If North Korea uses a nuclear weapon offensively, I'd say that it's almost certain to be on Seoul. I very much doubt that they have the capability to deliver one even that far from their own border, honestly, but it's a major target that might just be within their technical capabilities to pull of. At which point my prediction would be that China would wash their hands of the entire mess and start talking to the ROK about how to keep things from overheating on the new border once the DPRK was finished. It would, after all, be much cheaper and easier for them than paying for their own invasion, leaving aside the chances that rolling in themselves would wind up with them running into the South Korean Army with the latter in no mood to be reasonable.
What the occupation of the former Democratic People's Republic of Korea would be like... is hard to say, honestly. At the start, it'd probably be pretty ugly, bloodshed wise, yes. How long that would last once the food shipments started arriving is another question, and one that, like many other questions about how decisions get made by anyone in North Korea, no one outside that country has enough data guess at with any confidence, but my own estimate would be 'not long', especially if the power doing the occupying was the ROK.
I think that you overestimate the 'closeness' of the relationship between the PRC and DPRK. My read is that the sole value the former places on the latter is that they're less potentially threatening to have across the Yalu than the ROK would be. The deployment of a nuclear weapon in such an openly destabilizing and aggressive manner would rather change that at the same time that it changed South Korea's evaluation of the potential benefits of occupying the place.
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"V, did you do something foolish?"
"Yes, and it was glorious."
What the occupation of the former Democratic People's Republic of Korea would be like... is hard to say, honestly. At the start, it'd probably be pretty ugly, bloodshed wise, yes. How long that would last once the food shipments started arriving is another question, and one that, like many other questions about how decisions get made by anyone in North Korea, no one outside that country has enough data guess at with any confidence, but my own estimate would be 'not long', especially if the power doing the occupying was the ROK.
I think that you overestimate the 'closeness' of the relationship between the PRC and DPRK. My read is that the sole value the former places on the latter is that they're less potentially threatening to have across the Yalu than the ROK would be. The deployment of a nuclear weapon in such an openly destabilizing and aggressive manner would rather change that at the same time that it changed South Korea's evaluation of the potential benefits of occupying the place.
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===============================================
"V, did you do something foolish?"
"Yes, and it was glorious."