Here is the full list of all 54 Forts achievements.
The base game contains 21 achievements, and there are 2 DLC packs containing 33 achievements.
Complete campaign on Hard
Complete all campaign missions
Complete all campaign missions on Hard
Complete part 3 of the campaign (Hard)
All part 2 theatre medals acquired
All part 2 theatre medals acquired (Hard)
Complete part 2 of the campaign (Hard)
All part 1 theatre medals acquired
All part 1 theatre medals acquired (Hard)
Complete part 1 of the campaign (Hard)
Reach the end of the campaign
Complete part 3 of the campaign
Complete part 2 of the campaign
Complete part 1 of the campaign
Play 10 multiplayer games
Tutorials complete
Complete all mission achievements
All part 3 theatre medals acquired
All part 3 theatre medals acquired (Hard)
Play 10 ranked multiplayer battles