Well, sort of true.
Minor Game of Thrones spoilers from Clash of Kings:
Spoiler When Stannis Baratheon assassinated Renly, Renly's troops all swore fealty to him.
I'm not saying all the Imperials would, but I can see some of them doing it. Not everyone is an idealist. Some men just want food on the table.
Not enough to stand against the Thalmor might, and if the empire tries to take back Skyrim it gives the Thalmor a better chance of winning.
What Thalmor might? Every book on the Great War announces that the thalmor lost tons of men. Add that with slow elven reproduction times and the Elves are actually hurting more than the Empire is.
And if he stays out of the war in order to fight the weakened victor Skyrim will be a threat to Hammerfells rule of Tamriel, as from what I have seen he is too proud to swear fealty to the the stronger country, possibly leading to another war giving the Thalmor a chance of rebuilding.
That could be a future thing, but in the meantime I don't think Hammerfell cares as much about conquering Tamriel as they do killing the Dominion. That's my opinion though.
I'm not sure I understand this.
I'm saying Bethesda wouldn't have made it a choice to join the Stormcloaks if the Stormcloaks weren't a legitimate choice to combat the Thalmor with.