On massive complex near Seoul, question of handing combined troop command to ally hangs heavy A soldier passes a restaurant on the Camp Humphreys U.S. military base in Pyeongtaek, South Korea, on Oct. 28. (Photo by Ahn Seong-bok) PYEONGTAEK, South Korea -- The "center of gravity" for the defense alliance between South Korea and the U.S. is a massive military base built on acres of former rice paddies.