It wasn't, either, His [weakened] force was part of Mede's strategy to retake the IC. Mede's decision to recall Decianus' Legion was a sound one, as it was clear the Thalmor's focus had switched to Cyrodiil, and the Empire's ability to sustain a 2-front war wasn't very feasible.

Yes, and because of Decianus's actions, they didnt know about his army in Cyrodiil, contributing to the attack, as they were caught off guard.

"The Aldmeri were unaware that he was no longer in Hammerfell, possibly because the Imperial veterans Decianus had left behind led Lady Arannelya to believe that she still faced an Imperial army."

While I am not as fanatical as you, I agree o the love of that book. A Legates report that does more to support the Stormcloaks than the Empire as a source? What is not to love?

Agreed. Started reading your book again btw. Slowly, but I'm going.