What Is THAAD, What Does It Do, and Why Is China Mad About It?

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What Is THAAD, What Does It Do, and Why Is China Mad About It?

Hint: It’s not about the THAAD interceptor missiles themselves.

What Is THAAD, What Does It Do, and Why Is China Mad About It?
Credit: U.S. Missile Defense Agency via Flickr

Over the past months–and particularly in the days since North Korea’s latest nuclear and satellite tests–there has been a lot of ink spilled on South Korea’s interest in deploying what is known the Terminal High Altitude Area Defense (THAAD) system. A lot of mainstream coverage of the issue, which has China and South Korea at loggerheads, correctly notes that China is worried about the system, but doesn’t quite get at what exactly THAAD is, what it does, and why its deployment on the Korean peninsula is so threatening to China. China’s anxiety over THAAD has gotten to the point where its ambassador to South Korea would suggest that its implementation would destroy their bilateral relationship in “an instant.”

THAAD is a relative recent addition to the United States’ anti-ballistic missile/interceptor toolkit. It entered production in 2008 and is primarily tasked with taking out threatening ballistic missiles in what’s known as their “terminal” phase (the ‘T’ in the acronym). This is actually the first part where a clarification is due. As Jeffrey Lewis recently highlighted in a Foreign Policy column, THAAD, and systems like it, including the Patriot Advanced Capability (PAC-3) interceptor, are designed to hit things as they zoom downward toward the earth–not as they go up.

This may seem like a trivial point, but Japan made a show of deploying its PAC-3 interceptors in Tokyo ahead of North Korea’s latest satellite launch. Of course, the Kwangmyongsong satellite had a one-way ticket out of the atmosphere and wouldn’t be coming back, making PAC-3, or hypothetically THAAD, useless. (North Korea does have a bunch of short- and medium-range SCUDs that THAAD would be great against, though.)

THAAD is particularly well-suited to intercept and destroy short, medium, and intermediate-range ballistic missiles in their terminal phase. Rod Lyon, in a recent post at the National Interest, helpfully catalogues some of THAAD’s tried-and-tested abilities, which attest to that fact. THAAD’s overall operation is similar to many other missile interceptor and surface-to-air missile systems: an X-Band active electronically scanned array (AESA) radar (AN/TPY-2) kicks off THAAD’s interception, detecting the target projectile. THAAD’s fire control and support equipment identifies, verifies, and initiates the launcher. The launcher–a road-mobile erector launcher, to be precise–finally releases the infrared seeker head-equipped THAAD missile which, according to the system’s manufacturer, then uses “kinetic energy to destroy [the] incoming missile.” In plain English, missile meets missile in mid-air; both missiles go “Boom.”

There’s a lot more to THAAD’s feature set. The “high altitude” part of the acronym isn’t there for show: THAAD is able to intercept incoming missiles at endo- and exo-atmospheric altitudes, with a maximum engagement altitude of roughly 93 miles above the earth’s surface. The missile itself can travel at speeds over Mach 8, placing it in the “hypersonic” category. Indeed, THAAD manufacturer Lockheed Martin is interested in developing an extended range THAAD variant to counter hypersonic glide vehicles, including China’s own WU-14.

Keeping this feature set in mind, why is China so upset about a potential THAAD deployment? The answer, I think, has to do more with the monitoring capabilities that are part of the THAAD package. Beijing isn’t, for instance, worried that a THAAD deployment in South Korea would threaten any ballistic missiles it would plausibly fire at the United States–again, THAAD only works against ballistic missiles in the terminal phase and not against inter-continental ones anyway. Lyon evaluates China’s concerns:

China’s right to believe that THAAD surveillance data could be transferred to other BMD assets protecting [the continental United States (CONUS)]. Indeed, one of THAAD’s missions would be to strengthen U.S. defenses against the possibility of North Korean ballistic missile attack on CONUS. So it has to be able to transfer data to CONUS-based radars and interceptors. But the United States already has a THAAD battery deployed on Guam, two AN/TPY-2 radars deployed in Japan (at Shariki and Kyogamisaki), space-based assets, plus a range of ship-borne radars and larger land-based radars in other parts of the Pacific theatre. Would a THAAD deployment in South Korea change much? The short answer is that it could improve early tracking of some Chinese missiles, depending on their launch point. Still, that might not make actual interception of those missiles much easier. ICBM warheads move fast. And sophisticated penetration-aids help to confuse missile defenses.

So, from the Chinese perspective, a THAAD deployment could shift the strategic stability needle ever so slightly away from its status quo equilibrium and advantage the United States, giving Washington better early warning and tracking of Chinese ICBMs. That, in itself, doesn’t seem like a serious impingement on China’s security or its nuclear deterrent. What’s interesting is reading China’s worries about a THAAD and AN/TPY-2 deployment on the Korean peninsula together with murmurs that Beijing is growing increasingly interested in a launch-on-warning nuclear posture. Does a THAAD deployment affect the credibility of China’s second-strike capabilities by giving the United States a greater early warning edge? Perhaps, but, as Lyon notes above, the difference would be marginal given the AN/TPY-2s already in Japan.

Assessing China’s position on THAAD in light of the system’s real capabilities, we should concede that Beijing does have some legitimate reasons to be upset, but I question if the negative implications for China’s security really outweigh the diplomatic cost to the bilateral relationship with South Korea, which had seen a sharp uptick over the past year. Moreover, it’s clear that South Korea’s security would benefit in important ways from a THAAD deployment–Pyongyang’s Toksa, SCUDs, and No Dong missiles would be a lot less threatening.

China and South Korea should be able to come to an understanding, but this won’t be possible as long as Beijing holds to its maximalist position on THAAD, refusing to abide a deployment of the interceptor on the peninsula. Are there alternatives? If you ask South Korea and the United States, then the answer is yes: China could change its approach to North Korea, making this THAAD business less necessary in the short-term. I wouldn’t count on that happening anytime soon, despite news of the United States and China making some progress on harsher sanctions.