"Euryalus" was assigned to the reserve Third Fleet when she returned home in 1909.At the outbreak of the war in August 1914, she was assigned to the 7th Cruiser Squadron, tasked with patrolling the Broad Fourteens of the North Sea in support of a force of destroyers and submarines based at Harwich, which protected the eastern end of the English Channel from German warships attempting to attack the supply route between England and France.