"Derfflinger" was completed shortly after the outbreak of World War I in 1914; after entering service, she joined the other German battlecruisers in I Scouting Group of the High Seas Fleet, where she served for the duration of the conflict. As part of this force, she took part in numerous operations in the North Sea, including the Raid on Scarborough, Hartlepool and Whitby in December 1914, the Battle of Dogger Bank in January 1915, and the Bombardment of Yarmouth and Lowestoft in April 1916. These operations culminated in the Battle of Jutland on 31 May – 1 June 1916, where "Derfflinger" helped to sink the British battlecruisers and . "Derfflinger" was seriously damaged in the action and was out of service for repairs for several months afterward.