Not too many pajama wearing kimchi eating SOB's anywhere else than in N.Korea.
They start it and we'll bomb them so hard and so long that there won't be much left.
In order for the NK's to do much damage they'll have to MOVE that dug-in army of theirs...and light off their artillery.
Once these things start moving they become targets...and easy targets at that. China knows it. Russia knows it. Japan knows it. Even the NK generals know it. Our air dominance in any/all theatres ensures no real army can move without our tolerance of same.
Simply put, the best way to strike the NK's is to PROVOKE them into doing something stupid. Then it's slaughter time...
Yes, Seoul would take a BIG hit for a day or two...but it wouldn't be the US fault:)