Nuclear fission the Manhattan Project during World War II (September 1, 1939 – September 2, 1945) carried out most of the early scientific work on fission chain reactions, culminating in the three events involving fission bombs that occurred during the war. The first fission bomb, codenamed "The Gadget", was detonated during the Trinity Test in the desert of New Mexico on July 16, 1945. Two other fission bombs, codenamed "Little Boy" and "Fat Man", were used in combat against the Japanese cities of Hiroshima and Nagasaki in on August 6 and 9, 1945 respectively. Even the first fission bombs were thousands of
B28 nuclear bomb several subsequent weapons. The B28 was the mainstay of SAC during the Cold War and have yet to be completely dismantled by the Defense Department (as of 2012). Nuclear researcher Chuck Hansen's research indicates that the Python primary was used in the US B28 nuclear bomb and the W28, W40, and W49 nuclear warheads. Four Mark 28 training variants (BDU-16/E) on their transporter (MHU-7/M) are on display in the Cold War Gallery at the National Museum of the United States Air Force in Dayton, Ohio. The Canadian War Museum, in Ottawa, holds a Mark 28RE training variant in its Cold