On the outbreak of war in August 1914, she was seized by the British authorities whilst in Port Said, Egypt and was requisitioned for service under the Red Ensign in January 1915 to operate seaplanes.

[1] On 17 August, both Anne and Raven II spotted for the French armoured cruiser Jeanne d'Arc as she bombarded Tarsus.

[5] At the end of March, Raven II was sent to the Red Sea to attack Turkish troops threatening Aden; she carried one two-seat Short floatplane and five Sopwith Schneiders for this operation.

After a preliminary reconnaissance mission, on 2–3 April her aircraft dropped ninety-one 20-pound (9.1 kg) bombs as well as leaflets urging the Arab auxiliaries to desert.

The ship returned to the Syrian coast for patrols and was transferred to Kastellorizo in early July to conduct aerial reconnaissance and bombing missions in that area.

[6] The East Indies and Egypt Squadron reassembled in late August with Raven II, Anne and Ben-my-Chree and the aircraft from the three carriers attacked the Turkish supply dump at El Afule for thirty minutes.

Raven II was then sent to the Adalia area on the Turkish coast where her aircraft bombed a factory at Fineka and searched for U-boat bases[7] On 1 September, the ship was in Port Said preparing for another sortie into the Red Sea when she was hit by a bomb dropped by a German aircraft (probably the first successful air attack on an aviation vessel).

Raven II relieved Anne on 26 October in the Red Sea and her aircraft bombed Turkish forces advancing on Rabigh and Yenbo on 10 December.

Engine problems forced a Short 184 to make an emergency landing on 21 April in the Maldives; the crew rejoined the ship on 6 May after a series of adventures that inspired Rudyard Kipling's story "A Flight of Fact".