On 30 October 1918, the Ottoman Empire signed the Armistice of Mudros on board the ship while she was anchored at Lemnos in the northern Aegean Sea.

HMS Agamemnon was ordered in 1904 and was the first warship built by the William Beardmore and Company's Dalmuir Naval Construction Works.

She was powered by two inverted vertical triple expansion four-cylinder steam engines, which developed a total of 16,750 indicated horsepower (12,490 kW) and gave a maximum speed of 18 knots (33 km/h; 21 mph).

That was the second day of the opening bombardment of the Ottoman Turkish forts guarding the entrance to the Dardanelles, and the ship immediately joined the attack.

She came under heavy fire from Fort Hamidieh on 7 March, taking eight hits from large-calibre shells; one of them, allegedly a 14-inch (356 mm) round, blew a large hole in her quarterdeck and wrecked the wardroom and the gunroom.

[4] On 25 April, Agamemnon supported the main landings as part of the 5th Squadron, and after that she patrolled to protect Allied minesweeping and netlaying vessels operating in the Dardanelles.

On 2 December, the ship joined the protected cruiser Endymion and monitor M33 in bombarding the Kavak bridge, destroying several spans of it and interdicting Ottoman communications to the Gallipoli Peninsula.

Under both names, the squadron was dispersed throughout the area to protect Allied-held islands, support the British Army at Salonika, and guard against any attempted breakout from the Dardanelles by the German battlecruiser Goeben and light cruiser Breslau.

On 30 October, the Ottoman Empire signed the Armistice of Mudros on board Agamemnon while she was anchored at Lemnos in the northern Aegean Sea.

[6] Based on the earlier experience in radio-controlled British drone weapons, Agamemnon was modified at Chatham Dockyard for use as a target ship between 6 December 1920 and 8 April 1921.

These trials showed that such strafing could harass a battleship, but could not impair her fighting or steaming capabilities, and helped to determine protection for bridge personnel.

[6] Agamemnon also was used to test the vulnerability of battleships to 6-inch (152-mm), 5.5-inch (140-mm), and 4.7-inch (120-mm) rounds fired at her by ships such as the battlecruisers Renown and Repulse while she maneuvered under radio control.

These tests showed that ships protected as well as Agamemnon, such as the later dreadnoughts, would suffer damage to their upper works if struck by such shells, but would not have their steaming or fighting capability seriously impaired even by numerous smaller-caliber hits.