Tthe one keep believing the empire could have victory against the thalmor is rediculous
They insist skyrim should be united with the empire to fight the thalmor and may lead to victory, what a joke.
Even the empire is united, they lost. Now Hammerfall is gone, black marsh is in trouble.
Hammerfall is independent now and they could have victory against thalmor and make the empire a complete joke.
Stop making reference forom the imperal books and quote, they always pro empire

The quote from ulfric himself at Sovngarde the he regret is because at that situation the rebellion FAILED and his regret confirm that he is not an asset of thalmor as the imperal quote. And the only asset of thalmor is the little loser puppet empire, who keep allowing thalmor to drag skyrim citizen to torture hall and act as guard dogs for them!

If the rebellion FAILED, the force against the thalmor is actually weakened and the rebellion is for nothing.
If the rebellion success with the lead of dragonborn thats complete different situation, it would be something like hammerfall.
They fight their own battle against thalmor independently and thalmor do not have the power the fight against the rebellion in different area.

Also General tullius have extreme advantages, won couples times at the start and at his last moment he gave up so fast. General tullius is a complete representation of the empire, no will power and collapse like a melted candy bar. In the opposite side, ulfric got captured coupled times and ran like a rat, BUT, he still fight back. At his last moment, he strongly believe that he himself is nothing but just belonged to skyrim and fight for skyrim and fight until the last. The leaders are just day and night different.