This seems bugged. As the Union, the ai captured Norfolk. I counter attack and they are led by Farragut as a 3 star general using his navy ratings as a ground commander and they had 450+ cannons because their entire fleet was sitting there. Needless to say, I got pretty much creamed. Known issue?
I could see a few cannons from a parked fleet being used, but not all of them, and Frarragut is a naval commander, not a ground tactics guy.