I don't think you understand the tactical situation in Korea. Last time I checked, Pyungyang had more than 50,000 artillery pieces pointed at Seoul. Nukes or no nukes, any invasion/incursion/liberation/exercise(insert favorite term here) would be met with massive retaliation, death and destruction for our favorite S. Korean city. It is the country equivalent of a hostage stand-off with a "gun to our head." In situations such as this there literally is no force, except sanctions and internal collapse that can work because S. Korea will have to be willing to sacrifice its largest city in the process. The only comfort I get is that the USGS says it has monitored no "unusual" seismic activity on the Korean Penninsula -- N. Korea is famous for its fiction and we can pin some of our hopes on the idea that they don't really have the technology ... not just yet.