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The Bouncing Bombs of Barnes Wallis

Barnes Wallis’ battle to build the Ruhr dam bombs

When World War II started, Barnes Neville Wallis was assistant chief designer of aircraft at Vickers-Armstrong and respected for his innovative geodesic airframe designs for the Wellesley and Wellington bombers. Ironically, the weapons designer was also a pacifist. Appalled by the large numbers of casualties being caused by the belligerents, Wallis set his engineering mind to work on seeing what he could do to shorten the war, and thus reduce the loss of life, a process he called “An Engineer’s Way to Win the War.”

Bouncing bomb demonstration

Movie still, showing an inert, practice version of the Upkeep bouncing bomb being dropped during a training flight by members of RAF 617 Squadron at Reculver bombing range, Kent. The bomb’s designer, Barnes Wallis, and others watch the practice bomb strike the shoreline. Imperial War Museum photo

His solution was to attack Germany’s war industry, concentrated in the Ruhr River Valley, at its power source: the dams on the Ruhr River and its tributaries. The destruction of even a few would have an enormous domino effect. His idea was not original. In the late 1930s, the British Air Ministry had made a similar study. But, the largest bomb in production was a general-purpose 1,000-pound bomb, much too small to have an impact on a dam, and bombing accuracy was notoriously poor. As the Ruhr dams would also be protected by concentrations of anti-aircraft artillery, the Air Ministry concluded such attacks would be too costly and impractical.

Wallis submitted a proposal to create specialized bombs, the largest being behemoths he called earthquake bombs. Those were rejected because they were too big for existing bombers. But two smaller skip-bomb designs capable of bouncing over protecting torpedo nets, codenamed “Upkeep” (for dams) and “Highball” (for warships), received sufficient endorsement for Wallis to conduct experiments.

“You know, Mr. Wallis, we don’t think these dams are very interesting as targets.”

– Professor Frederick Lindemann, scientific adviser to the British government

Numerous trials were conducted against a disused dam at Nant-y-Gro in Wales, at Chesil Beach and Reculver along the Channel coast, and at Loch Stripen in Scotland. Their success caused the admiralty to place an order for Highball skip bombs. But Upkeep’s success created a controversy in the Air Ministry. Bomber Command’s Air Chief Marshal Sir Arthur “Bomber” Harris denounced Upkeep, calling it “Tripe of the wildest description.” He also refused to release a squadron of Lancasters, the only bomber large enough to carry Upkeep, for use as dam busters. Even within Vickers, Wallis came under attack, with one colleague saying, “Stop playing the fool and go and do something useful for the war.” Harris’s boss, Chief of the Air Staff Air Marshal Sir Charles Portal, however, was impressed by the trials and ordered Harris to release three Lancasters for Upkeep testing.

Dr. Barnes Wallis

Dr. Barnes Wallis holds a model of a deep-penetration bomb. Imperial War Museum photo

But Wallis’s relief over even this small victory was short-lived. Other members of the Air Ministry who hated Upkeep decided to deep-six it by applying pressure on Vickers Chairman Sir Charles Craven. The next day Wallis found himself in London being dressed down by Craven for being “a damn nuisance.” Craven concluded his tirade by saying, “You are forbidden to work any longer on this absurd bouncing bomb project.” The stunned Wallis replied, “Well, sir, if I’m not serving the best interests of the company and the country, I had better offer you my resignation.”

But too many people in influential places found promise in Upkeep. Knowing of his fondness for inventive weaponry, they managed to apprise Prime Minister Winston Churchill of the project, who ordered copies of the Upkeep reports. As suspected, the reports fired his imagination and Churchill ordered it be given top priority. Wallis was back in business.

By now it was the end of February. Because the raid had to be launched when the Ruhr dams’ reservoirs were at their peak, that meant the attack had to happen in May – eight weeks away! Construction of bombs, modifying a squadron of Lancaster bombers to carry them, and selection and training pilots and crews went overnight from being nonexistent to moving at high speed.

On the night of May 16, 1943, Wing Commander Guy Gibson led Squadron “X” (later 617 Squadron) on an attack of selected Ruhr dams. Hours later the Möhne and Eder dams were breached, and the Sorpe Dam damaged. A fourth dam, the Bever, was attacked but not damaged. The cost was heavy, with eight bombers shot down and 53 crewmen killed. But photos from a bomb damage assessment reconnaissance mission revealed the mission to be a success.

Möhne Dam Aerial Reconnaissance Photo

An aerial reconnaissance photograph showing the breach in the Möhne caused by No 617 Squadron, Royal Air Force’s raid on May 16, 1943. The Eder Dam was breached in the same operation by means of ‘bouncing’ bombs designed by Dr. Barnes Wallis. This spectacular feat of precision bombing had tremendous propaganda value, although its practical effects were less great than some had hoped. Imperial War Museum photo

Reich minister Albert Speer wrote in his book Inside the Third Reich, “That night, employing just a few bombers, the British came close to a success which would have been greater than anything they had achieved hitherto with a commitment of thousands of bombers.”

A delighted Harris told Wallis, “Now you could sell me a pink elephant.” Wallis responded with two “earthquake” bombs: Tallboy, a 21-foot monster weighing almost 12,000 pounds that was used on V-weapon launch sites, concrete U-boat pens, and against the battleship Tirpitz and heavy cruiser Lützow, and the even larger (22,000-pound) Grand Slam, also used against V-weapon launch sites and bridges.

BBC conducted an interview of  Wallis, and the archive can be listened to at: A video of Operation Chastise that mixes newsreel footage with that from the movie can be seen on YouTube at: In addition, YouTube features a German television news story about an amateur film taken of the wrecked Eder Dam and the aftermath of the flooding:


DWIGHT JON ZIMMERMAN is a bestselling and award-winning author, radio host, and president of the...