At the beginning of the First World War, "Bulwark" and the 5th BS were based at Portland and assigned to the newly reformed Channel Fleet to defend the English Channel. After covering the safe transportation of the British Expeditionary Force to France in August, the 5th BS remained in Portsmouth until 4 September when they returned to Portland. They stayed there through October aside from exercises. From 5 to 9 November, "Bulwark" hosted the court martial of Rear-Admiral Sir Ernest Charles Thomas Troubridge for his actions during the pursuit of the German battlecruiser and light cruiser in the Mediterranean Sea in August. On 14 November, the 5th BS was transferred to Sheerness because of concern that a German invasion of Great Britain was in the offing.