She was powered by a pair of four-cylinder triple-expansion steam engines, each driving one shaft, which developed a total of 27,000 indicated horsepower (20,000 kW) and gave a maximum speed of 23 knots (43 km/h; 26 mph).

[8] She escorted the ocean liner RMS Medina in 1911–1912 while the latter ship served as the royal yacht for the newly crowned King George V's trip to India to attend the Delhi Durbar.

[9] After the ship returned to Plymouth in early 1912, Defence was transferred to the China Station, where she remained until December when she was ordered to rejoin the 1st Cruiser Squadron in the Mediterranean as flagship.

The order was cancelled on 14 September when it became clear that the German squadron was still in the Eastern Pacific and Defence returned to the Dardanelles.

Defence, however, had only reached Montevideo, Uruguay by 3 November 1914 when she received word that most of Admiral Cradock's squadron had been destroyed two days previously at the Battle of Coronel.

Defence departed Table Bay, Cape Town on 8 December and rejoined the 1st Cruiser Squadron of the Grand Fleet as its flagship upon her arrival.

The squadron formed the starboard flank of the cruiser screen, ahead of the main body of the Grand Fleet.

At 17:47,[Note 3] Defence and HMS Warrior, the leading two ships of the squadron, spotted the German II Scouting Group and opened fire.

[16] At the time, it was believed that Defence had been reduced to fragments by the explosion, but the wreck was discovered in mid-1984 by Clive Cussler and a NUMA survey of the North Sea and English Channel at coordinates 56°58′02″N 05°49′50″E / 56.96722°N 5.83056°E / 56.96722; 5.83056.

[17] It was dived upon in 2001 by a team led by nautical archaeologist Innes McCartney and found to be largely intact, despite the violence of her sinking.