The Ruhr valley has long served as a primary base of heavy industry for the German nation. In World War II, for example, the region processed millions of tons of raw materials to make the steel used to conquer its neighbors.

The area teemed with factories running round the clock, along with a canal and rail system providing efficient transport to receiving docks. And all around, farmers plied the thousands of acres of land that kept the soldiers and citizens of the Third Reich from going hungry.

And nearby, watching at different points in the valley, standing like majestic monuments to man’s efficiency, laid the sources that made it all possible.

They provided the electricity to keep the machinery running without end, and the water to quench the thirst of the workers, as well as millions of others who depended upon them to carry out their livelihoods. They were, of course, the cluster of dams that controlled the flow of the many rivers which coursed throughout the valley, and whose presence weighed heavy on the minds of British war planners. Such structures were viewed as strategic targets at the top of the list to be destroyed…if they could.

The British war planners knew they had to destroy these dams, but, with no weapons system accurate enough to do the job, the idea remained in limbo even after the war passed through its second and third years. By this point Germany was being bombed, yet the dams stood defiant simply because no one put forth a plan worthy enough to attack them with any effect.

That is, until a gifted British aircraft designer named Barnes Wallis began studying the issue, and became convinced he could find a way to destroy them.

Sir Barnes Wallis

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Over the next several months, this man, designer of the Vickers Wellington medium bomber used in the early raids against Germany, came up with several unorthodox methods to test his theories. The end result was one of the most unusual, yet brilliant, creations in the history of warfare – a bomb that skipped across water as effortlessly as a stone, yet once contacting its target held on to it until it sunk to a predetermined depth and exploded.

Wallis began his tests in Spring, 1942 by rigging a small wooden catapult and slinging marbles across a laundry pail. He then went to the drawing board and made more calculations, and expanded the tests to a small pond, where he flung larger spheres of varying weights at different angles to see how far they skipped, and tested an array of modifications. One of these involved a technique used by naval ships hundreds of years before called skip shot.

A skip shot involved firing a cannon ball just above the surface of the water so that it skipped into the lower hull of an enemy ship, creating a puncture below the waterline. It was here that Wallis ran into a major problem in that, to replicate skip shots, a plane had to fly dangerously low and fast to the point that releasing a bouncing bomb put the aircraft in as much danger as the target. It was unfeasible, and he knew the idea would be stonewalled unless he could find an answer. He searched his past and remembered that, in the sport of Cricket, the bounce of the ball could be controlled if a backspin were applied. He tried again using the technique and was relieved to see the ball skip across the water once more.

His final adjustment before presenting the proposal to Bomber Command’s Air Chief Marshal, Arthur Harris, involved changing the shape of the bomb to a cylinder to better hold its course. Yet the meeting was anything but decisive. Harris rejected the idea, until Wallis played his last hand, showing test footage of the bomb being dropped. The visual presentation finally impressed Harris of its potential, and the green light was given to form 617 Squadron exclusively to carry the bomb, setting Operation Chastise, codename for the mission, on course for a target date of May, 1943.

Wing Commander Guy Gibson

Led by a true pilot’s pilot, Wing Commander Guy Gibson, 617 Squadron consisted of 30 Avro Lancaster four-engine heavy bombers, specially modified with an appendage to carry the bomb under the fuselage. A Ford V8 engine, carried inside the bomber, provided the power to spin the bomb to over 500 rpm prior to release.

Gibson and his men soon set out practicing against various dams in the British countryside. They roared in at full throttle and at low level, becoming comfortable with handling the big plane at such speeds and altitudes. During the practice runs, though, a vexing problem emerged that stumped the crews: it was difficult to know the altitude and distance to release the bomb to ensure it hit the dam at the right speed. They found their drops often caused dummy bombs to run out of steam because they were released too far out, or that the bombs skipped over the dam’s edge due to being released too close.

They set about coming up with answers as unorthodox as the bomb itself.

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To determine the release point, a V-shaped device with prongs on the end that lined up with twin towers on each dam was devised and later replaced for the actual raid by other devices performing a similar function. This guaranteed that the bombardier would know the sweet spot of the bomb release point.

For the proper altitude, two spotlights were mounted, one in the nose and one in the fuselage, which converged when the ideal altitude of 60 feet was reached.

These new methods were tried in practice and worked wonders, allowing consistent hits and reassuring Wallis, who often attended squadron briefings, that success was possible.

On May 13, with the real bombs delivered to the squadron, Wallis and Gibson briefed flight leaders about the targets for which they were training.

The plan involved flying three formations. The first, with nine aircraft led by Gibson, would attack the Mohne dam, the largest of all the targets, and also the Eder. The second, consisting of five aircraft, would attack the Sorpe. The third formation with the remaining aircraft would hit any of the three large dams if necessary, or focus on the smaller dams named Ennepe, Lister and Diemal.

Avro Lancaster four-engine heavy bomber

Two days later, the bombs, each carrying 6,000 pounds of explosive and looking like oversized oil barrels, were affixed to the Lancasters as the crews went through final preparations. For Guy Gibson, the day was somber as he had to bury his beloved black Labrador retriever, who also served as the squadron mascot. Somehow, he buried his emotions as he and the others climbed into their Lancasters that evening. A spurt of smoke from the planes’ Rolls-Royce engines turning over signified the flight line coming to life for a mission that Wallis hoped would change the course of the war.

Formation 2 took off first at 8:28 P.M., flying a longer northern route than Formation 1, which began take-off at 8:39 P.M. in groups of three, leaving in ten-minute intervals. The reserve formation stayed behind and left 9 minutes after midnight on the 17th.

Flying over the ocean at 100 feet to avoid radar, the planes of Formation 2 ran into trouble just after crossing the Dutch coast, when four of the five bombers were damaged or shot down by flak, leaving one aircraft to press on.

Formation 1 also lost a plane after crossing into Germany, when it hit power cables, causing it to slam into a field. Regardless, the formation, spooked somewhat, pressed on at low level and soon began following the moonlit river toward the target.

The Ford V8 engines began winding up the bombs as Gibson raced in, steadying at 60 feet when the two light beams on his plane converged and the dark outlines of the Mohne grew in the windscreen. A quick flip of a switch and the bomb fell free as tracers and spotlights reached out to him.

The bomb skipped over the anti-swimmer nets stretching the breadth of the dam and slammed into its side. Because of its backspin, it hugged the structure as it descended to 30 feet and detonated, shooting a column of water hundreds of feet high.

The dam held.

Another bomber came in, peppered by fire, as its nose gunner blazed away, trying to suppress the multitudes of flashes ripping the plane apart. A wing caught fire and the plane sped over the dam and veered into a forest, exploding in the trees.

Gibson flew near the dam again, trying to draw fire as more planes sped in. More geysers of water shot skyward from hits, until the last bomb from the last aircraft breached the sides and thousands of tons of water cascaded from the collapsing wall. An artificial river with a tsunami-like like surge began to sweep over the valley.

Mohne Dam

The codeword for success was sent, and Gibson and his men sped away into the night, on the lookout for any sign of night fighters tracking them.

At the Eder damn, British attackers found the target undefended but the terrain problematic for successful runs, with one aircraft making six approaches before releasing. Another aircraft’s bomb exploded on the rim of the dam and severely damaged the plane, before a third plane’s release successfully breached the dam. Water spurted forth and began swallowing up the countryside.

Eder Dam

Sorpe dam came under attack, but because the bomber crews used the length of the dam instead of a frontal approach, they did not spin their bombs. After several unsuccessful runs through anti-aircraft fire, their attacks finally bore fruit when the top-most portion of the structure breached, though it didn’t collapse like the Mohne or Eder.

3rd formation planes arrived later over the Sorpe, but fog proved too dense and secondary dams were targeted, with resulting attacks against the Lister and Ennepe coming up short before the last Lancaster winged off into the night.

Anxious minds, among them Barnes Wallis, waited in the darkness for the approaching planes. The first set down at 3:11 A.M., with continuous arrivals until the last at 6:15 A.M. It was a bunch of weary crews that stepped from their planes as estimates of their casualties began. In all, of the 19 aircraft sent, 8 were missing, along with 56 men.

Upon hearing this news, Wallis was shocked. It took Gibson to console him, saying “We all knew when we took off there was a chance we wouldn’t come back. It was a chance you took on all operations.”

Back in Germany, villages disappeared, bridges were swept away, and all hydroelectric power in the Ruhr was cut as the confluence of water redefined the landscape. The attack surprised the Germans, who began working round the clock even before the tides calmed.

Within a few months they managed to get the dams functional again, but not before seeing their coal production fall by 400,000 tons in May. Thousands of laborers were shifted to repair the damage. Hopes for a war-changing mission were dashed, however, as the German recovery was quicker than expected, and weapons flowed from the Ruhr before summer was over. In all, it sized up to be a minor British victory.

Victory or not, something unusual happened after word of the attacks reached the British public. Papers proclaimed the daring mission, and soon its participants were courted as heroes by a population longing for the first real good news of 1943. The aircrews were invited to Buckingham Palace and personally decorated by King George, only to return and fly more missions right up to the end of the war, while the squadron itself, now called ‘The Dam Busters,’ was destined to live on beyond the conflict to where today it finds itself waiting to transition to the F-35 Joint Strike Fighter.

Quite a legacy.