Board Thread:Lore Discussion/@comment-97.81.240.58-20130603234626/@comment-13446185-20131120033236

"While the Eighth Legion fought a desperate (and doomed) rearguard action on the walls of the city,"

Only the Eight Legion was destroyed in the sack of Imperial city, because they were sacrificing themselves to let the others escape the Imperial City. (legions have 3000-6000 troops in them)

"Titus II divided his forces into three. One army, with the legions from Hammerfell under General Decianus, was hidden in the Colovian Highlands near Chorrol. 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. The second army, largely of Nord legions under General Jonna, took up position near Cheydinhal. The main army was commanded by the Emperor himself, and would undertake the main assault of the Imperial City from the north" 

The force that took back the Imperial City was massive, each of the armies were made of multiple legions.

-The Great War