I'm still impressed with what Paradox "attempted" to do with this game, and PARTS of it work amazingly well, but there are other aspects which don't work well (poorly, or not at all), and even stranger ones which sometimes work, and sometimes don't.
SOMETIMES, my supply system is inextricably linked to those of my allies (leaving the faction leader with a surplus of "free" supplies while the other faction members starve in their own capitals), other games they remain independent.
Some games, the war with France goes "normally"; other times, Paris ends up surrounded by over 100 brigades of troops, but the German AI refuses to take the city, even after 2 years. If some other country triggers "Vichy" instead, or if some other country takes the SU or GE, there really needs to be some check to see who is occupying the capital. If it's the EXPECTED attacker, run the "special event", if not, use the NORMAL surrender mechanisms instead. It makes no sense when the UK takes over GE, for example, and the US is somehow given all of Germany, especially if the US is not at war, or even in the Axis.
Strategic bombing with ONE air unit can reduce a medium sized country's industry and supply stockpiles to all but 0, leaving JUST enough to fly a single bomber group to do the same to the opponent. Meanwhile, AAA evaporates in a couple of days, in spite of the slight "easing" of this in the 1.4 patch (AAA took almost NO damage from strategic bombing, historically, since it was located AROUND the target, not IN). I had one game where the SCW turned into a permanent stalemate (not a single province changed hands in over 2 years), due to just such a case of mutual annihilation.
There should be NO reason why GE or UK (or IT and FR) should have any interest in competing with the SU for Sinkaing province (Japan might, but for some reason, they generally seem to be more interested in influencing Belgium or Finland instead). Most games, there's a multi-year tug-of-war over the place, between all three factions. Politically, there should be no reason why the US would "run for protection" to the Allies when Japan's antics in China start to increase its Threat on the US. There is even LESS reason why Australia should run to the Axis in the same situation.
In over 10 "starts", I have yet to see a game reach a point where an East-West confrontation occurs between GE and SU. In EVERY case, something has gone irrecoverably wrong with the game, leading to either a total "walkover" or a complete breakdown in playability. FR totally abandoning the Maginot Line, GE leaving a single division to garrison the entire Russian Front, launching and "stoking" unsupportable foreign or amphibious invasions (or squashing ONE partisan in a remote province with 30+ divisions) until there's nothing left to defend the home front, and other blatantly unbelievable things have occurred in EVERY game so far, with every patch.
About all I can do to enjoy "parts" of the game is to pick an isolated corner of the world and just "go for it" until the AI does something to completely break the game. Otherwise, the only way I can make it play either historically or even "rationally" is to play Germany and use every diplomatic trick in the book, plus an occasional reload and "fix" of another country, to keep it "on a believable track", whether "historical" or not. Even that hasn't gotten the game past around '41 without something else degenerating into absurdity or a total game crash.