[2][3] The Acheron-class (redesignated the I-class in October 1913) was an improved version of the Acorn-class destroyer which had been built for the Royal Navy under the 1909–1910 shipbuilding programme.

On 16 August 1914, within days of the outbreak of war, the First Destroyer Flotilla engaged an enemy cruiser off the mouth of the Elbe, which is reported with great verve by an author writing under the pseudonym "Clinker Knocker" in 1938: On Aug 16th we had our first brush with the enemy, and our flotilla received a sample of German gunnery which our own gunners acknowledged was excellent.

At daybreak we chased a German collier and made contact with a powerful armoured cruiser, which opened fire on us with 8.2 inch guns.

Fearless led us in a determined attack to close with torpedoes, but the large German Cruiser foiled our intentions by running for home, and we did not blame her.

Phoenix was escorting the Australian troopship Ballarat when she was attacked by a German submarine on Anzac Day (25 April) 1917 in the English Channel.

[3][14] HMAS Warrego made an unsuccessful attempt to tow her to Valona (now Vlorë in Albania),[15] but she sank within sight of the port at 13:10 in position 40°23.5′N 19°14′E / 40.3917°N 19.233°E / 40.3917; 19.233.