She became flagship of the Southern Force defending the eastern end of the English Channel from any German attack, shortly after the war began.

[1] She was powered by two 4-cylinder triple-expansion steam engines, each driving one shaft, which produced a total of 21,000 indicated horsepower (15,660 kW) and gave a maximum speed of 21 knots (39 km/h; 24 mph).

[7] A dozen quick-firing (QF) 12-pounder 12 cwt guns were fitted for defence against torpedo boats, eight on casemates on the upper deck and four in the superstructure.

The recently launched Euryalus was laying alongside this wharf, and the fire set ablaze the teak wood sheathing of the cruiser.

[11] Towed to Cammell Laird at Birkenhead for repairs, the ship slipped off the blocks supporting her in drydock and was severely damaged.

Reduced to reserve upon her arrival, she was sent to the North America and West Indies Station in 1906, where she served as a boys' training ship attached to the 4th Cruiser Squadron for the next three years.

[13] 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.

[16] As a result of these losses, she, and her sister Bacchante, were transferred to the 12th Cruiser Squadron to escort ships between England and Gibraltar in early October.

By this time the preliminary bombardments of the Turkish defences of the Dardanelles had already occurred, and the sisters were transferred north in March as the Turks east of the Canal proved to be reasonably quiet.

[18] Euryalus became the flagship of Rear Admiral Rosslyn Wemyss in April, after he was put in charge of the main landings at Gallipoli.

On 29 June she bombarded the barracks in the Yemeni town of Hodeida together with the troopship RIM Northbrook of the Royal Indian Marine.

Rear Admiral Ernest Gaunt relieved Wemyss as commander-in-chief on 20 July 1917 and transferred his flag to Northbrook on 29 August.