The United States Navy began it's participation in WWI on April 6, 1917. This happened inmediatly after the declaration of war on the German Empire, after more than two years and a half of president Woodrow Wilson trying to keep the US out of the war.
The main focus of the US Navy was to convoy supplies and men to France and Italy, and to counter-attack enemy U-Boats in the Atlantic and Mediterranean seas. U-Boat stands for 'Unterseeboot' which literally means 'Undersea Boat'.
Very few decisive submarine maneuvers took place because of the US late entry to WWI, and the main ships from the navy never really engaged the German Empire fleet.
