Didn't take long for someone to go "winner: none" and that's somewhat understandable given the obvious damage nukes do; however it can be won (or rather "won") if the power last standing in an exchange doesn't fall after the others do, at least for a while, a sort of a funny way of saying, the one-eye man is king in a scenario where an eye is taken for an eye (or rather nuked). Thing is, there are a lot of complex factors into nuclear weapon usage and effects, of which are so vast, that even the launching part is hard to determine (outside of accidental launches like the Petrov incident), especially as many nuclear warplans are still classified. Though at least humanity might recover from a war, only to inherit a broken wasteland that would rival the crappiness of third world countries; that's what fallout shelters are for.