I've had 3 of the 4 for a while & just purchased Southern Front for $108 (had it in my hands about 15 years ago for $20 & been kicking myself ever since for not buying it

I have played twice; the first time just the basic set as
U.S. - ended with me in control of Eastern Europe & my opponent was left with only 2
counters Soviet MRDs in Munich with heavy damage

(though at the cost of
nuk level 5 - ooops) The second time I had Northern & Persian (we figured points for Southern & calculated them as a draw there - didn't matter) & I played the
Warsaw Pact - I captured
Finland,
Norway,
Denmark,
Belgium,
Netherlands,
Iraq, northern half of
Iran,
SA, &
Germany + all of
Eastern Turkey. the
U.S. &
U.K. forces were surrounded & cut off in southern Bavaria with neutral Austria/Sweden at their backs. My opponent surrendered but we didn't get to level 5. (rules errata) The rules state that to "De-escalate" you only
get 1/
2 the naps that turn - we agreed on the 2nd game that you should still get
all your naps (for future use - or no-one would De-escalate) but can only
Use a total of 1/
2 the # you receive for that turn, on that turn, but can still pocket the rest for latter use - it allowed us to De-escalate & prevent level 5 - we still reached
level 4!!!