As the Germans developed their own technologies, Cockburn expanded his team, first at Swanage and later at
Malvern, with a view to hiding British bombers from German radar. One of the principal weapons for this purpose was Window, known to the Americans as
Chaff, small bundles of metal strips which could cause a radar echo similar to that of a bomber aircraft. Window was such an important innovation that many opposed its use by
RAF Bomber Command, because of the potential consequences if the Germans used similar techniques against British radar. Bomber Command was finally allowed to use Window for the first time on 24–25 July 1943, in the big raid on
Hamburg, leading to a significant reduction in RAF casualties. In the lead up to the
Normandy landings of 6 June 1944, Cockburn worked with
Leonard Cheshire and others on
Operations Taxable and Glimmer. These operations were designed to create an elaborate system of electronic signals that, while using only two squadrons of bombers dropping bundles of Window, would suggest that invasion fleets were heading towards Fecamp and Calais, well to the east of the actual landings. == Postwar ==