I spent good portions of the last 7 years in Korea working the area for the Army. I know who is there. What we have is token opposition to the force in being that we are opposing. We're purposely set up many miles beyond the DMZ to avoid an incident short of actual war. That said, 2ID, the primary US ground force in Korea, has something like 15,000 effectives. It's even worse than it sounds when you say 29,500 - most of the rest are logistics related personnel. Lots of tail, limited teeth. The effectives are the people primarily at risk in the event of NK aggression, other than the Air Force pilots, who are very limited in number. The logistics tail will retreat as quick as they can to Daegu and then Busan, in the event of a NK breakthrough.