THAAD and China's Nuclear Second-Strike Capability

Hours after North Korea’s early March launch of a four-missile salvo into the Sea of Japan, the United States delivered and began deployment of part of the Terminal High Altitude Area Defense (THAAD) system. “Continued provocative actions by North Korea, to include yesterday’s launch of multiple missiles, only confirm the prudence of our alliance decision last year to deploy THAAD to South Korea,” said the head of U.S. Pacific Command, Admiral Harry Harris, the next day, underlining the rationale behind the decision.

China, South Korea’s neighbor and the United States’ great power competitor in Asia, has long been vocally opposed to the deployment of THAAD on the Korean Peninsula. In response to the deployment, Geng Shuang, a Chinese foreign ministry spokesperson, noted that China was “resolutely against the deployment of THAAD by the U.S. and the ROK in the ROK, and will take firm and necessary steps to safeguard our security interests.”

For starters, let’s put to rest the misconception that China’s opposition to the THAAD deployment is because it is worried about the interceptor shooting down its missiles. As the ‘T’ indicates in THAAD, the system is only capable of intercepting projectiles in their “terminal” phase (or as they’re hurtling toward the earth in descent). Unless China would consider firing ballistic missiles at South Korea, THAAD will do no good against its missiles (say, its intercontinental ballistic missiles going toward the United States in a nuclear exchange).

For China, opposition to THAAD is simple: it’s all about the X-band AN/TPY-2 radar unit that accompanies the interceptor battery and aids in targeting. The radar unit has yet to be delivered; it is expected to arrive in South Korea in April.

To be clear, China hasn’t been coy about specifically pointing to the radar issue. In fact, it has been explicit. Chinese Foreign Minister Wang Yi has made multiple references to the “X-band radar” that accompanies the THAAD battery, pointing out last February that it “goes far beyond the defense need of the Korean Peninsula.” This isn’t a case of Beijing nebulously stating its opposing to the deployment in terms of its national interest.

However, by that same token, China has turned down good faith offers from the United States for technical talks and consultations on the THAAD deployment in South Korea. The Obama administration, looking to assure China that the deployment wasn’t all a ruse to hurt China’s interests, invited Beijing to talks as early as a year ago. “We will be very glad and hope we’ll have the opportunity to sit down and talk with China about those very technical limitations and facts about the system,” Rose Gottemoeller, the former undersecretary of state for arms control and international security, had said at the time. China rebuffed those offers. Chinese Foreign Ministry spokeswoman Hua Chunying noted last year that THAAD was “certainly not a simple technology issue” for China.

So, what is it about THAAD — specifically about the X-band AN/TPY-2 radar accompanying the battery in South Korea — that so vexes China? What is it about this radar that drove Beijing to initiate a thorough dismantling of a slowly-but-surely improving bilateral relationship with South Korea through 2016 and early 2017?

Two Competing Hypotheses

There are two possible serious explanations for how THAAD infringes on Chinese national interests. One is less convincing than the other. I’ll address both in order, beginning with the less convincing explanation.

The first hypothesis is that China may fear that the AN/TPY-2 radar at the former Lotte Group golf course in Gyeongsangbuk-do will give the United States unprecedented surveillance insight into sensitive Chinese missile testing and development work deep within the mainland.

This may sound convincing at first glance, but there’s a few reasons why it doesn’t hold water. First, the South Korean THAAD deployment is not the first AN/TPY-2 deployment from the United States; nor is it even the first deployment of an advanced radar by the United States to the region. The U.S. already has two AN/TPY-2 installations in Japan, at the Kyogamisaki Communications Site in Kyoto prefecture and Shariki in Aomori prefecture.

Second, while we have no watertight estimates on just how capable the AN/TPY-2 radar is and in what configurations, even the most generous estimates don’t leave the Gyeongsangbuk-do unit capable of any useful surveillance deep into the Gobi desert, where China has its most active and sensitive missile testing ranges. (AN/TPY-2 range estimates go from “several hundred miles” to 3,000 km.) I’ve mapped out the ranges below with the most generous range estimate of 3,000 km, using a Chinese ballistic missile impact range that Thomas Shugart at War on the Rocks recently revealed as a test-bed for potential People’s Liberation Army Rocket Force preemptive warfare tactics (i.e., a site of surveillance interest for the United States).