Here is the full list of all 19 IWO: Bloodbath in the Bonins achievements.
Complete a game without transferring any reserve units
Land on both beaches
Research Iwo Jima
Transfer all reserves in one game
Learn the game's rules
View the Credits Screen
Reach the conclusion of an invasion
Attain a US defeat
Capture 2 Sectors (excluding Mount Suribachi)
Defeat 110 Japanese Defenders
Defeat 70 Japanese Defenders
Capture Mount Suribachi
Defeat 40 Japanese Defenders
Defeat 20 Japanese Defenders
Start a new game
Attain a draw
Attain a US victory
Attain 2 US victories
Attain 3 US victories