[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 (16,000 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.

[9] In September 1902 she visited Greek waters for combined maneuvers with other ships of the cruiser and channel divisions, landing at Nauplia and Argostoli,[16] before she escorted the damaged battleship HMS Hood from Malta to Gibraltar in October.

[17] She was reduced to reserve when she returned home in 1912 and was assigned to the 7th Cruiser Squadron shortly after the outbreak of the First World War in August 1914.

[18] The squadron was 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.

[19] On the morning of 22 September, Aboukir and her sisters, Cressy and Hogue, were on patrol without any escorting destroyers as they had been forced to seek shelter from bad weather.

The weather had moderated earlier that morning and Commodore Reginald Tyrwhitt, commander of the Harwich Force, was en route to reinforce the cruisers with eight destroyers.

[20] SM U-9, commanded by Kapitänleutnant Otto Weddigen, had been ordered to attack British transports at Ostend, but had been forced to dive and take shelter from the storm.

The sudden weight loss of the two torpedoes caused U-9 to broach the surface and Hogue's gunners opened fire without effect before the submarine could submerge again.