When the British began to prepare for war in July 1914, the ship was refitting at Malta. Her refit was cut short and she joined the rest of her squadron in the southern approaches to the Adriatic. She was involved in the pursuit of the German battlecruiser "Goeben" and light cruiser "Breslau" at the outbreak of World War I, but was ordered not to engage them. On 10 August "Duke of Edinburgh" and her sister ship were ordered to the Red Sea to protect troop convoys arriving from India. While on that duty the ship captured the German merchantman "Altair" of 3,200 tons GRT on 15 August. While escorting a troop convoy from India to France in November 1914, "Duke of Edinburgh" provided cover to three battalions of infantry that seized the Turkish fort at Cheikh Saïd at the entrance to the Red Sea. The ship then landed a demolition party, which blew the fort up on 10 November; she then rejoined the convoy.