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
William H. Blanchard and as chief of advanced pilot training in the Flying Training Command, before his selection in 1943 for duty with the initial B-29 bomber wing then being formed in Salina, Kansas. In 1944, Blanchard, as deputy commander of the 58th Bomb Wing, flew the first B-29 into China to begin his participation in strategic bombing operations against the Japanese mainland. Later, assigned as commander of the 40th Bomb Group (B-29) and subsequently as operations officer of the 21st Bomber Command in the Marianas, he planned and flew low-level fire raids against major Japanese targets. In the climaxing phase of World