The ships served as a unit in I Division, I Battle Squadron alongside the "Nassau"-class ships in II Division of the squadron. They saw combat during World War I, including the Battle of Jutland in the North Sea and the Battle of the Gulf of Riga in the Baltic. All four survived the war, but were not taken as part of the German fleet that was interned at Scapa Flow. When the German ships at Scapa Flow were scuttled, the four "Helgoland"s were ceded as war reparations to the victorious Allied powers in the sunken ships' stead. "Ostfriesland" was taken by the US Navy and expended as a target during Billy Mitchell's air power demonstration in July 1921. "Helgoland" and "Oldenburg" were allotted to Britain and Japan respectively, and broken up in 1921. "Thüringen" was delivered to France in 1920, and was used as a target ship for the French navy. The ship was eventually broken up between 1923 and 1933.