At the beginning of the First World War, "Formidable" and the 5th Battle Squadron were based at Portland and assigned to the Channel Fleet to defend the English Channel. After covering the safe transportation of the British Expeditionary Force to France in August 1914, "Formidable" took part in the transportation of the Portsmouth Marine Battalion to Ostend on 25 August. On 14 November, "Formidable" and the other ships of the 5th Battle Squadron were rebased at Sheerness because of concern that a German invasion of Great Britain was in the offing. The squadron was relieved by "Duncan"-class battleships of the 6th Battle Squadron and transferred to Portland on 30 December.