The Necessity for THAAD in South Korea

North Korea's test launch of an ICBM that could target the United States within the next few years has fixated attention on how Washington and its allies should respond to the growing military threat. However, Pyongyang's nuclear and missile capabilities are already an existential threat to South Korea and Japan. Given these circumstances, the United States and its allies must deploy sufficient defenses to deter and defend against the growing North Korean missile and nuclear threats. Shortly after assuming power in late 2011, Kim Jong-un directed the creation of a new war plan to complete an invasion of South Korea within a week using nuclear weapons and missiles. A senior North Korean military defector indicated that the North’s strategy would be to quickly occupy the entire South Korean territory before U.S. reinforcements would be able to arrive.

In 2016, the regime conducted several successful No Dong medium-range missile tests. North Korean state-controlled media announced that the missile launches were practice drills for preemptive airburst nuclear attacks on South Korean ports and airfields, where U.S. reinforcement personnel would arrive during a military crisis. A North Korean media-released photo showed that the missile’s range would encompass all of South Korea, including the port of Busan—a critical site for transiting U.S. reinforcements.

Pyongyang has repeatedly vowed, including in my meetings with North Korean officials in June 2017, that it will never abandon its nuclear arsenal and has rejected denuclearization negotiations. The Trump administration, for its part, has promised to increase pressure on the regime, strengthen the U.S. military, and increase deterrence and defense through augmented ballistic missile defense (BMD) capabilities. With regards to BMD capabilities, the most immediate upgrade should be to deploy the Terminal High Altitude Area Defense (THAAD) ballistic missile defense system to South Korea.

In conjunction with the already-deployed Patriot missile system, THAAD would create an essential, multilayered defensive shield for South Korea. THAAD is better than any system South Korea has or will have for decades. The Patriot system only has a 30 km altitude and 35 km range capacity, compared to the 150 km altitude and 200 km range of THAAD. Seoul’s planned indigenous long-range surface-to-air missile system would only have a 60 km altitude and 150 km range—both less capable than THAAD—and would not be available for deployment until at least 2023.

China continues to argue that THAAD deployment runs counter to Chinese security interests. This, of course, overlooks the fact that North Korea’s development of nuclear weapons and missiles—and the repeated threats to use them—is contrary to South Korean and U.S. security interests as well. Beijing asserts that the associated X-band radar would be able to peer deep into China to observe military activity and ICBMs targeting the United States during a conflict. However, Beijing's claims are false and disingenuous. Accordingly, China has refused repeated U.S. and South Korean offers of technical briefings because it already knows that THAAD does not pose a threat to its strategic or tactical missile systems.

While deploying THAAD would improve South Korean defenses against a North Korean attack, it would not be able to intercept Chinese ICBMs launched against the United States. Chinese ICBM trajectories would exceed THAAD interceptor range, altitude, and speed capabilities, and THAAD interceptors based in South Korea would offer the wrong interception profile: They are designed to attack missiles heading toward the interceptors in the terminal inbound phase, not an outbound ICBM flying away in its boost and mid-range phases. Moreover, THAAD’s X-Band radar, which can only see in a 90 to 120 degree arc, would be directed at North Korea, not China. Chinese ICBM trajectories would therefore be outside the X-band radar range, and would not be seen or tracked.

THAAD is also poorly positioned against Chinese medium-range missiles if Beijing decided to attack South Korea or Japan. THAAD missiles would not be able to intercept Chinese DF-21 medium-range missiles launched from eastern China eastward toward South Korea or Japan. Interceptors have to be deployed in front of the radar, making the interception of a “flank-shot” missile not traveling directly toward the radar and interceptors extremely difficult, if not impossible. The THAAD X-Band radar would have minimal, if any, capabilities to monitor Chinese missiles attacking South Korea or Japan.

Deploying THAAD to South Korea is clearly not a threat to China. Beijing’s true objective is preventing improvement in allied defensive capabilities and multilateral cooperation. Once again, China has shown itself to be more critical of South Korean reactions than to the precipitating North Korean threats, attacks, and violations of UN resolutions. On the issue of THAAD, China has taken Pyongyang’s side over Seoul’s, disregarding South Korea’s legitimate security concerns and fundamental sovereign right to defend itself against an unambiguous danger.

In response to Seoul's decision to deploy the THAAD system, China engaged in economic warfare, , including imposing boycotts on South Korean products and closing South Korean stores in China. At the same time, Beijing has refused to fully implement required UN financial sanctions against North Korea for its repeated violations of UN resolutions.

China wants to exercise a veto over Seoul’s defense procurement and national security decisions. While it may be Seoul’s largest trading partner, Beijing clearly does not have South Korea’s best security interests at heart.

Deploying THAAD on the Korean Peninsula would enhance South Korea’s defense against potentially catastrophic nuclear, biological, and chemical attacks. The deployment would impede Pyongyang’s ability to engage in coercive diplomacy and would augment deterrence by reducing the chance of success of a potential North Korean missile strike. The THAAD missile defense system in South Korea would work both to improve protection against the North Korean missile threat and to lengthen the fuse of war by reducing the need for a preemptive attack against the North.

The decision to deploy THAAD is a sovereign right that Seoul should base on the national security objectives and defensive needs of the nation. South Korea had demurred from redressing this national security shortfall out of concern of agitating Beijing. However, Seoul should not subordinate the defense of its citizens to Beijing’s economic blackmail.

Seoul and Washington should make clear to Beijing that they will not succumb to pressure tactics when it comes to defending national security. Instead, China should focus its ire on North Korea, which has continually defied UN resolutions by developing nuclear weapons and missiles, causing South Korea and the United States to take necessary defensive actions.

Bruce Klingner is senior research fellow for Northeast Asia at the Heritage Foundation. He previously served 20 years with the Central Intelligence Agency and Defense Intelligence Agency, including as CIA’s deputy division chief for Korea.