A gung-ho strategy that works (I admit, it also caught me off guard...) is, to use the eastern approach, avoiding any congestion and entangling of your divisions, it's possible to reach and capture Pusan in 3-4 turns. This however worked (when I got defeated by a human opponent) ONLY when most of the units are orange/static for whatever reason. I couldn't move/react at all. It's worth a try. Use the amry support level motorcycle, tank, AA, specvial forces and rush down with 2-3 divisions. I would like to try it out against a human, so... up for a test run, version 3.4.201?
P.S. My opponent who achieved that feat (with a tad of luck, ofc) was zukov