All eight of the ships were heavily modernized between 1898 and 1904; the reconstruction included lengthening the ships and equipping them with new boilers. All eight ships were mobilized briefly at the start of World War I in August 1914 as the VI Battle Squadron, though by August 1915, they had all been withdrawn from service and employed in secondary roles. All were stricken from the naval register in 1919 after the end of the war and subsequently discarded; three of the ships, Frithjof, Odin, and Ägir were converted into merchant ships and served in this capacity throughout the 1920s. The rest were broken up for scrap by the early 1920s.