If missiles and launchers are being moved that would still mean the system in Korea is combat effective; it would just have a smaller inventory. However, if its radar or C2 systems are being moved then it would be combat ineffective:

The United States has been moving parts of its Terminal High Altitude Area Defense (THAAD) anti-missile system from South Korea to the Middle East, the Washington Post reported, citing two officials.
The reported movement of parts of a THAAD missile defense system comes amid media reports that the U.S. military stationed in South Korea has shipped out some of its military assets amid an intensifying war in the Middle East.
“The Pentagon is moving parts of a Terminal High Altitude Area Defense (THAAD) system from South Korea to the Middle East,” the report said.
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