Operation Chastise, known as the Dambusters’ Raid, was an attack by the Royal Air Force on German dams in May 1943, using revolutionary ‘bouncing bombs’.
What was the Dambusters Raid?
On the night of 16 and 17 May 1943, in one of the most daring operations of the Second World War, the RAF’s specially formed 617 Squadron attacked three main dams in Germany’s Ruhr Valley with a new secret weapon, a highly destructive ‘bouncing bomb’.
The aim was to cause catastrophic flooding in the enemy’s industrial heartland, sabotaging war production and destroying infrastructure.
The raid was celebrated as a significant military success by the Allies at the time, a powerful morale booster, but it came at great cost to human life. 53 aircrew were killed and an estimated 1,300 people drowned or were missing when the breached dams inundated a 65 kilometres stretch of the surrounding area.
Hundreds of properties were destroyed and thousands of livestock lost.
The Ruhr Valley, with its armaments factories, power plants and other industrial sites, was at the heart of the German war machine and a priority target.
A report promoted, and initially rejected, within the RAF was that to breach the largest dam, the Möhne, a low-flying aircraft would have to release a huge bomb that would hit the dam, sink and explode against it deep underwater.
The problem was that there was no such bomb and, in any case, the necessary size of such a bomb would exceed any of the RAF’s existing aircrafts’ payload.
If this strategy were to be considered, a revolutionary new type of weapon would have to be developed.
Dr Barnes Wallis and experiments with bouncing marbles
Barnes Wallis was known for thinking out of the box; developing innovative concepts in his spare time that might help the war effort.
He later said in a 1973 autobiographical article:
‘I had the idea of a missile which, if dropped on the water at a considerable distance upstream of the dam, would reach the dam in a series of ricochets, and after impact against the dam would sink in close contact with the upstream face of the masonry.’Dr Barnes Wallis
He first experimented with the idea in his own back garden using his daughter’s marbles, firing them from a home-made catapult and making them bounce across butts of water.
Early experiments and the bouncing bomb
Barnes Wallis experimented with different methods of attacking the dams, including using a scale model replica of the Möhne Dam, as well as carrying out tests in the large indoor water tanks at the National Physical Laboratory, Teddington, South-West London.
Eventually, having proved to the Ministry of Aircraft Production that his concept of a bouncing bomb was the best method of attack, experimental barrel-shaped bombs were dropped from a Wellington aircraft at Chesil Beach from December 1942 into early 1943.
In these filmed trials, the bombs initially shattered on impact with the water, but Barnes Wallis made many modifications, including adding a backspin on the bomb which improved its bouncing ability.
In subsequent trials, the bomb bounced more than twenty times and travelled over 1,200 metres.
The bouncing bomb gets the green light and undergoes further trials
To successfully breach the Möhne Dam, the bombers would have to fly at a precise tree top-brushing altitude of 60 foot (18 metres) at a speed of 232 mph, before dropping the spinning four tonne bomb at exactly 1,276 foot (389 metres) from the dam. The correct distance would be judged using a simple wooden triangular sight focused on the dam’s twin turrets, and the accurate height ascertained from two intersecting spotlights under the aircraft.
The 1.5 metre long bomb would use its reverse spin to bounce across the water surface towards the dam wall, avoiding the torpedo nets. When the bomb hit the structure, the backspin would force it downwards deep underwater where it would explode like a depth charge, breaching the dam.
At the start of 1943, Barnes Wallis showed the Chesil Beach films to the Air Ministry and to the Ministry of Aircraft Production. Full scale trials were approved, despite opposition from his employers at Vickers-Armstrong (‘silly nonsense’) and Bomber Command’s Air Chief Marshall Sir Arthur ‘Bomber’ Harris (1892 to 1984) who called the idea ‘tripe of the wildest description’.
The top brass had determined that the best time for a strategic attack on the Ruhr dams was on a moonlit night before the end of May 1943 when the reservoirs were at their fullest. This pressurised timetable meant the trials would be still running right up until that date.
Crack new air squadron formed
At the end of February 1943, while trials of the bouncing bomb were still underway, a crack Squadron of highly experienced pilots and aircrew, based at RAF Scampton in Lincolnshire, was established specifically for the attack on the dams. Hangar 2, where 617 Squadron was housed and where Guy Gibson had his office, is Listed Grade II.
The Squadron later became known as the ‘Dambusters.’
The highly secret mission was codenamed ‘Operation Chastise.’
The Squadron started daily intensive training in modified Lancaster bombers, practising low level night flying and navigation, over bodies of water and canal systems, criss-crossing the country, including Scotland. Dummy practice bombs were dropped on different reservoirs.
None of the aircrews as yet knew the reason for these operations.
On 11 April 1943, all personnel involved in the operation received a high security briefing at RAF Manston, Kent.
Guy Gibson and his Bomber Leader, Flight Lieutenant Bob Hay, were ordered to Reculver to witness the secret trials of the new bomb, before 617 Squadron practised dropping dummy Upkeeps there.
On 14 May, the Squadron’s Lancaster’s took part in a full dress rehearsal on Uppingham Lake, Rutland and Colchester Reservoir in Essex.
Bomber Command was given the final go-ahead by the Air Ministry on 15 May: Operation Chastise would begin the following day.
At 9.28pm on 16 May 1943, on a bright moonlit night, nineteen Lancaster bombers took off in three waves at ten minute intervals from RAF Scampton. 133 airmen were on board. They flew low over Europe to avoid radar detection.
Gibson led the first attack wave, releasing the bouncing bombs on the massive Möhne Dam while under attack from flak gunners in the dam towers.
Four aircraft dropped bombs, but it was not until the fifth attack that the dam was fully breached.
As the dam burst, a colossal wave of water, estimated at 10 metres high and travelling at 24 kilometres an hour, swept across the Ruhr Valley destroying everything in its path.
The remaining aircraft breached the Eder Dam after several unsuccessful attempts. It had been shrouded in fog but was undefended. The earthen Sorpe Dam remained intact. German night fighters were scrambled to try and thwart attacks, without success.
The last Lancaster landed back at base at RAF Scampton at just after 4am on 17 May, seven hours after the mission began.
Eight aircraft out of nineteen failed to return and 53 of the 133 aircrew were lost. Three others were captured and became prisoners-of-war.
In the Ruhr Valley, the catastrophic flooding spread over 65 kilometres. An estimated 1,300 people drowned or were missing, including prisoners-of-war and forced labourers incarcerated in camps, hundreds of whom were women from Ukraine, Poland and Russia. The attack caused more civilian deaths than in any previous RAF attack on Germany during the war.
Factories, power plants, mines, roads and bridges, homes and other properties were destroyed; agricultural land inundated and ruined; animals lost.
The Dambusters’ mission raised British morale. The press was triumphalist: 617 Squadron were heroes (617 later became a specialist precision bombing Squadron). Gibson was awarded the Victoria Cross. 32 other aircrew also received honours.
German morale took a battering, but industry in the Ruhr Valley was up-and-running again within a few months; an estimated 30,000 workers had been commandeered to repair the damage.
Although only two dams were breached, Operation Chastise did handicap the German war effort by the need to divert valuable resources to the area in terms of workers and anti-aircraft batteries, particularly from the Eastern Front where Germany was heavily engaged fighting the Soviet Union.
Barnes Wallis Wallis himself was appalled by the RAF casualties. He had been awarded £10,000 for his war work. In 1951, he donated the money towards a fund to help with the education of children of RAF personnel.
In 1977, the Additional Protocols 1 and II of the Geneva Convention included outlawing attacks on dams.
There are a number of memorials to the Dambusters’ raid and associated crash sites, both in Britain, the Netherlands, Germany and elsewhere.
The memorial pictured commemorates, in alphabetical order without rank but with individual honours listed, the 204 aircrew of 617 Squadron who lost their lives in different missions during the Second World War, including the 53 killed during Operation Chastise.
The inscription running across the top reads: ‘They Died for Your Freedom.’
The memorial information tells the story of the Dambusters’ raid and the rebuilding of the dam, in German and English, remembering the victims of what is known there as the ‘Möhne Catastrophe’.
The plaque reads: ‘On the night of 16/17 May 1943 Lancaster AJ-A was on the homeward flight from a raid on the German dams (Operation Chastise) to RAF Scampton. The Lancaster was hit by anti-aircraft fire and crashed about 2km south from this point along the shoreline.’
In the year following the Dambuster operation, on 19 September 1944, Gibson and his navigator Warwick were flying in a Mosquito as part of an attack on Germany. It was thought that they may have had engine problems. Their aircraft crashed around 10.30pm. Neither man survived.
The Dutch authorities laid them to rest in a local cemetery. Later the Commonwealth War Graves Commission replaced their crosses with standard headstones.
During the Second World War, Barnes Wallis also developed the enormous ‘Tallboy’ bomb used to sink the battleship, Tirpitz, flagship of the German fleet, and attack V1 rocket launch sites and U-Boat pens.
After the war, Barnes Wallis continued to lead aeronautical research and development. In 1954, he became a Fellow of the Royal Society and was knighted in 1968.
The last surviving member of 617 Squadron, Johnny Johnson, died in 2022 aged 101.
Written by Nicky Hughes.
Banner image: Illustration showing Lancaster bombers attacking the Möhne Dam, Germany, on the night of 16 and 17 May 1943. Source: Creative Commons.
- The Barnes Wallis Foundation
- The RAF Museum, Online Exhibitions: 617 Squadron and the Dams Raid
- History of Manston Airfield: Dambuster Bouncing Bomb Tests
- IWM: The Incredible Story of the Dambusters Raid
- Barnes Wallis donated the bulk of his papers to the Science Museum. Find out more.