North Korea's nuclear weapons program stems from a reaction to the US deploying cannons and missiles on the border and pointing them at them in 1958.
This freaked them out a little.
Rather than a vanguard invasion force, I've read that the 28,500 US military personnel in Korea today exist as a sort of political tripwire. There aren't enough of them to hold the line, let alone successfully invade the North, but their deaths in the event of a conflict would commit the US to the fight.
I'm bemused that this is considered a controversial fact.
Edit : I meant to say nuclear missiles and artillery were deployed in 1958 which is what NK reacted to, they had conventional weaponry deployed before that.
In this light, I'll note that Bush the elder removed US all nuclear arms from the Korea peninsula in 1991 (although Pyongyang's certainly still in range of American missiles and bombers):
http://thediplomat.com/2013/03/not-a-good-idea-american-nuke...
Overall, my impression is that North Korea fears a conventional ROK/US invasion much more than a nuclear exchange scenario, and that this fear (rather than of American nuclear artillery, missiles, etc) has been the primary motivation behind their nuclear arms development.
I don't think a conventional US invasion is likely, hence my comment. I also don't think the situation would be different if NK didn't have a nuclear arms program, given their alliance (or subordinate relationship?) with China.
True, but:
* given the US's nuclear submarine, bomber and ICBM capability this was likely seen as a moot point. The threat was still there. Indeed, one of the reasons the US cited for removing its nukes was that they were no longer needed.
* They actually never fully confirmed this withdrawal until 1998.
>Overall, my impression is that North Korea fears a conventional ROK/US invasion much more than a nuclear exchange scenario
I think so too - for now, but it probably didn't seem that way in 1958 when they had nukes pointed at them.
>I also don't think the situation would be different if NK didn't have a nuclear arms program
I do. They'd be much more vulnerable to invasion. Given the US's military history in the last half century (Vietnam, Iraq, etc.), I think their fear of that is somewhat justified.
Their alliance with China does provide some protection but relations have soured over the last few decades and if I were them I wouldn't see it as a relationship they could depend upon.
Nukes were pointed at them because they've invaded South Korea first.
A peaceful, East Germany-style transition would be preferable, but I also think it's possible that an invasion to free the current generation of North Koreans could do more good than letting them die under another Kim's boot. Millions live there today in deprivation and fear, not to mention the hundreds of thousands of North Koreans reportedly living (and dying, via torture and brutal execution) in Nazi-style concentration camps. Needless to say, a successful reunification of the Korean peninsula would benefit future generations of North Koreans as well.
If you're curious, here are the books which formed my impression on the subject:
"Without You, There Is No Us," https://www.amazon.com/dp/B00JTC9QBO/ref=dp-kindle-redirect?...
"The Cleanest Race: How North Koreans See Themselves and Why it Matters," https://www.amazon.com/dp/B004EWETZW/ref=dp-kindle-redirect?...
"Dear Leader: My Escape from North Korea," https://www.amazon.com/dp/B00IBYRQ18/ref=dp-kindle-redirect?...
http://www.latimes.com/nation/la-na-trump-allies-20160930-sn...
I suppose if the government in Seoul no longer felt it was worth the cost, they could stop paying and ask the Americans to leave.
EDIT: Oh yeah, why did you put "protection" in quotes? That's exactly what it is. The US doesn't pay North Korea to break the South's windows, if you'll excuse the mixed metaphor.