Here is the full list of all 7 Civil War: Gettysburg achievements.
Destroy 3 enemy units in a row without losing any of your own.
Destroy 8 enemy units in a row without losing any of your own.
Destroy 12 enemy units in a row without losing any of your own.
Complete 1 scenarios on Hard difficulty.
Complete 5 scenarios on Hard difficulty.
Complete 10 scenarios on Hard difficulty.
Complete the tutorial.