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 mainly Soviet forced labourers – died. Despite rapid repairs by the Germans, production did not return to normal until September.