When I was in Korea in the 80's, we went on alert and were told that NK breached the DMZ. We were issued live ammo and grenades right there on the spot and geared up to move out. My stomach had never been so far up into my throat. If NK did a full breach they could go down, and perhaps past, the Pusan perimeter again. We now have very few troops there, but the ROK soldiers are much better than they were before.
The leaders (Kim's) of NK are nuts, but full of hot air and posturing. Just peacocks for the most part, but you never know when he may snap.
True, I think I read that we only have around 23,000 troops there and many of them are not combat troops. The ROK is much better equipped and trained than they were in 1950 but I doubt they could hold off the NK's million man army for very long. The west would have to do some fast and fancy deployment to stop them from pushing to Pusan again. I'm not sure if China would get in it again or not and that's a huge problem for the west.
That's my point, China is going to have to decide long they are going to prop up NK, it has to be costing them really big bucks, of course a lot of that money is coming from us ......