During the First World War Keyes was heavily involved in the organisation of the Dardanelles Campaign. Keyes took charge in an operation when six trawlers and a cruiser attempted to clear the Kephez minefield. The operation was a failure, as the Turkish mobile artillery pieces bombarded Keyes' minesweeping squadron. He went on to be Director of Plans at the Admiralty and then took command of the Dover Patrol: he altered tactics and the Dover Patrol sank five U-Boats in the first month after implementation of Keyes' plan compared with just two in the previous two years. He also planned and led the famous raids on the German submarine pens in the Belgian ports of Zeebrugge and Ostend.