Since the beginning of Hitler's re-armament of Germany in contravention of the terms of the Versailles treaty, the British Government had looked at ways to degrade Germany's industrial capacity in the event of war. In February 1943, the Assistant Chief Designer at Vickers Armstrong, Barnes Wallis, revealed his idea for "air attacks on dams" which would deprive the German arms industry of its vital water supply and cause a "disaster of the first magnitude".
Wallis, in co-operation with the Air Ministry had designed and tested a "bouncing bomb"; codenamed 'Upkeep'. In the days before computer-aided precision bombing, Wallis bouncing bomb would maximise the chances of actually hitting a dam and destroying it. His test showed that it would need to be dropped from 60 feet, at an angle of 7 degrees from the horizontal, a ground speed of 220mph and with back spin. It would then bounce across the water to the target and on contact with the dam, crawl down the under-water face and explode.
Impressed with the concept, Air Chief Marshal Sir Charles Portal, Chief of the Air Staff, ordered Barnes Wallis to prepare the bouncing bombs for an attack on the Möhne, Eder and Sorpe dams in the Ruhr for May 1943.