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