Back on thread - cognisant that I wouldn't have a clue what I am talking about:
Three immediate dangers.
The artillery - not of which all can reach Seoul as Stratfor pointed out - just the rocket assisted shells and the big Stalin organ type rocket launchers. Have to take those out. How many are there? Thousands? Well dug in? Target them first?
The solid fuel rockets. Mobile TELS - next in the firing line - might not be able to respond as quickly as a gun, but not far behind. Do you know where they are and how do you find them?
Then the infantry and armour. Massed onslaught as they head south. How to deal with them?
I actually wonder if the nuclear threat is a huge red herring.
The conventional threat is so much more immediate and dangerous - having walked through those Seoul shopping mall bomb shelters in 2000 as a journo.
It seems to me that the US and SK would need a massive pre-emptive strike in order to contain the NK conventional threat - huge aerial force projection combined with a massive TLAM launch.
They'd need to take out the Norks within an hour or so to limit shelling of Seoul etc.
NK would see it coming a mile off.
A very difficult problem for any battle planner to solve.
Would be interested in the perspectives of anyone who may have more insight than I do.