With thousands of artillery pieces in the mountains north of Seoul, it would be a bloodbath. Our best tools for dealing with them are all in mothballs (I remember well Dad telling me about the New Jersey turning hill 368 into hill 320), and there are some things which require large amount of explosive delivered in a penetrating package at a high arc. Precision is alot, but it ain't everything.

Conventional war on the Korean Peninsula would be damned ugly. There would be two humanitarian crises, the first being the massive amount of civilian casualties in Seoul and the surrounding areas, the second being integration with the North and South after the war was over.

China holds Kim's leash, so it's not going to happen. We get into a war with Korea, China backs the North, and the US simply voids all China's bond holdings as a result of their support of the north.

Russia, at that point, would be sitting on the sidelines laughing, as China is their enemy in more ways than one.