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
Mark 26 nuclear bomb Mark 26 nuclear bomb The Mark 26 nuclear bomb was related to the Mark 21. Development of the Mk-26 started on 1 September 1954. At the end of July 1955 the design of the Mk-21 was released for production, while the design for the Mk-26 was not. The "Clean" Mk-21C which was tested in the Redwing Navajo shot did not interest the US Air Force, or AEC. As the decision not to pursue the "clean" Mk-21 closely coincided with the decision to terminate development of the Mk-26 in April 1957, it is possible that Mk-26 was the designation for the