Never played Gettysburg.
Just created custom battle, rome vs. greece. Gave myself 100s of urban guards (the elite of the Roman army) gave them the best armour, highest experience etc. and took on 600 greeks with a little cavalry and some repeating ballisters (rubbish) I lost 80 men and killed 600, it was a blood bath! The urban guards were awesome!
On the otherside, I lost my empire yesterday so will need the enthusiasm to start that mission again,