I agree N. Korea would not be easy to beat if even possible, they have been gearing up for war with the us for years now. They wont leave N. Korea to attack but have amazing defenses against pretty much anything the us can send their way.
All important bases are under granite and all communications are fibre optic.
Have a read of this
http://www.rense.com/general37/nkorr.htm
Written a few years ago so things will have changed both ways