So as can be seen the view across all of Tamriel is pretty bleak. Morrowind is in pieces, Skyrim is engaged in a bloody civil war, Cyrodiil has been beaten and bruised, Hammerfell has been abandoned, Black Marsh is controlled by extreme xenophobes and the Aldmeri Dominion has carved its way from Alinor to Southern Tamriel. A war is brewing, and it's going to be a big one.
How is a next Great War going to go down? We'll assume that the Civil War is currently on hold (Season Unending) so that means the Empire has one-and-a-half provinces, temporary peace with Eastern Skyrim meaning an alliance and the Thalmor are still gripping Cyrodiil's nuts. Hammerfell is still under immense pressure and the Dominion is growing stronger.
How can the Dominion be defeated? How would the Empire and the other provinces go about doing this?