London, England · May 16, 1943

At least since 1937, two years before the out­break of Euro­pean hosti­lities, British intel­li­gence had looked into devel­oping alter­na­tive ways to de­stroy Ger­man facto­ries in the Ruhr Valley, Ger­many’s indus­trial heart­land. Late on this date in 1943 in Germany, a Brit­ish squad­ron of nine­teen modi­fied Avro Lan­caster bombers, each with a 9,250‑lb pay­load of one externally mounted, specially designed “bounc­ing bomb” (actually, a revolving depth charge), flew toward three dams on the Moehne and Eder rivers in the Ruhr Valley. The “dam­busters” in Opera­tion Chas­tise dropped their bombs into the reser­voirs when spring run­off was at its highest. Released from a height of 60 feet, the barrel-shaped bombs skipped across the water’s sur­face like stones rico­cheting across a lake, to sink and deto­nate against the face of the dam at a pre­de­fined depth. (Fitted with elec­tric motors to set them spinning back­wards to the direc­tion of travel before being released, the bombs needed to skip over the water to avoid being trapped in pro­tec­tive steel netting near the wall; spinning back­wards ensured that the bombs hugged the wall when they hit it and sank.) The spec­tac­u­lar feat of pre­ci­sion bombing, argu­ably the most auda­cious bombing raid of the Euro­pean war, breached two of the three tar­geted dams. The Moehne dam alone spilled around 330 million tons of water into the west­ern Ruhr region, devas­tating fac­tories, homes, mines, and farm­land for miles around. Some farm­land remained effec­tively un­us­able until the 1950s. The loss of the two dam power plants and the de­struc­tion of seven others inter­rupted hydro­electric power gene­ration for about two weeks. The greatest im­pact was felt, as intended, on the Ruhr’s muni­tions indus­try. Strangely, the RAF, which lost eight Lan­cas­ters in the Chastise raid, did not return to bomb the dams as they under­went repairs. Bodies of at least 1,579 vic­tims were found along the Moehne and Ruhr rivers, with hun­dreds of people gone missing. The city of Neheim was worst hit: over 800 people perished, among them some 500 female slave laborers from the Soviet Union. The drowning of thou­sands of civil­ians and POWs led to changes in the Geneva Con­ven­tion to pro­hibit simi­lar raids in the future “if such may cause release of dan­gerous forces from the works or instal­la­tions and con­se­quent severe losses on the civilian population.”

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Operation Chastise: Busting Dams in Germany’s Industrial Heartland

Moehne dam breach, North Rhine-Westphalia, May 17, 1943Eder dam breach, North Rhine-Westphalia, May 1943

Left: The Moehne dam breached, photo­graphed by an RAF pilot on May 17, 1943, one day after RAF 617 Squad­ron had attacked the dam with their cylin­dri­cal bombs. Six bar­rage bal­loons can be seen above the dam. The two direct hits on the con­crete-and-steel gra­vity Moehne dam resulted in a breach around 250 ft wide and 292 ft deep. A tor­rent of water around 32‑1/2 ft high and traveling at around 15 mph swept through the valleys of the Moehne and Ruhr rivers in North Rhine-West­phalia, extending for around 50 miles from the source.

Right: The Eder dam, the largest in Europe, was also breached in two places. The wave from the breach was not strong enough to result in sig­nif­i­cant damage by the time it reached Kassel, the largest city in north­ern Hessen. The crest of a third dam, the Sorpe dam, had a por­tion been blown off but was other­wise un­scathed, pro­tected from the Lan­cas­ters by an in­creasingly dense fog that rolled in during the raid.

The Dambuster Raids: Operation Chastise, a Documentary