Operation Chastise was an attack on German dams carried out on 16–17 May 1943 by Royal Air Force No. 617 Squadron, subsequently known as the "Dambusters", using a specially developed "bouncing bomb" invented and 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, while the Sorpe dam sustained only minor damage.

Prior to World War II, the British Air Ministry had identified Germany's heavily industrialised Ruhr Valley, and especially its dams, as important strategic targets: in addition to providing hydro-electric power and pure water for steel-making, they also supplied drinking water and water for the canal transport system. The methods used to attack the dams had been carefully worked out. Calculations indicated that repeated air strikes with large bombs could be effective, but required a degree of accuracy which Bomber Command had been unable to attain in the face of enemy defences.

The mission grew out of a concept for a bomb designed by Barnes Wallis and developed by his team at Vickers. Wallis was Assistant Chief Designer at Vickers. He had worked on both the Vickers Wellesley and Vickers Wellington bombers. While working on the Vickers Windsor he had also begun work, with support of the Admiralty, on a bomb designed initially for attacking ships, though dam-destruction was soon considered.