Operation Chastise Bombs Dams to Paralyze War Industries

London, England · May 16, 1943

At least since 1937, 2 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./4,196 kilograms payload of 1 externally mounted, specially designed “bouncing bomb” (actually a revolving depth charge codenamed Upkeep), flew toward 3 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/18.2 meters, 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 2 of the 3 targeted dams. The Moehne dam alone spilled around 330 million tons of water (87 percent of its reservoir) into the western Ruhr region, devastating factories, homes, mines, bridges, roads, pumping stations, and farmland for miles/kilometers around. Some farmland remained effectively unusable until the 1950s. The loss of the 2 dam power plants and the destruction of 7 others interrupted hydroelectric power generation for about 2 weeks. The greatest impact was felt, as intended, on the Ruhr’s munitions industry. German leader Adolf Hitler dispatched 7,000 workers to clean up the damage and begin rebuilding the dams. He also approved the transfer of an additional 20,000 workers, many from Atlantic Wall projects, to assist with the dam repairs, which were completed 5 months later for a loss of as little as 5 percent of armament production in the latter half of 1943. Strangely, the RAF, at a cost of 8 Lancasters and 53 crew members 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.”

Operation Chastise: Busting Dams in Germany’s Industrial Heartland

Operation Chastise: Moehne dam breach, North Rhine-Westphalia, May 17, 1943

Operation Chastise: Eder dam breach, North Rhine-Westphalia, May 1943

Left: The The Moehne dam breached, photographed by an RAF pilot on May 17, 1943, 1 day after RAF 617 Squadron had attacked the dam with their cylindrical bombs. Six barrage balloons can be seen above the dam. The 2 direct hits on the concrete-and-steel gravity Moehne dam resulted in a breach around 250 ft. wide/76 meters and 292 ft./89 meters deep. A torrent of water around 32.5 ft. high and traveling at around 15 mph/24 km/h swept through the valleys of the Moehne and Ruhr rivers in North Rhine-Westphalia, extending for around 50 miles/80 kilometers from the source.

Right: The Eder dam, the largest in Europe, was also breached in 2 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.