Sniper Elite 5

“Two huge Naval Cannons looking over the French coast from the safety of a mountain. They must be destroyed before the Allies can launch Operation Dragoon to retake the beaches of southern France.”
 
This is story related and cannot be missed. This achievement will unlock after completing Mission 11, ‘Landing Force’, on any difficulty playing solo or two-player co-op.
 
In this mission, you are tasked with infiltrating the island of Le Rocher off the coast of Marseille to destroy two gun emplacements that are overlooking the sea. Then you need to disable the nearby lighthouse as a signal to the fleet to begin their invasion.
 
Although there are two optional objectives, three starting locations, one kill list challenge and 13 collectibles (including workbenches) in this mission, there are no achievements for completing or obtaining them. Note that any of the collectibles obtained in this mission count towards the five collectible achievements in the main list.

Note: Completing the two optional objectives in this mission count towards No Stone Unturned (15G).

Primary Objectives:
 

1. Destroy the Gun Battery
   • Option A - Call in the Scuttle Code (2)
   • Option B - Sabotage the Artillery Shells (2)
   • Option C - Sabotage the Generator
2. Neutralize Radio Communications
   • Option A - Disable the Radio Equipment
   • Option B - Sabotage the Cables (2)
3. Neutralize Lighthouse

Optional Objectives:
 

1. Destroy the Docked U-Boat
   • Option A - Activate the Crane Control Panel / Shoot the Explosive Supplies
   • Option B - Sabotage the Fuel Tank
2. Neutralize Anti-Air Guns (2)

Starting Locations:
 

1. Dead Men Cove
2. Ruined Reef
3. South Ridge

Kill List:
 

• Find and kill Hermann Kraus
  • Complete the kill challenge (kill Kraus with poison [the poison is found on a shelf in a first floor storage room in the building just north of the target; poison the cup on the table on the balcony then ring the bell]) to unlock the Sustained Fire Mods attachment

Thanks to 360GameTV for the video: