Operation Chastise

Operation Chastise was an attack on German dams carried out on 16–17 May 1943 by Royal Air Force No. 617 Squadron, later called the Dam Busters, using a purpose-built "bouncing bomb" developed by Barnes Wallis. The Möhne and Edersee dams were breached, causing catastrophic flooding of the Ruhr valley and of villages in the Eder valley; the Sorpe Dam sustained only minor damage. Two hydroelectric power stations were destroyed and several more damaged. Factories and mines were also damaged and destroyed. An estimated 1,600 civilians - about 600 Germans and 1,000 forced labourers, mainly Soviet - died. Despite rapid repairs by the Germans, production did not return to normal until September.

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The mission grew out of a concept for a bomb designed by Barnes Wallis, assistant chief designer at Vickers. He devised a bomb (more accurately, a mine) in the shape of a cylinder, equivalent to a very large depth charge. It was designed with backward spin of 500rpm. When dropped it would skip across the surface of the water before hitting the dam wall as its speed slowed. After submerging, it would run down the side of the dam towards its base, thus maximising the explosive effect against the dam. This weapon was code named 'Upkeep'.

Testing of the concept included blowing up a scale model dam and then the breaching of the disused Nant-y-Gro dam in Wales. 30 Lancasters were to be allocated to the mission and the target date was set for May, when water levels would be at their highest and breaches in the dams would cause the most damage. With eight weeks to go the modifications needed to the Lancasters had yet to be designed.

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In late March 1943, a new squadron was formed to carry out the raid on the dams. Initially codenamed Squadron X, 617 Squadron was led by 24 year old Wing Commander Guy Gibson and was made up of aircrew from Britain, Canada, Australia, New Zealand and the USA. With one month to go before the raid, and with only Gibson knowing the full details of the operation, the squadron began intensive training in low-level night flying and navigation.

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The targets selected were the Möhne Dam and the Sorpe Dam, upstream from the Ruhr industrial area and the Edersee Dam on the Eder River.

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Bombing from an altitude of 60ft, at an air speed of 240mph called for expert crews and intensive flight training began. There were also technical problems to solve, the first one being to determine when the aircraft was at optimum distance from its target. Both the Möhne and Edersee Dams had towers at each end. A special targeting device with two prongs, making the same angle as the two towers at the correct distance from the dam, showed when to release the bomb.

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The second problem was determining the aircraft's altitude, as the altimeters then in use lacked sufficient accuracy. Two spotlights were mounted, one under the aircraft's nose and the other under the fuselage, so that at the correct height their light beams would converge on the surface of the water. The crews practised at the Eyebrook Reservoir, near Uppingham, Rutland; Abberton Reservoir near Colchester; Derwent Reservoir in Derbyshire; and Fleet Lagoon on Chesil Beach. Wallis's bomb itself was first tested at the Elan Valley Reservoirs.

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On 16 May, 133 aircrew in 19 Lancasters took off in three waves to bomb the dams. Gibson was flying in the first wave and his aircraft was first to attack the Möhne at 12.28am, but five aircraft had to drop their bombs before it was breached. The remaining aircraft still to drop their bombs then attacked the Eder, which finally collapsed at 1.52am. Meanwhile, aircraft from the two other waves bombed the Sorpe but it remained intact.

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Of the 133 aircrew that took part, 53 men were killed and three became prisoners of war. On the ground, almost 1,300 people were killed in the resulting flooding. Although the impact on industrial production was limited, the raid gave a significant morale boost to the people of Britain.

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Bomber Command wanted a bomb damage assessment as soon as possible and the CO of 542 Squadron was informed of the estimated time of the attacks. A photo-reconnaissance Spitfire, piloted by Flying Officer Frank 'Jerry' Fray, took off from RAF Benson at 07:30 hours and arrived over the Ruhr River some hours after first light. Photos were taken of the breached dams and the huge floods.

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The pilot later described the experience:

I could see the industrial haze over the Ruhr area and

what appeared to be a cloud to the east. On flying closer,

I saw that what had seemed to be cloud was the sun shining on the flood waters. I looked down into the deep valley

which had seemed so peaceful three days before but now

it was a wide torrent. The whole valley of the river was inundated with only patches of high ground and the tops

of trees and church steeples showing above the flood.

I was overcome by the immensity of it"

Jerry Fray

Source: Wikipedia.org / IWM

Animation: Anynobody / Wikipedia • Licensed for reuse under CC BY-SA 4.0