After their commissioning into the German fleet, all four ships served in the II Division of I Battle Squadron. Two of the ships, "Nassau" and "Posen", took part in the inconclusive Battle of the Gulf of Riga in 1915, during which they engaged the Russian pre-dreadnought "Slava". The four "Nassau"-class ships took part in the Battle of Jutland on 31 May and 1 June 1916; they suffered only a handful of secondary battery hits and limited casualties. In early 1918 "Rheinland" and "Westfalen" were sent to Finland to support the White Finns in their civil war, but "Rheinland" ran aground off the Åland Islands in April and was severely damaged. At the end of World War I, the four ships were seized as war prizes by the victorious Allied powers and sold for scrapping.