Möhnesee is a municipality in the district of Soest, in North Rhine-Westphalia, Germany. The Möhnesee municipality is situated around the Möhne Reservoir, approx. 10 km south of Soest. On the night of the 16/17 May 1943, the Dam which contains the Mohnesee was breached in an attack by Avro Lancaster Bombers of 617 Squadron of the British Ro…Möhnesee is a municipality in the district of Soest, in North Rhine-Westphalia, Germany. The Möhnesee municipality is situated around the Möhne Reservoir, approx. 10 km south of Soest. On the night of the 16/17 May 1943, the Dam which contains the Mohnesee was breached in an attack by Avro Lancaster Bombers of 617 Squadron of the British Royal Air Force, the "Dambusters".