During WWII he joined RAF Bomber Command's Operational Research section, where he was the expert in charge of the use of a precision navigation system called G-H. Field-based, he advised on operational techniques to use the equipment most effectively. Notably, he helped No. 218 Squadron RAF in Operation Glimmer, a diversionary "attack" on D-Day that distracted and pinned-down German defences while the real attack occurring 200 miles to the east. His G-H-equipped bombers flew low, in tight circles, dropping window over radar transponder-equipped small ships, in order to deceive the German radars that they were the main invasion fleet.