Final answer:
The Sussex Pledge was a promise made by the German government during World War I to limit its use of submarine warfare against civilian vessels.
Step-by-step explanation:
The Sussex Pledge was a promise made by the German government during World War I to limit its use of submarine warfare against civilian vessels. It was made in response to the sinking of the French passenger ship Lusitania in 1915 and the sinking of the French passenger ferry Sussex in 1916. Under the terms of the Sussex Pledge, German submarines would warn ships before attacking and ensure the safety of occupants before sinking the ship.