There is this wonderful old guy who comes into the shop who had the misfortune of working with Korean Special forces in the late 60's. He told me about Blue House and the Battle for the Poplar tree and sent me links about them and other Korean insanity. He comes by and bullshits with me and who ever is around a few times a week. If you studied history by just reading about the things this guy was standing next to when they happened you could stay busy and entertained for years. His body was shattered in Nam, came back and did a thousand jobs, ended up being a ship and port engineer for a few decades. He's interested in everything, reads all the time and has more worldly wisdom than most anybody I've ever met. One of the kindest people I've met in a long time as well. One thing I took from his stories is that Korean special forces guys are a particular and terrifying type of monster.
Not exactly cross-border, but the proximate cause of the Crimean War was a bunch of monks fighting over who gets to put put the star on the tree at Christmas. When you want a war, something's gotta suffice.