Here's some basic info on North Korea versus South Korea. Neither the US nor China will support their respective allies in an offensive war. And neither the North or the South can fight off the other Korea and their ally without support from their own ally. So neither side will actually do anything.

 

On top of that, even is a true war was started, neither side would have anything to gain. North Korea doesn't stand a chance against the South so anyone in power there realizes they would lose everything. And if South Korea wins they'd suddenly have to support 24 million extra people which would destroy their economy for the next 10 years minimum.

 

So to summarize; neither side will ever actually do anything because both sides realize the gains will always be nullified by the losses.

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