When the First World War began, Indefatigable was serving with the 2nd Battlecruiser Squadron (BCS) in the Mediterranean, where she unsuccessfully pursued the battlecruiser Goeben and the light cruiser Breslau of the German Imperial Navy as they fled towards the Ottoman Empire. The ship bombarded Ottoman fortifications defending the Dardanelles on 3 November 1914, then, following a refit in Malta, returned to the United Kingdom in February where she rejoined the 2nd BCS.