Cassandra had a short career, being commissioned in June 1917 and sunk by a mine during the British intervention in the Russian Civil War on 5 December 1918.

She was built by Vickers Limited, Barrow in Furness and laid down in March 1916, launched on 25 November 1916 and commissioned into the Navy in June 1917.

[2] The main armament of the Caledon-class ships consisted of five BL 6-inch (152 mm) Mk XII guns that were mounted on the centreline.

[2] Cassandra was fitted with a flying-off deck and hangar for a fighter aircraft to counter German Zeppelins after August 1917.

Despite these countermeasures, the two German light cruisers Bremse and Brummer managed to evade the patrols, which were deployed expecting German action further to the south, and attacked the regular convoy between Norway and Britain, sinking nine merchant ships and two destroyers, Mary Rose and Strongbow before returning safely to Germany.

[9] On 5 December 1918 Alexander-Sinclair's force was on passage to Tallinn, threatened by a Bolshevik army, when Cassandra struck a mine, part of an uncharted German minefield, near Saaremaa in the Gulf of Finland.