Civilian scientists, flying from Defford with aircrews drawn from the Royal Air Force and Royal Navy, tested radar systems which were to revolutionise the operational capability of Allied aircraft. Early successes with Airborne Interception (AI) systems were demonstrated by John "Cats Eyes" Cunningham and other night fighter pilots. While Air to Surface Vessel (ASV) radar enabled the German U-boat menace to be effectively countered in 1943, and thus was critical to the success of the Battle of the Atlantic. By 1944, H2S radar was enabling accurate navigation and target identification to be achieved by Bomber Command crews, taking part in the strategic bombing offensive.