Time is key for this process to work.

Once you've selected a mission with the right conditions (Close to your current port + Mission intelligence: Battleship was recently seen in this area), move out as fast as you can to maximize your chances of finding and intercepting the Battleship.

There currently are 3 Battleships in the game:

• Nelson
  
• Rodney
  
• Royal Oak (she does not count for the achievement)

Notes:

• The selected mission does not necessarily have to be a Patrol Mission. However, selecting a Patrol Mission helps, since the Battleship will spawn in the designated patrol area.
  
  
• The AM3-AN1 Patrol Missions seem to have consistent Battleship spawn patterns (vicinity of Scapa Flow).

1. Be ready to move out of port before starting this process.
   
   
2. Find a mission as close to your current port as possible. You will most likely need to refresh mission sets to find the right conditions.
   
   
3. Required Mission intelligence for the selected mission: Battleship was recently seen in this area.
   
   Important Note: The AM3-AN1 Patrol Missions seem to have consistent Battleship spawn patterns (vicinity of Scapa Flow).
   
   
4. Select the mission, then instantly create a Manual Save. You will then be able to reload that save as many times as you want, to hunt the Battleship over and over again if needed.
   
   
5. Get to the patrol area as fast as you can.
   
   Time is key: The Battleship moves fast (12 knots or 22 kilometres per hour).
   
   The Battleship is part of a Warship Task Force. The Battleship is not part of a convoy.
   
   
6. Spam the hydrophone inside the patrol area.
   
   If you don't detect the Warship Task Force, move to a new location inside the patrol area then use the hydrophone again.
   
   
7. While using the hydrophone, look for a specific communication from your radiomen: Ship propellers, warships, small group, bearing <n> degrees.
   
   This communication means your radiomen just spotted a Warship Task Force.
   
   When Mission Intelligence = Battleship was recently seen in this area, the Warship Task Force inside the patrol area has a Battleship.
   
   
8. Move in to intercept the Battleship.
   
   
9. Get rid of the Destroyers and Corvettes protecting the Battleship.
   
   
10. Sink the Battleship.