Combined Operations Headquarters was a department of the British War Office set up during World War II to harass the Germans on the European continent by means of raids carried out by use of combined naval and army forces. Admiral of the Fleet Roger Keyes was the first director, from 17 July 1940 to 27 October 1941, replaced first by Lord Louis Mountbatten and then Major General Robert Laycock (October 1943 – 1947). The main forces used by Combined Operations were the Commandos.