I honestly don't think a real "organized" war of that kind is likely to ever happen again. We have long since passed the point where the major actors are just too big and powerful to risk war with eachother, so they engage in little more than proxy wars against eachother's minor interests.
Even that doesn't really seem to describe the present day since the major powers major interests are so aligned they don't even proxy war with eachother so much as with the fallout from the decades worth of mess they made with their proxy wars.
Man are you out of touch with what's happening in the world. It's exactly that type of thinking which predominated prior to WW I and is considered a major contributing factor to it starting. Putin's rhetoric and brinkmanship likely has the risk of a major war closer now than it was during the cold war.