"Royal Air Force Bomber Command, 1942-1945." Operation CHASTISE: the attack on the Moehne, Eder and Sorpe Dams by No. 617 Squadron RAF on the night of 16/17 May 1943. No. 617 Squadron practice dropping the 'Upkeep' weapon at Reculver bombing range, Kent. Second launch sequence (5): a group of observers watches as the bomb bounces toward the shoreline. Dr Barnes Wallis, on the extreme left of the group, can be seen urging the bomb on.