Here is the full list of all 21 1976 - there are Back to midway achievements.
Operation Blue Beard
Bombing of Quatterdam
Operation Cherry
Operation Candlelight
Bombing of Bartovia
Maginot line
Battle of El Bansoori
Doo-Wop Raid
Mendel Bombardment
New Caledonia Campaign
Frampton Blitz
Battle of Burroughsland
Operation Ausgang
Operation Lontano
Terranova Campaign
Battle of Midway
Workshop level 1
Workshop level 2
Workshop level 3
Workshop level 5