South Korea has not yet taken a concrete stance on whether it will accept THAAD deployments. There are several reasons for this posture. First, according to South Korean officials, the United States has not yet issued a formal request to deploy the system, meaning that there have been no consultations. This is technically true but South Korea and others have known for years that the United States considers Korea a prime location for THAAD deployment. Reports in South Korean media said that the U.S. military had already assessed potential sites in South Korea — a fact Seoul is aware of.
Seoul's second reason for remaining noncommittal stems from concern about maintaining its balance between the United States and China. While the United States is South Korea's most significant defense partner, China is South Korea's largest trading partner. Seoul has also worked for years to use its political ties with Beijing to help manage the North Korean threat. As North Korea's largest trading partner as well as its main economic and security patron, China is in a singular position to assist South Korea in its relationship with North Korea.
Risks of Deployment
THAAD deployment — as seen vividly in Beijing's public objections — carries immediate political risks for South Korea. The question is whether the benefits of deployment outweigh those risks. Authorizing the deployment of THAAD would increase the robustness of South Korea's layered missile defense system. THAAD would protect against tactical and theater ballistic missiles, at ranges up to 200 kilometers (125 miles) and altitudes up to 150 kilometers (93 miles). A THAAD battery, typically composed of nine transporter or launcher vehicles with eight missiles each, two mobile tactical operations centers and a ground-based X-band radar, also uses a "kinetic kill" system. The system does not employ explosive warheads and can intercept hostile ballistic missiles inside or outside the earth's atmosphere.
But South Korea's defense system also includes Patriot PAC-3 systems for point defense and Aegis-equipped destroyers as the initial source of interceptors to knock out ballistic missiles during their mid-course flight. The PAC-3 system has proven itself capable of intercepting less advanced Scud missiles. Practically, the systems in place may be enough to protect South Korea — in a time of war many of North Korea's longer-range missiles would likely target U.S. bases in Japan. This is not to minimize the ballistic missile threat from North Korea. For Seoul, however, there are reasons to consider different air defense architecture. This architecture would deal with the full range of the threat from North Korea while giving South Korea a degree of operational independence and a freer hand in designing its own defenses.
Over the past decade, South Korea has sought to create a defense architecture that is more independent of the United States. Seoul is not necessarily looking to expel U.S. forces from the country but it cannot be sure that U.S. interests will always align with those of South Korea. Seoul also finds it politically fraught to be entirely dependent upon the United States for its defense. Washington has pressured Seoul to tighten defense ties with Japan — a move that many South Koreans oppose for historical reasons.
The United States has also been pushing for changes in the defense alliance architecture that would allow U.S. forces in South Korea to deploy elsewhere in times of crisis. Seoul fears that granting the United States this option would ultimately lead to South Korea being tied politically to any overseas U.S. war. Finally, South Korea is concerned that the United States is overly cautious about Chinese concerns to the detriment of South Korean interests. Seoul was frustrated by the long delay in a U.S. show of naval force off South Korea's coast following the March 2010 sinking of the ROKS Cheonan, allegedly by North Korean torpedoes.
Seeking More Independence
In addition to these strategic concerns, Seoul would like to boost its own domestic defense industry for economic reasons and technological development. It would also wean South Korea off of its dependence on the United States for supplies and defense. Seoul already invested money toward its own air defense network called the Korea Air Missile Defense, a series of systems that would include U.S. elements but not be completely tied into the U.S.-Japanese anti-ballistic missile architecture. The system would free up Seoul to pursue missile and anti-missile development projects with Israel or even Russia.
Washington has long hesitated to more fully share missile development technology with South Korea — a stance that has been a bone of contention between the two allies. The United States argues that reliance on U.S. systems preserves the balance of power because it reduces South Korea's ability to unilaterally begin a war with North Korea. While THAAD would bolster South Korea's immediate defense — or at least the defense of U.S. bases in South Korea — it would do little to improve South Korea's ability to develop its own systems or expand its own defense industry.
The South Korean debate over THAAD deployment has become highly public — something that Seoul never intended to happen. Managing the U.S. defense relationship has been a controversial topic in domestic politics with South Korean political parties expressing competing views. Though the government in Seoul — whether conservative or liberal — largely agrees that South Korea must maintain a robust defense alliance with the United States, the exact balance and level of self-determination are both hotly contested. Even before the introduction of the question of political risk to Chinese relations, the THAAD decision was subject to competition within Seoul.
However, China's decision to so actively and publicly decry a deployment that has yet to be officially requested has forced Seoul to openly and immediately address the issue. It has also pushed Seoul toward approving at least a limited THAAD deployment on the Korean Peninsula — if only to underscore the independence of its decision-making.
Editor's Note: This is the first of two analyses on THAAD deployment in South Korea, read the second part here.