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The problem with taking an offensive approach here is that Seoul, population 10.5 million (2.3 million more than New York City, is 31 miles from North Korea (roughly the distance from New Orleans to Slidell). I don't doubt for a single minute that North Korea would relish going out in a blaze of glory and taking Seoul with it. I think you have to either wait it out or wait until he forces your hand, because the outcome will be truly terrible if it escalates.
Tokyo isn't that far away either as the crow flies and they hate Japan as much as they do South Korea. . NK isn't serious until they start massing troops on their southern border. If that happens,look out.