There are six secondary objectives to complete in order to unlock this achievement.
Bitanti Village (2)
Signal Advantage – Find the radio operator before he calls for help
The Towering Assassin – Kill the sniper
Regilino Viaduct (1)
Hidden in Plane Sight – Find the downed American pilot; Find the crashed observation plane
Lorino Dockyard (1)
Hello to Arms – Raid the German armory
Magazzeno Facility (1)
Naval Gazing – Destroy the German naval guns (5x); Assassinate the officer in charge of defenses
Giovi Fiori Mansion (1)
The Nazi Propaganda Machine – Find route of propaganda truck; Destroy truck