Maverick Scientist and Daring Airman Flood Hitler’s Industrial Heartland
Germany’s industrial heartland lay in the Ruhr Valley, whose waters were regulated by a series of dams. For years, British contingency planners had explored the feasibility of destroying those dams. Many proposals were examined, but none produced a plan that stood a reasonable chance of success. The problem was accuracy: theoretically, a big enough bomb, such as the 10 ton Earthquake Bomb that burrows deep underground before exploding, could destroy a dam by seismic waves if dropped from 40,000 feet. However, no bomber existed at the time that could carry such a heavy bomb to the required height, then accurately drop it close enough to the dam to destroy it.
Finally, an eccentric British scientist, Barnes Wallis, solved the problem. A smaller bomb, provided it went off against a dam wall at a sufficient depth, would destroy the dam. However, the Ruhr dams were protected by underwater torpedo nets to prevent that. Wallis figured out a solution: bounce a bomb over the water’s surface and over the torpedo nets like a skipping stone, until it struck the dam’s wall. It would then sink down the wall, and once at the requisite depth, explode. The surrounding water would concentrate the blast against the dam, resulting in a breach.
To get the explosive to skip on the surface, then sink along the dam’s wall after striking it instead of bouncing back, Wallis devised a spinning drum filled with explosives. A bomber would approach the dam flying low above its reservoir, and at the proper height and distance from the target, release the explosive drum, which a motor had set to spinning counterclockwise. The bomber’s speed would propel the drum skipping over the water surface, bouncing over the underwater torpedo nets. Once it struck the dam, the drum’s counter-rotation would ensure that it hugged the dam’s wall while sinking. Then, at the proper depth, hydraulic pistols would detonate it.
In March of 1943, a special Royal Air Force unit, 617 Squadron, was formed under the command of a daring 24 year old daring Wing Commander, Guy Gibson. Staffed with experienced pilots and crews, 617 Squadron was to be an elite aerial commando unit. Gibson’s aircrews trained in modified Lancaster heavy bombers, fitted with a motor in the bomb bay to spin the explosive drum, which had to be released 60 feet above the water to properly skip. To determine the correct height, two spotlights were placed on the bomber’s front and rear, and angled so their lights would meet at the water’s surface when the bomber was precisely 60 feet above water.
19 Lancaster bombers took off on the night of May 16th, 1943, flying low on a route carefully chosen to avoid known antiaircraft concentrations. Losses began early on, and two bombers had to turn back after one flew too low and struck water, losing its explosives, while another had its radio damaged by flak. Soon thereafter, a third bomber was shot down, a fourth crashed after striking electric towers, and a fifth went down after flying into power lines.
Guy Gibson made his attack run at the first dam, the Mohne. He then flew across the dam to draw antiaircraft fire while other bombers made their approaches. One bomber was lost and another damaged, but the dam was finally breached after the fifth bombing run. Gibson then led those bombers that that still had explosives to the second dam, the Edersee. It was undefended but, the angle of approach was difficult, and made even more dangerous by fog. After numerous aborted runs, it was finally breached. The attack on a third dam, the Sorpe, failed.
The breached dams caused flooding that killed about 1700 civilians. The greatest impact was the loss of hydroelectric power to factories and residences in the Ruhr for two weeks, as two power stations were destroyed and seven more were damaged. Coal production also dropped, declining 400,000 tons that month. The raid gave a boost to British morale as an impressive feat of derring-do, and Guy Gibson was awarded a Victoria Cross. 617 Squadron, known thereafter as the “Dam Busters”, went on to fly further successful special raids.