What’s their mechanized look like? Could they storm in with tanks or military vehicles? It seems like we could mow down a major portion of the attackers, if they just stormed in.
Just about obsolete by today's standards.
The North Koreans have old Soviet designed tanks. There is a corridor of flat ground that runs from the DMZ to Seoul, 70% of the Korean peninsula is mountainous. The Commies would send their armor down this corridor but the US and South Koreans know this so it would be a huge kill box from both ground and air attack although the question is would that be enough to stop the Commies from taking Seoul since its only 30 miles from the DMZ.
They have an ample supply of Soviet-era tracked vehicles including Type 82 tanks and assorted APCs. If they're in a functional state of repair is another question altogether. I'm not sure if we have a solid handle on what works and what doesn't.
But even if it all worked, I'm not sure they would abandon their defensive positions to engage in an offensive campaign. Let's face it, they're all about survival. They probably know that even if they take ground, they don't have the air superiority to keep it.
This has been war-gamed seven ways to Sunday, but my guess is they'd hit a confined piece of Seoul quickly with substantial artillery and rockets as a deterrent show of force. What happens after that, would really be up to the South Koreans. I'm guessing that they would cave after sustaining serious casualties. They have well-trained defensive forces, but I don't believe the South Korean people have the stomach for war anymore.
I really don't think it would escalate and we'd just be back to where we were before, only with 10-50K dead South Koreans to bury. It's just a bad situation with no good alternatives.