One of the most legendary successes of the Royal Air Force in World War II was a bombing raid that was written off for decades as a largely symbolic victory, but was actually a technically challenging operation that choked Nazi industry in 1943 and helped ensure that German factories couldn't produce the materiel necessary to win.
A Lancaster bomber with the special Upkeep bomb bay and bomb used in Operation Chastise in May, 1943.
(Royal Air Force)
The Dam Busters Raid, officially known as Operation Chastise, was the result of a series of bombing raids that hit target after target in the Ruhr region of Germany, but failed to significantly slow German industrial output. Planners needed a way to cripple German industry, and large-scale bombing wasn't getting the job done.
So, they presented an alternative: Instead of attacking individual factories and areas, they'd wipe out an entire productive region with the destruction of key infrastructure. Some of the best and most obvious targets were the dams in the Ruhr region.
The dams fulfilled a few key roles. They channeled water to where it was needed, provided hydroelectric power, and kept thousands of acres of farmland protected for regular cultivation.
Workers construct tanks in factories in Germany during World War II. Factories like this one, and the factories that fed them raw materials, were targeted during Operation Chastise, the "Dam Busters Raid."
Destroying the dam would wreak worse havoc, allowing flood waters to damage dozens of factories essential for everything from coke production to tank assembly as well as additional farmland. The raid would tip the scales of 1943 and 1944 — provided they could figure out how to pull it off.
And figuring it out would prove tough. This was before England's "earthquake" bombs, so the weapons available at the outset of the raid were basically just normal gravity bombs. But hitting a narrow dam with a bomb is challenging, and even a direct hit on the top of the dam would be unlikely to actually cause any sort of breach.
It would take multiple strikes, potentially dozens, in almost the exact same spot to really break a dam from the top.
An inert, practice bouncing bomb skips along the water in this video still from training drops by the Royal Air Force 617 Squadron. The bomb is one of the "Upkeep" munitions, the barrel-form of the weapon aimed at destroying German dams.
(Imperial War Museums)
But if the bomb could strike the dam, that would be much different. A bomb strike against the air-exposed side of the dam could heavily damage it, and a bomb in the right spot on the water side of the dam would cause the whole thing to shatter under the combined pressure of the blast and the water.
So, Britain went shopping for options, and they found a weapon under development by British engineer Barnes Wallis, who wanted to create a better bomb for taking out destroyers.
His thought was fairly simple: A bomb with the right shape and spin could skip across the water until it struck a ship. Then, the spin would drive the bomb underwater as it basically rolled itself down the outside of the ship. It would explode under the waterline with a payload much larger than a torpedo, dooming the ship. These became known as the "Bouncing Bombs."
One of the flight crews from the Dam Busters Raid pose in July 1943. Their successful attack made the brand new 617 Squadron world-famous overnight and crippled German infrastructure.
(Royal Air Force)
His weapon was adapted slightly for Operation Chastise. The original "High Ball" design, basically a sphere, evolved into the "Upkeep" bomb, a more barrel-shaped weapon.
The British created an all-new squadron to conduct the mission, the 617. Pilots from across the Western Allies, including U.S., British Canadian, Australian, and Kiwi personnel, were assigned. The plan was for a low-level, nighttime raid targeting three dams in the valley. The squadron began intense training with the special bombs.
The most successful method they found was flying 60 feet above the water at 232 mph ground speed. While this gave the greatest chances of success and minimized the likelihood that surprised, tired anti-aircraft crews would get a shot at them, it also made for spectacularly dangerous and tricky flying.
The dam at Edertalsperre in Germany after the Dam Buster raid. The hole in the dam was estimated to be 230 feet wide and 72 feet high.
At 9:28 p.m. on May 16, 1943, the 133 men took off in 19 bombers aimed at three separate and challenging targets. They flew in three waves and successfully breached two of the dams while damaging the third.
The next morning, the attacks were reported in Germany and England. Germany tried to downplay the results, and Britain played up the success. For a generation, the exact results were in controversy. Even British historians would claim that the attack was over-hyped.
But, newer research has revealed that the raid really was a stunning success, one that was quickly known in the region as the "Mohne Catastrophe." Germany lost 400,000 tonnes worth of coal production in the month of May and had to divert thousands of forced laborers from the coast of Normandy and other sites to repair the damages.
The English King George VI inspects the airmen of the 617 Squadron, the Dambusters, on May 27, 1943, after their widly successful mission.
(Royal Air Force)
The workers had to repair the physical dam before the fall rains or risk the region running low on water and electricity — even after the dam was repaired. They had to repair 100 damaged factories, not counting the 12 factories completely destroyed. Thousands of acres of farmland, necessary to feed the armies on the march, were ruined.
And, all of this came while the German army was desperately trying to stave off Soviet advances and just a year before the Normandy landings, increasing the chances of success there.
In other words, the mission was a stunning success. But it didn't come without cost. Two bombers were lost on their way to the target. One struck the water's surface and another hit electrical wires. Eight bombers were shot down.
53 Allied personnel were killed and another three captured.