The Dam Busters flooding Germany’s Ruhr Area: Operation Chastise (1943)

In 1943 the RAF Bomber Command, led by Air Marshal Arthur Harris, brought together pilots and aircrew to form 617 Squadron. This squadron was tasked with a single, crucial and daring attack, which had the potential to become a very spectacular success. Their task was to attack the heart of the German war industry, using a new, untested weapon: the so-called ‘bouncing bomb.’ With 19 Lancaster bombers, the squadron was sent on its way to put a considerable dent in the German industrial Ruhr area and its surrounding infrastructure.

The Dam Busters

By early 1943, Bomber Command’s strategic night offensive against Germany was stepping up a gear. One factor was the increase in production of four-engined Lancaster bombers equipped with increasingly sophisticated radio-navigation aids. Still, most of Bomber Command’s effort went into the ‘area bombing’ of Germany’s industrial cities rather than attacks on pinpoint targets.

However, there was a set of precise targets which Bomber Command had identified as vital to the German war effort. These were the water reservoirs supplying the Ruhr area, Germany’s main industrial region, with much of its water and electricity. Two dams were especially vital: those of the rivers Eder and Möhne. The surrounding German war industry relied on these dams and the hydroelectricity they generated. Bombing the industry itself had proven unsuccessful time and time again. Yet regular bombings of the dams didn’t damage them enough for it to make a significant impact.  

Wing Commander Guy Gibson (2nd from left) and King George VI (3rd) discussing the Dambuster Raid in May 1943

Initially, Air Marshal Harris didn’t have too much fate in the Lancaster bombers’ ability to destroy the German dams. The special squadron, designated 617, was formed in mid-March 1943 to carry out the attacks. This squadron was commanded by the 24-year-old Wing Commander Guy Gibson. Although relatively young, Gibson had already been prolifically decorated. He was one of the Bomber Command’s most experienced pilots, a meticulous planner and natural leader of men. In total the Squadron consisted of 133 men. And as mentioned it was quite the pioneering mission, because they were to use a new, untested weapon: the ‘bouncing bomb’, designed by Barnes Wallis. 

Wallis was one of Britain’s greatest aero-engineers. He designed the R100 airship and the Wellington bomber, both with geodetic airframes. He developed the bouncing bomb, initially to destroy the Ruhr dams. These bombs skipped over the water like a pebble can be made to skim over a pond. He tested the concept by catapulting marbles over water in a tin bath, firing projectiles across a lake and shooting small spheres along an indoor tank at his laboratory.


Basically, the bomb – codenamed ‘Upkeep’ – was a massive depth charge armed with 3000 kg of Torpex. It was designed to hit the retaining wall of a dam and then sink nearly 10 metres below the surface before it exploded. In late 1942 a Wellington bomber, fitted with special rotating and release gear, carried out a series of tests with the prototype on the south coast near Weymouth. Five months later the RAF finally issued it. They modified it again because its initial wooden casing cracked when it made contact with the water. 

The 133 men of the 617 Squadron gathered at RAF Scampton in Lincolnshire. They were a bit of a mixed bunch, ranging from veterans like the Australian low-flying expert Mickey Martin to relatively new pilots that flew just a few operations. Aside from British pilots, there were 29 Canadians, 12 Australians, two New Zealanders and one American, the Flight Lieutenant Joe McCarthy. All of them had been hand-picked by Gibson for the secret operation. When they arrived at the airbase, they realised their Lancaster’s bomb bays were heavily modified, the first big giveaway that they weren’t recruited for an ordinary mission.

The bomb mounted under Gibson’s Lancaster B III

The subsequent training of the Squadron involved a punishing routine of low-level flying and bombing exercises. There was a lot of focus on precision bombing. Wallis had informed Gibson that the attack would occur at no more than 45 metres above water – which later during the training was lowered to just 20 metres, with the bombs having to be precisely released 389 metres away from their target. Two angled spotlights were fitted to the Lancaster’s nose and rear fuselage to judge the height over water. The beams were designed so that they coincided with the surface of the reservoir when the aircraft flew at the right altitude. The pilot had a V-shaped wooden device, with two nails at the ends of its arms to coincide with the towers and the end of the dam, to judge when to release the bombs. It all seemed a little primitive, but it might have just been crazy enough to work.

Meanwhile, Wallis and his team were still working hard to perfect the design of the bomb. In May the Squadron used full-sized practice bombs to attack canvas towers, and then suddenly things progressed very rapidly. The last exercise happened on May 14th, and the next day Gibson received orders that the mission, Operation Chastise, would commence the next afternoon, May 16th.

The Mission

Bomber Command picked its targets: six dams. Gibson was to lead the main contingent, consisting of three formations of three aircraft to attack both the Eder and Möhne dams. If the mission went well and there were bombs leftover, these would be dropped at the Sorpe. The second wave consisted of five aircraft, attacking the Sorpe. And the third wave, another five aircraft, flew as a reserve, taking off two hours after the first wave, to be directed against any of the main targets or three other dams: the Lister, Diemel and Ennepe. To evade German air defences, the Lancasters had to fly below 150 metres throughout the entire mission.

At 8:30 pm on May 16th, the first contingent took off from Scampton, led by Gibson. They flew into the Ruhr at tree-top height. Before they dropped their first bomb, the pilots already encountered their initial difficulties. The Lancaster flown by Flight Lieutenant Bill Astell flew into a high voltage cable and crashed into a field. Gibson’s Lancaster was the first to attack the Möhne dam shortly after midnight. Flying through heavy anti-aircraft fire, he dropped his bomb slightly off target. It burst on the reservoir bank just to the left of the huge dam. Gibson was followed by the second Lancaster, flown by Flight Lieutenant Hopgood. He dropped his bomb too late. The bomb bounced over the dam and wrecked the power station behind it. Hopgood’s Lancaster was severely damaged by anti-aircraft fire and after another five kilometres it exploded mid-air and went down in flames. Before the mission, Hopgood predicted he wouldn’t survive the assault, a prophecy that eerily enough came true.

Eder Dam

The third bomb missed the Möhne dam altogether, but the fourth and fifth hit their target the way they were supposed to. The explosions blasted an opening in the dam and water immediately started pouring through the gap. Upon realising the target was hit Gibson transmitted the codeword for success, the name of his black labrador which so happened to have been killed earlier that day. He guided the three remaining aircraft with bombs to the Eder, while the others headed home.

The first two planes that were meant to bomb the Eder dam missed. The third bouncing bomb, however, managed to create a massive hole in it. Water immediately started pouring through. The flood ended up killing 1294 people, including a lot of Allied prisoners of war held in the area. Having lost two planes and punching two holes in the dams, the pilots considered the initial part of their mission a success.

The Möhne Dam following the attacks

The second wave attacking the Sorpe, bumped into early trouble. Soon after they embarked on their mission, two Lancasters already had to return. Anti-aircraft guns shot down another and a fourth crashed after hitting a power cable. Only one Lancaster, the T for Tommy, piloted by the American McCarthy, reached the Sorpe dam. This dam had sloping earth sides, in contrast to the easier bombable other dams. McCarthy had to fly lengthways across the crest of the dam to drop his bomb directly on top of it.

The approach to the Sorpe, sliding over a hillside village, was so complicated that it took McCarthy ten tries before he finally released his bomb. It hit the top of the dam but didn’t breach it – and there were no other Lancasters to follow up anymore. This meant the reserve group, who had lost two Lancasters already due to anti-aircraft fire and a third that had to return, to try and bomb the Sorpe. The first bomb dropped on it, similar to that of McCarthy, didn’t crack open the top of the dam. The second Lancaster didn’t even try it and attacked one of the secondary targets, the Ennepe. This attack too failed. This Lancaster was the last one to return to base at 6:15 AM, over nine hours after the initial wave of Lancasters took off.

Another angle of the Möhne dam

Upon return there was a debriefing with Air Marshal Harris and Barnes Wallis. In all, eight of the 19 Lancasters had been lost during the operation. It led to 56 casualties, and by the end of the war it became clear only three survived as POWs. Immediately following the mission, Gibson was awarded a Victoria Cross, and many men that participated too received medals. The Dam Busters’ Raid has assumed legendary status, and at the time gave an enormous morale boost to the British and Allied powers as a whole.

So it begs the question, since the mission is perhaps one of the most well-known missions of the Second World War: how successful was it? In the Ruhr area, water output was restored within five weeks, and the Germans had offset the loss of electricity generating power by diverting supplies from elsewhere. But, the destruction of farmland, mines, bridges and machinery, so basically the destruction of the surrounding infrastructure due to the dams busting, diverted a considerable amount of Germany’s already overstretched manpower resources to the clean-up operation. 

After this baptism of fire Gibson’s 617 Squadron went on to perform many more precision-bombing operations. This included the attack which sank the battleship Tirpitz in November 1944. The squadron lived on after the war and, in the 1980s, 617 became the RAF’s first Tornado squadron, referring to the twelve Panavia Tornado GR1s the squadron was re-equipped with. 

After this operation, Wallis’s bouncing bomb was never used again. Yet he did go on to design the Tallboy and Grand Slam bombs. These were used by 617 Squadron to destroy German railway viaducts and concrete-roofed U-boat pens. Following the Second World War, Wallis pioneered swing wings for supersonic aircraft. He passed away in 1977 at the age of 92, working on a revolutionary new airliner which could supposedly fly halfway around the world in just four hours.

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