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Dambusters: The Truth Behind the Legend

The Mohne Dam in North Rhine-Westphalia after the Dambusters raid

16 May 2018 marks the 75th anniversary of a military raid like no other. Partly thanks to the stirringly patriotic film starring Sir Michael Redgrave, the “dambusters” occupy a special place in the British imagination. Amid the ugly atrocities of World War Two – amid the vicious battles, indiscriminate massacres and genocidal outrages – the dambusters operation stands apart in our minds as a kind of swashbuckling adventure, a heroic example of great British pluck, with inanimate objects rather than human beings as the target of the attacks.

But the truth is, Operation Chastise was a frighteningly dangerous mission. It required technology and pilot skills that had never been seen before. It overcame cynicism at the top levels of the British military, and would cost the lives of many RAF pilots, as well as many, many more civilians. Yet the goal was seen as worth it. The Ruhr Valley, with its power plants and dams, had long been regarded as a prime target by the British, and dealing it a crippling blow was calculated to cause significant damage to the Nazi war machine.

The problem was that the dams in the Ruhr were too resilient to be attacked by conventional bombs from the air. They were most vulnerable at their base, but torpedoes wouldn’t work because the dams were shielded by vast underwater torpedo nets that would stop the projectiles in their tracks. This is where a lateral-thinking engineer steps into the picture.

Barnes Wallis had already made his mark in the history of aviation, having helped design airships like the R100. Now, he applied his analytical skills to the vexing issue of the Ruhr dams. Somehow, explosives had to hit the dams in exactly the right spot, while overcoming the anti-torpedo defences. He hit upon the solution in his back garden, filling a bathtub with water and sending a set of marbles skimming across its surface. These marbles were the prototype of what would become world-famous as the “bouncing bombs” of the dambusters raids.

While many people may picture the bombs – codenamed “Upkeep” – as spherical, they were actually cylindrical. And they were real monsters to carry, with Lancaster bombers having to be specially adapted to accommodate their formidable cargo. Each bomb was fixed into position using large calipers, with a tough belt pressing against the heavy casing. This belt, attached to a motor, was there to apply backspin to the bomb just before release. To ensure it would bounce correctly, it would have to be spinning at precisely 500 rpm, and then dropped at exactly 60 feet over the water while the plane was flying at 232 mph. Only then would the bomb be able to bounce nimbly across the water, avoid the torpedo nets, and then sink at the right spot to detonate at the base of the dam.

To ensure it would bounce correctly, it would have to be spinning at precisely 500 rpm, and then dropped at exactly 60 feet over the water.

It was certainly a bold, even outrageous plan. Too bold for more conservative members of the military, including the RAF’s infamous “Bomber” Harris, who dismissed Wallis’ plan as “tripe” and “the maddest proposition” he’d ever heard. Luckily, the operation was put in the hands of an experienced daredevil of a pilot, the now-legendary Guy Gibson. Despite only being in his mid-20s, Wing Commander Gibson – who’d idolised WW1 flying aces as a boy – had already proven himself as a superb pilot, and was well placed to lead the dambusters on their unprecedented mission.

Following trial runs in England, the pilots departed on the raids in three waves, in May 1943. There were 19 bombers involved in Operation Chastise, with the Mohne, Edersee and Sorpe dams their targets. There were problems almost immediately – one plane flew too low and actually skimmed the sea, which wrenched its bomb off and meant the crew had to return to base. Pilots were killed while making their daring runs on the dams themselves, while still more perished on the way back from the mission.

All in all, 53 of the 133 men we remember as the dambusters died during the mission. Two of the target dams were destroyed, which caused devastating flooding as millions of tons of water burst through the region. Estimates vary on how many died in the man-made tsunami, but it may have been as high as 1,600 people, including hundreds of civilians and POWs. Testimonies by survivors paint a frightening picture – one local boy later recalled how the sound of the water “sounded like win, a great wind”, and another survivor spoke of how “our house was flooded but remained standing while everything else, trees, roads, gardens, was swept away”. Humans and farm animals alike were drowned together.

To this day, controversy surrounds the dambusters raid – some argue it wasn’t a strategic success, and did little lasting damage to the German war effort. Others counter that it was an invaluable boost for Allied morale during the darkest years of the war. Either way, the place of the dambusters as one of the most audacious and breathtaking military assaults in British history is assured.