We had a game where Axis totally dominated, I mean, allied pieces were basically off the game board, put away, done. We called it day, left the game as it was, one of the players came back over the next day, and it was Germany/Italy VS Japan, where within 5 hours, Japan ruled the world :)
We only did something like that once, but was a cool variant. I don’t think I would like to start that way, but continuing a war after its over by a new declaration or war was a nice touch.