Re:
That's why the US Army pulled back from the border. The whole border region is meant to be a killing zone ~50km in depth.
Once North Korea starts moving any assets (and it will need to) into & across the DMZ, its going to be fair game for the AF and army aviation.
No one bothers to plan for a North Korea invasion. Its absolutely meaningless. Despite all public US announcements about bringing democracy to xyx. Its a waste of time and effort. May have been worth something in 1950 but today,50,000 sq miles of North Korean rock and sand is not even worth one human life.
Containment has been extremely effective in the case of North Korea.
If however, hypothetically, the US does intend to invade North Korea, AAA isn't going to be a deterrance. There's just too much cluster/precision munitions capabilities to exploit.
First, the USAF will shift the F15/A10 units from coast to bases in SK, Jpn. The CVGs will plot their courses.
F-15s & F-18s will establish high level air superiority capabilities with a few F16s/18s focussing on mid-altitude wild weasel missions to take out the abysmal SA-2 & 5s radar sites.
JSTARs/Global hawks will start flying at altitudes far beyond AAA ranges to identify AAA sites along the routes (with satellite intel as well).
They will assess the least defended route along the breath of Kaesong to Kumgangsan and then blast a narrow route all the way to Pyongyang with everything from A10s to B2s. Won't even need choppers except to ride shotgun.
NK Assets outside of the route that move towards the route will be interdicted in designated killzones. That takes away a significant proportion of AAA capabilities because of the dispersal.
After OIF, I don't think that's a capability beyond the USAF and ROKAF. Kim has a legitimate fear of US might (although a misjudge reading of US intentions).