The United States military has begun deploying the THAAD missile defense system in South Korea this week, a long-awaited move for the South Koreans that face an increasingly significant threat of North Korean missile attack.

The Terminal High Altitude Area Defense (THAAD) system is a defensive weapon platform designed specifically to shoot down short and medium range ballistic missiles.  According to Lockheed Martin, the primary contractor tasked with the project, each system is comprised of five primary components: the launcher, the interceptors, a radar system, a fire control unit, and support equipment.

The system works fairly simply: the advanced truck based radar first identifies a missile launch, and those manning the THAAD assess and identify the threat.  They then launch an “interceptor” at the missile.  The interceptor fires like a traditional missile, but is not equipped with an explosive warhead, instead it impacts the offensive missile and destroys it with kinetic energy.

Each THAAD battery includes at least six interceptor launchers that can carry up to eight of the kinetic energy missiles each.  The lack of explosive warheads on the interceptor missiles speaks to the platform’s distinctly defensive capabilities, but the Chinese have voiced a number of complaints about the presence of the THAAD systems not because of the potential for missile strikes, but rather because of the powerful radar system at the heart of the THAAD defensive strategy.  The Chinese believe the radar systems (AN/TPY-2 X-Band radar) on board each THAAD battery could be used to spy on Chinese airspace – and as a result, have voiced serious objections to its deployment in Japan or South Korea.

“We firmly oppose the deployment of THAAD,” said Geng Shuang, a spokesman for China’s Foreign Ministry on Tuesday. “We will resolutely take necessary measures to defend our security interests.”

“All the consequences from this will be borne by the U.S. and the ROK,” he added, referring to South Korea. “We strongly urge relevant parties to stop deploying it and not travel down the wrong path.”

The need for a THAAD missile defense system in South Korea has never been more palpable, however, as the North Koreans have tested medium range ballistic missiles a number of times in recent months.  Earlier this week, Kim Jong Un himself oversaw the launch of four missiles into the Sea of Japan, three of which landed within 250 miles of the Japanese shore, an area commonly accepted as Japan’s exclusive economic zone.  Some have suggested that these launches were intended to demonstrate (or to practice) North Korea’s ability to target and effectively destroy American military installations on the Japanese island – where more than 50,000 American service personnel are currently stationed.