The attack finally began on 16 May 1943. The outward flight maintained very low levels throughout. Several planes were lost, including one that crashed into high tension cables at 11.50pm, 2.5 miles (4km) north-east of Rees in the Lower Rhine area of Germany. This was the consequence of the low-level approach, of course, as was the experience of another Lancaster that actually skimmed the surface of the Zuider Zee in the Netherlands, ripping the bomb from its brackets and spraying seawater into the fuselage before the pilot managed to recover. Gibson dropped his bomb first, but the aim was poor and it fell away from the target. A second aircraft was hit by flak and the bomb overshot the target, blowing up beneath the Lancaster that had dropped it. Gibson thereafter flew to draw fire as other Lancasters dropped their bombs, until eventually one struck home and the Möhne dam collapsed with a roar. In contrast, the Eder dam was not well defended: the Germans had assumed it would be impossible to attack as it was situated in a deep valley. Pilots made repeated passes until they were confident that the dam could be mined, and only then dropped their bombs. The Eder dam was eventually breached and — with both dams destroyed — the German factories downstream were severely damaged. The nearby Sorpe dam lay in a winding valley that was unsuitable for the bouncing bombs, and was instead attacked by dropping the bombs as conventional inertial weapons; even though it was hit, it was not significantly damaged by the raids. As a result of the raid, hydroelectric power generation from the dams was interrupted, and a considerable propaganda victory was scored. The supremacy of British secret weapons research was widely celebrated in the UK, though the Nazis also claimed success in minimizing the interruption to power generation, and in the fact that the British could not bring down the Sorpe dam.
Although the raids were seen as an astonishing and heroic success in Britain, there were tragic civilian losses. At least 1,650 people died in the subsequent floods, most of them Allied prisoners and forced labourers held in Nazi prison camps. At least 500 were female Soviet prisoners. This raid was one of the incidents which led to Article 56 of the amendment to the Geneva Convention agreed in 1977, which outlawed attacks on dams ‘if such attack may cause the release of dangerous forces from the works or installations and consequent severe losses among the civilian population’. What was regarded at the time as a heroic act of immense difficulty would now be categorized as a war crime against helpless civilians. Nonetheless, it is difficult to see how the Ruhr could have been disabled otherwise, especially when viewed under the pressures of a world war. When news of the civilian losses became known there was much distress in London and Barnes Wallis was medicated as he was otherwise unable to sleep. The Allies did not follow up the raids; conventional high-level bombing would have deterred the Germans from restoring the dams to use, but no plans for this were ever brought into play. Although Barnes Wallis wrote that Germany had been dealt a blow from which it would take years to recover, by 27 June that same year full water output had been restored, and the hydroelectric plant was back to generating power. The greatest damage was actually to the domestic residences and prison camps, and also to German agriculture. Farms and livestock were washed away and took years to recover.
And the long-term repercussions? There were smaller versions of bouncing bombs planned by the British, for use against shipping. The Highball bomb was fitted to a cradle underneath a Mosquito B-IV, though it never came into service. Although bouncing bombs did not become a feature of post-war military strategy, the legend of the Dambusters raid was perpetuated in books and films. The 1955 black and white British movie The Dam Busters became, and remains, one of the most successful films about the war.[3]
There was an immediate response to the bomb by the Germans. After the Lancaster crashed from hitting high-tension power lines, the intact mine was removed from the wrecked plane by the local troops, who initially thought that it was a reinforced auxiliary fuel tank. Once its true nature was realized it took just ten days for the German engineers to draw up detailed blueprints of all the design features and they set out to build a bouncing bomb of their own. The first constructed was code named Kurt and was a 850lb (385kg) bomb built at the Luftwaffe Experimental Centre in Travemünde. The initial trial was from a Focke-Wulf Fw-190 but the importance of backspin was not recognized by the designers, and the bomb leaped high in the air after release, posing a danger to the aircraft. The German engineers later produced a similar bomb fitted with a rocket booster, which could strike the surface of water at speed and skip for some distance; but it was not a success and in 1944 development work was finally stopped.
The fact that the Germans found an intact bomb was due to a vital factor overlooked by the British designers. As we have seen, these were essentially mines fitted with depth charges. The bomb that overshot — because it was never immersed in water — was never going to explode, and so it was recovered intact. A conventional time fuse should have been fitted, and then the weapon would have functioned as conventional bomb if it overshot the dam. And the Germans missed something equally crucial — the fact that the bombs were spinning. It was the backspin that gave the bouncing bombs their awesome ability to ricochet so far across the water. This remained a military secret long after the war; indeed, you will note that there is no mention of spin even in the movie of the Dambusters. Although Barnes Wallis advised on the film, and it is painstakingly accurate in many respects, he was prohibited from releasing this vital piece of information and the public never knew.
The drawings and diagrams were ultimately all lost, and little technical detail remained. In 2011 Ian Duncan, a director with the British documentary company Windfall Films, recreated a scaled-down version of the bouncing bomb, with Dr Hugh Hunt of Cambridge University in charge of the experiments. They began logically (as did Barnes Wallis) with small spheres leading onto increasingly large projectiles, ending up with a half-size bouncing bomb with which they successfully targeted a purpose-built dam. The physics proved interesting: just as Barnes Wallis had calculated, the lower the bomb was dropped, the further it travelled.
The Americans had tried to make use of this principle immediately after World War II. Because they were sent every British military secret, their designers were aware of the need for backspin, and they also knew that a low launch altitude helped maximize the trajectory of the spinning mine. They copied the British design of the Highball weapon, renaming it Baseball. Initial investigations were promising, so — to maximize the distance the bomb would travel — they decided to launch it at 25ft (7.6m), less than half the altitude of the British Dambusters. This was such a success that the officials reckoned the pilot should fly even lower and see how far the bomb went this time. As the plane sped above the water at the perilously low level of 10ft (3m) the bomb was dropped and bounced perfectly — so much so that it smashed up through the fuselage, completely severing the aircraft’s tail. The plane flew on momentarily and then smashed into countless fragments as it hit the water at speed. The surviving film of the incident makes the whole event so obviously predictable, and one can only sympathize with the compliant pilot who either thought it would be good idea at the time or was simply following orders.
3
The film itself had spin-offs, for extracts were even included in the Pink Floyd movie
‘Dam Wars’: the images from
‘Star Wars a la The Dam Busters’: this less expertly runs