https://www.npr.org/2022/01/08/ [login to see] /us-missile-defense-thaad-south-korea-north-korea-china
A short hike in Seongju county, some 135 miles southeast of Seoul, brings you to the top of a small mountain. To the north, you can see the high-rises of Gumi city. Just in front of you lies a former golf course, with an old clubhouse, some shipping containers on the grass and six mobile missile launchers with their tubes pointing north, toward North Korea.
The launchers are part of the Terminal High Altitude Area Defense or THAAD system that the United States installed in 2017.
The base is a symptom of a growing arms race in Asia. The system is to defend against potential North Korean missiles, which have only in recent years been able to reach any part of the Korean Peninsula.