the South Koreans or the United States, but Pyongyang’s recent efforts have included the test-firing of mid-range ballistic missiles, capable of striking US facilities in Guam and Japan. Indeed, North Korea claims to have also tested a missile with the potential to threaten the continental United States.

With these increasing ambitions and capabilities, analysts agree that the thinking in Seoul was finally tipped in favor of taking action, in spite of the likely impact on relations with Beijing.

"If China wanted to exert a lot of influence on somebody to prevent THAAD from being considered going into Korea,” Adm. Harry Harris, commander of US forces in the Pacific, told reporters in February, “then they should exert that influence on North Korea."