Operation Chastise (1943): The Dambusters Raid on the Ruhr

Operation Chastise, popularly known as the Dambusters raid, was an attack by the Royal Air Force on dams in western Germany on the night of 16–17 May 1943. Nineteen modified Lancaster bombers of the newly formed No. 617 Squadron, led by Wing Commander Guy Gibson, used Barnes Wallis’s “bouncing bomb” to breach the Möhne and Eder dams. The raid became one of the most famous episodes of the Second World War, celebrated for its daring and technical ingenuity but also remembered for its heavy losses and the civilians drowned in the floods.

Background

The Ruhr valley was the industrial heart of Nazi Germany, producing much of its coal and steel. Several large dams in the surrounding hills stored water for industry, drinking supplies, canals and hydroelectric power. British planners had identified them as targets before the war, but conventional bombs could not break massive concrete or earth dams, and the reservoirs were protected by anti-torpedo nets.

Barnes Wallis, assistant chief designer at the aircraft firm Vickers-Armstrongs, worked on the problem from 1942. His answer was a weapon that would skip across the reservoir, hit the dam wall, sink against its face and explode underwater, where the water would focus the force of the blast against the structure.

Air Chief Marshal Sir Arthur Harris, head of Bomber Command, was at first sceptical. The project was approved in February 1943, and the attack had to be made by mid-May, when the reservoirs would be at their fullest.

The bouncing bomb

The weapon, codenamed Upkeep, was a cylinder about 1.5 metres long weighing around 4,200 kilograms (9,250 lb), including about 3,000 kilograms (6,600 lb) of the explosive Torpex. Mounted under a Lancaster with its bomb-bay doors removed, it was spun backwards at about 500 revolutions per minute by a motor before release.

To work, it had to be dropped from exactly 60 feet (about 18 metres) at around 220 miles per hour, roughly 400–450 yards from the dam. The crews used two spotlights angled to meet on the water at the correct height, and a simple wooden sight to judge the distance using the towers on the dam.

Wallis had tested his ideas with small models in water tanks and on reservoirs, then with full-size weapons dropped off the Kent coast at Reculver in April and May 1943. Early prototypes broke apart on hitting the water, and the final design, without its original wooden casing, was only proven days before the raid.

No. 617 Squadron

No. 617 Squadron was formed at RAF Scampton in Lincolnshire on 21 March 1943, under the 24-year-old Guy Gibson, an experienced bomber and night-fighter pilot. Its aircrew included British, Canadian, Australian, New Zealand and American airmen. For about seven weeks they practised low flying at night over lakes and reservoirs in Britain, without being told their target until the day of the raid.

The raid

On the night of 16 May 1943 nineteen Lancasters took off in three waves. Flying very low over the North Sea and the Netherlands to avoid radar, they lost several aircraft to flak, power lines and accidents before reaching Germany.

The first wave, led by Gibson, attacked the Möhne dam just after midnight. Gibson’s bomb fell short, and the second aircraft, flown by John Hopgood, was hit by flak and crashed. After further attacks by Harold “Micky” Martin and Melvin “Dinghy” Young, the fifth bomb, dropped by David Maltby, breached the dam at about 00:50 on 17 May.

Gibson then led the remaining aircraft to the Eder dam, which was undefended but surrounded by steep hills that made the approach very difficult. After several failed runs, Henry Maudslay’s bomb exploded on the parapet, badly damaging his aircraft, which was later shot down. Les Knight, an Australian, dropped the last bomb, which breached the Eder at around 01:50.

The other waves attacked the Sorpe dam, an earth embankment where the bouncing technique could not be used. Joe McCarthy, an American serving in the Royal Canadian Air Force, and later Ken Brown dropped their bombs on it without spin, damaging the crest but not breaching it. Another crew attacked a further dam, believed to be the Ennepe or the Bever, without effect.

Eight of the nineteen Lancasters were lost. Of 133 aircrew, 53 were killed and 3 became prisoners of war.

The floods

Water from the Möhne poured down the Möhne and Ruhr valleys, and the Eder flood swept towards Kassel. Bridges, factories, power stations, houses and farms were destroyed and coal mines flooded.

The death toll on the ground is usually estimated at about 1,600 people, and some counts are higher. More than half were foreign forced labourers and prisoners of war, especially Soviet women held in a labour camp at Neheim below the Möhne dam.

Consequences

In Britain the raid was a propaganda triumph. Gibson received the Victoria Cross, and 34 members of the squadron were decorated. Photographs of the broken dams were published worldwide and helped convince American and Soviet allies of the effectiveness of British air power.

The material effect was more limited. Water and power supplies to the Ruhr were disrupted and production fell for some weeks, but the Germans repaired the Möhne and Eder dams by the autumn of 1943, using thousands of workers of the Organisation Todt, some diverted from building the Atlantic Wall. Albert Speer, the German armaments minister, later wrote that a simultaneous attack on the Sorpe and follow-up raids on the repair work could have done far greater damage. The RAF did not attack the dams again.

No. 617 Squadron remained a specialist precision unit for the rest of the war, and, together with No. 9 Squadron, sank the battleship Tirpitz in November 1944. Gibson was killed in September 1944 when his aircraft crashed in the Netherlands.

Myths and facts

A popular belief is that the raid crippled German war production. In reality the Ruhr’s output recovered quickly, though the attack did force Germany to spend labour and materials on repairs and on defending other dams.

Another misconception is that the bomb bounced into the dam and exploded on impact. It was designed to bounce over the water, hit the wall, roll down the face and explode about 30 feet below the surface, using a hydrostatic fuse.

Timeline

• 1942: Barnes Wallis develops the bouncing bomb concept and tests scale models.
• 1943, 26 February: The Upkeep project is approved.
• 1943, 21 March: No. 617 Squadron is formed at RAF Scampton.
• 1943, 16 May, about 21:30: The first Lancasters take off from Scampton.
• 1943, 17 May, about 00:50: The Möhne dam is breached.
• 1943, 17 May, about 01:50: The Eder dam is breached.
• 1943, September–October: The Möhne and Eder dams are repaired.

Legacy

Paul Brickhill’s book The Dam Busters (1951) and the 1955 film of the same name, with its well-known march by Eric Coates, made the raid a lasting part of British popular memory. Historians today usually present it as a remarkable feat of engineering and airmanship whose strategic results fell short of its fame, set against the wider strategic bombing campaign that included the bombing of Hamburg later that year and the bombing of Dresden in 1945. In Germany, memorials at the dams and in Neheim remember the people drowned in the floods.

Why it matters

Operation Chastise showed how new technology and specialist training could make precision attacks possible in an era of area bombing. It also illustrates the human cost of strategic bombing on both sides: the young aircrew who died and the civilians and forced labourers killed below the dams.