Heavy bomber version of the bouncing bomb, was used to destroy the Mohne and Eder dams by Lancasters from the specially recruited and trained 617 Squadron, often known as the Dambusters, under Wing Commander Guy Gibson. In March and April 1945, as the war in Europe was ending, Lancasters dropped Grand Slams and Tallboys on U-boat pens and railway viaducts across north Germany. At Bielefeld more than of railway viaduct was destroyed by Grand Slams creating an earthquake effect, which shook the foundations. The Boeing B-29 Superfortress was a development of the Fortress, but a larger design with four Wright R-3350 Duplex-Cyclone
Douglas Bradshaw He received his pilot's license in 1936. He served as a flying instructor at Camp Borden, Ontario from 1935-1939. In December 1941, he was posted overseas. From March 1942 until April 1943, Wing Commander Bradshaw commanded 420 Snowy Owl Squadron. During this time, Bradshaw led his squadron in some of the first 1000 plane bomber raids into Germany. At the end of World War II, Group Captain Bradshaw served at RCAF headquarters in Ottawa as Director of Air Operations. He was promoted to the rank of Air Commodore in January 1953. He served as Chief of Training for the RCAF.