WORLD HISTORY

Detailed explanation-1: -Britain’s blockade across the North Sea and the English Channel cut the flow of war supplies, food, and fuel to Germany during World War I. Germany retaliated by using its submarines to destroy neutral ships that were supplying the Allies.

Detailed explanation-2: -Germany then retaliated by creating its own blockade around the British Isles and English Channel and began using a policy of unrestricted submarine warfare, destroying all Allied and neutral party ships.

Detailed explanation-3: -Unrestricted submarine warfare was first introduced in World War I in early 1915, when Germany declared the area around the British Isles a war zone, in which all merchant ships, including those from neutral countries, would be attacked by the German navy.