Korean history is really deep in M. Night Shyamalan level plot twists going back thousands of years. And every step of the way the people who live there have been fucked over in one way or another.
Most recently Japan occupied them... Quite brutally, once Japan was defeated in WW2 a pro China guy up north and pro US government in the south formed...
That fuckwad Dean Acheson, US Secretary of State at the time hinting that the US wasn't interested in Korea, leaving communist China and Russia to encourage Kim to try to take the whole thing. Acheson is more to blame than Stalin imo.