South Korea’s New Missile Defense Tech Isn’t a Cure-All For North Korea

South Korea's US-supplied THAAD is now operational, but it's no magic bullet.
Policemen walk along residents and peace activists marching toward a Lotte golf course in Seongju where the U.S. and...
Policemen walk along residents and peace activists marching toward a Lotte golf course in Seongju where the U.S. and South Korea are stationing a Terminal High Altitude Area Defense (THAAD) battery to counter missile threats from North Korea.Aflo Co. Ltd./Alamy

A year after it was first announced, the United States-provided missile defense system meant to guard South Korea is fully operational. The device has sparked controversy and pushback from China, but it's a powerful symbolic step that should provide some legitimate protection from an increasingly volatile North Korea. It also has some important limitations.

Terminal High Altitude Area Defense systems like the one now functioning in South Korea have a strong track record of missile interception in US tests. A THAAD has a range of a little under 125 miles, and can target missiles both inside and just outside the atmosphere. Strategists think of THAADs as an important layer in broader missile defense plans, since they address the in-between area that other specialized systems don't. The systems are mounted on armored trucks to be highly portable, and consist of a digital control system, radar, and reloadable launchers that fire interceptors.

But a single THAAD is far from a magic bullet, and the one now operating in South Korea still leaves that country, many US assets in the area, and US allies like Japan vulnerable to North Korean attack. That's partly because THAADs target medium and intermediate-range ballistic missiles on their descents, meaning they're ineffective against missiles midway through their trajectory. Mostly, though, one simply isn't enough.

"The problem is that given the range of the interceptors with THAAD, you really need at least two and probably three or four THAAD batteries in South Korea in order to defend the whole country," says Bruce Bennett, a senior defense analyst at the RAND Corporation.

Not only that, but the US and South Korea agreed to place that single THAAD in Seongju, about 135 miles southeast of Seoul. That puts it out of range to defend South Korea's capital city, the most likely target if a North Korean attack did occur because of its population and proximity to the reclusive nation.

The THAAD's placement, though, still makes strategic sense, especially from the US point of view. Its locations would help it defend some key US strongholds in the region, and would protect US troop deployments coming in through the southern tip of the Korean peninsula if South Korea ever needs reinforcements.

"That’s the area through which US forces would flow to Korea if they were coming to help the South Koreans defend the country. They would come through Busan, not Seoul," Bennett says. "The US also figured that if South Korea really wants to defend Seoul, they can buy a THAAD battery of their own." The US only had one THAAD to offer so it went to a place that prioritized US interests. President Trump indicated that he thought it would be "appropriate" for South Korea to pay for the installed system, but national security adviser H.R. McMaster confirmed this week that the US would bear financial responsibility.

In its current placement, the THAAD can defend a number of US military bases, like Camp Walker in Daegu and Kunsan Air Base in Gunsan, along with ports in Busan and the southern tip of South Korea. All of this serves South Korean defensive interests as well, but experts doubt that South Korea could afford to purchase additional THAADs on its own any time soon.

So yes, the THAAD going operational in South Korea this week means the US could help defend South Korea during a possible conflict. But as tensions with North Korea continue to escalate, that should only reassure up to a point.